{"transactions":[{"id":4638707,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":17821,"kind":"person","name":"Hallen Ed","position":1,"cik":"0001991125","reported_name":"Hallen Ed","relationship":{"director":true,"officer":false,"ten_percent_owner":true,"other":false}}],"security":"Series A Common Stock","published_at":"2026-10-09T20:30:19.000Z","date":"2026-10-08","kind":"gift","planned":true,"acquired":false,"shares":17885,"price":0,"value":0.0,"ownership":{"direct":false,"nature":"By Hodgkins LLC"},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F6","text":"Represents a bona fide gift of 17,885 shares of stock from Hodgkins LLC, of which Reporting Person serves as manager, to a donor-advised fund pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on June 1, 2026."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F5","text":"Shares held by Hodgkins LLC, of which the Reporting Person serves as manager. The Reporting Person disclaims Section 16 beneficial ownership of such shares except to the extent of his pecuniary interest therein, if any, and this report shall not be deemed to be an admission that he has beneficial ownership of such shares for Section 16 or any other purpose."}],"balance_after":370246,"source":{"system":"sec-edgar","filing":"0001470831-26-000934","document":"wk-form4_1791577816.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":3,"url":"https://www.sec.gov/Archives/edgar/data/1991125/000147083126000934/wk-form4_1791577816.xml","form_type":"4"}},{"id":4638706,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":17821,"kind":"person","name":"Hallen Ed","position":1,"cik":"0001991125","reported_name":"Hallen Ed","relationship":{"director":true,"officer":false,"ten_percent_owner":true,"other":false}}],"security":"Series A Common Stock","published_at":"2026-10-09T20:30:19.000Z","date":"2026-10-07","kind":"sale","planned":true,"acquired":false,"shares":58815,"price":17.4,"value":1023381.0,"ownership":{"direct":false,"nature":"By Hodgkins LLC"},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on June 1, 2026."},{"field":"price","element":"transactionPricePerShare","label":"F4","text":"The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $17.00 to $17.63 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F5","text":"Shares held by Hodgkins LLC, of which the Reporting Person serves as manager. The Reporting Person disclaims Section 16 beneficial ownership of such shares except to the extent of his pecuniary interest therein, if any, and this report shall not be deemed to be an admission that he has beneficial ownership of such shares for Section 16 or any other purpose."}],"balance_after":388131,"source":{"system":"sec-edgar","filing":"0001470831-26-000934","document":"wk-form4_1791577816.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1991125/000147083126000934/wk-form4_1791577816.xml","form_type":"4"}},{"id":4638705,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":17821,"kind":"person","name":"Hallen Ed","position":1,"cik":"0001991125","reported_name":"Hallen Ed","relationship":{"director":true,"officer":false,"ten_percent_owner":true,"other":false}}],"security":"Series A Common Stock","published_at":"2026-10-09T20:30:19.000Z","date":"2026-10-07","kind":"sale","planned":true,"acquired":false,"shares":38667,"price":17.4,"value":672805.8,"ownership":{"direct":false,"nature":"By Hodgkins Trust"},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on June 1, 2026."},{"field":"price","element":"transactionPricePerShare","label":"F2","text":"The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $17.03 to $17.63 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F3","text":"Shares are owned directly by Hodgkins Trust for the benefit of the Reporting Person and the Reporting Person's family, and of which the trustee is an independent institution. The Reporting Person disclaims Section 16 beneficial ownership of such shares except to the extent of his pecuniary interest therein, if any, and this report shall not be deemed to be an admission that he has beneficial ownership of such shares for Section 16 or any other purpose."}],"balance_after":55290,"source":{"system":"sec-edgar","filing":"0001470831-26-000934","document":"wk-form4_1791577816.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1991125/000147083126000934/wk-form4_1791577816.xml","form_type":"4"}},{"id":4627177,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":17821,"kind":"person","name":"Hallen Ed","position":1,"cik":"0001991125","reported_name":"Hallen Ed","relationship":{"director":true,"officer":false,"ten_percent_owner":true,"other":false}}],"security":"Series A Common Stock","published_at":"2026-09-25T21:50:51.000Z","date":"2026-09-24","kind":"sale","planned":true,"acquired":false,"shares":800,"price":17.02,"value":13616.0,"ownership":{"direct":false,"nature":"By Hodgkins LLC"},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on June 1, 2026."},{"field":"price","element":"transactionPricePerShare","label":"F2","text":"The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $17.00 to $17.03 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F4","text":"Shares held by Hodgkins LLC, of which the Reporting Person serves as manager. The Reporting Person disclaims Section 16 beneficial ownership of such shares except to the extent of his pecuniary interest therein, if any, and this report shall not be deemed to be an admission that he has beneficial ownership of such shares for Section 16 or any other purpose."}],"balance_after":446946,"source":{"system":"sec-edgar","filing":"0001470831-26-000904","document":"wk-form4_1790373048.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1991125/000147083126000904/wk-form4_1790373048.xml","form_type":"4"}},{"id":4627176,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":17821,"kind":"person","name":"Hallen Ed","position":1,"cik":"0001991125","reported_name":"Hallen Ed","relationship":{"director":true,"officer":false,"ten_percent_owner":true,"other":false}}],"security":"Series A Common Stock","published_at":"2026-09-25T21:50:51.000Z","date":"2026-09-24","kind":"sale","planned":true,"acquired":false,"shares":500,"price":17.02,"value":8510.0,"ownership":{"direct":false,"nature":"By Hodgkins Trust"},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on June 1, 2026."},{"field":"price","element":"transactionPricePerShare","label":"F2","text":"The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $17.00 to $17.03 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F3","text":"Shares are owned directly by Hodgkins Trust for the benefit of the Reporting Person and the Reporting Person's family, and of which the trustee is an independent institution. The Reporting Person disclaims Section 16 beneficial ownership of such shares except to the extent of his pecuniary interest therein, if any, and this report shall not be deemed to be an admission that he has beneficial ownership of such shares for Section 16 or any other purpose."}],"balance_after":93957,"source":{"system":"sec-edgar","filing":"0001470831-26-000904","document":"wk-form4_1790373048.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1991125/000147083126000904/wk-form4_1790373048.xml","form_type":"4"}},{"id":4622034,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":18048,"kind":"person","name":"Smith Erica Ellen","position":1,"cik":"0002050221","reported_name":"Smith Erica Ellen","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Chief Financial Officer"}}],"security":"Series A Common Stock","published_at":"2026-09-17T22:14:42.000Z","date":"2026-09-15","kind":"grant","planned":false,"acquired":true,"shares":328767,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"shares","element":"transactionShares","label":"F2","text":"Represents performance stock units (\"PSUs\") awarded under the Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement. The PSUs will vest in up to three tranches over a two and a half year measurement period, subject to the achievement of specified performance targets tied to the trading price of the Series A Common Stock and the Reporting Person's continued service in the same or substantially equivalent position as the Reporting Person held as of the grant date through the applicable vesting date. Each tranche of PSUs will vest only if the average closing price of the Series A Common Stock for a period of at least sixty consecutive calendar days is at or above a specified dollar value during the applicable measurement period."},{"field":"shares","element":"transactionShares","label":"F3","text":"(continued) The stock price targets for tranches 1 through 3 are $30.00, $50.00, and $75.00 per share, respectively, subject to proportionate adjustment in the event of any stock split or other similar change in the Issuer's capital stock."},{"field":"balance_after","element":"sharesOwnedFollowingTransaction","label":"F4","text":"Consists of (i) 821,917 unvested RSUs awarded under the Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement; and (ii) 328,767 unvested PSUs awarded under the Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement."}],"balance_after":1150684,"source":{"system":"sec-edgar","filing":"0001470831-26-000890","document":"wk-form4_1789683279.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/2050221/000147083126000890/wk-form4_1789683279.xml","form_type":"4"}},{"id":4622033,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":18048,"kind":"person","name":"Smith Erica Ellen","position":1,"cik":"0002050221","reported_name":"Smith Erica Ellen","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Chief Financial Officer"}}],"security":"Series A Common Stock","published_at":"2026-09-17T22:14:42.000Z","date":"2026-09-15","kind":"grant","planned":false,"acquired":true,"shares":821917,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"shares","element":"transactionShares","label":"F1","text":"Represents restricted stock units (\"RSUs\") awarded under the Issuer's 2023 Stock Option and Incentive Plan (the \"Plan\"), each representing the contingent right to receive one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), upon vesting and settlement. The RSUs will vest in sixteen equal quarterly installments, with the first such installment vesting on February 15, 2027, subject to the Reporting Person's continued service on each such vesting date."}],"balance_after":821917,"source":{"system":"sec-edgar","filing":"0001470831-26-000890","document":"wk-form4_1789683279.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/2050221/000147083126000890/wk-form4_1789683279.xml","form_type":"4"}},{"id":4617097,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":39277,"kind":"person","name":"St. Ledger Susan","position":1,"cik":"0001673606","reported_name":"St. Ledger Susan","relationship":{"director":true,"officer":false,"ten_percent_owner":false,"other":false}}],"security":"Series A Common Stock","published_at":"2026-09-14T20:49:23.000Z","date":"2026-09-11","kind":"sale","planned":true,"acquired":false,"shares":2328,"price":15.93,"value":37085.04,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on June 12, 2026."},{"field":"balance_after","element":"sharesOwnedFollowingTransaction","label":"F2","text":"Consists of (i) 8,611 shares of Series A Common Stock and (ii) 14,822 unvested restricted stock units awarded under the Issuer's 2023 Stock Option and Incentive Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement."}],"balance_after":23433,"source":{"system":"sec-edgar","filing":"0001470831-26-000885","document":"wk-form4_1789418960.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1835830/000147083126000885/wk-form4_1789418960.xml","form_type":"4"}},{"id":670764,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":17821,"kind":"person","name":"Hallen Ed","position":1,"cik":"0001991125","reported_name":"Hallen Ed","relationship":{"director":true,"officer":false,"ten_percent_owner":true,"other":false}}],"security":"Series A Common Stock","published_at":"2026-09-02T00:18:54.000Z","date":"2026-08-31","kind":"gift","planned":true,"acquired":false,"shares":17885,"price":0,"value":0.0,"ownership":{"direct":false,"nature":"By Hodgkins LLC"},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F6","text":"Represents a bona fide gift of 17,885 shares of stock from Hodgkins LLC, of which Reporting Person serves as manager, to a donor-advised fund pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on June 1, 2026."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F5","text":"Shares held by Hodgkins LLC, of which the Reporting Person serves as manager. The Reporting Person disclaims Section 16 beneficial ownership of such shares except to the extent of his pecuniary interest therein, if any, and this report shall not be deemed to be an admission that he has beneficial ownership of such shares for Section 16 or any other purpose."}],"balance_after":447746,"source":{"system":"sec-edgar","filing":"0001470831-26-000870","document":"wk-form4_1788308332.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":3,"url":"https://www.sec.gov/Archives/edgar/data/1835830/000147083126000870/wk-form4_1788308332.xml","form_type":"4"}},{"id":670763,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":17821,"kind":"person","name":"Hallen Ed","position":1,"cik":"0001991125","reported_name":"Hallen Ed","relationship":{"director":true,"officer":false,"ten_percent_owner":true,"other":false}}],"security":"Series A Common Stock","published_at":"2026-09-02T00:18:54.000Z","date":"2026-08-31","kind":"sale","planned":true,"acquired":false,"shares":59615,"price":20.49,"value":1221511.35,"ownership":{"direct":false,"nature":"By Hodgkins LLC"},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on June 1, 2026."},{"field":"price","element":"transactionPricePerShare","label":"F4","text":"The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $20.30 to $20.78 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F5","text":"Shares held by Hodgkins LLC, of which the Reporting Person serves as manager. The Reporting Person disclaims Section 16 beneficial ownership of such shares except to the extent of his pecuniary interest therein, if any, and this report shall not be deemed to be an admission that he has beneficial ownership of such shares for Section 16 or any other purpose."}],"balance_after":465631,"source":{"system":"sec-edgar","filing":"0001470831-26-000870","document":"wk-form4_1788308332.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1835830/000147083126000870/wk-form4_1788308332.xml","form_type":"4"}},{"id":670762,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":17821,"kind":"person","name":"Hallen Ed","position":1,"cik":"0001991125","reported_name":"Hallen Ed","relationship":{"director":true,"officer":false,"ten_percent_owner":true,"other":false}}],"security":"Series A Common Stock","published_at":"2026-09-02T00:18:54.000Z","date":"2026-08-31","kind":"sale","planned":true,"acquired":false,"shares":39167,"price":20.47,"value":801748.49,"ownership":{"direct":false,"nature":"By Hodgkins Trust"},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on June 1, 2026."},{"field":"price","element":"transactionPricePerShare","label":"F2","text":"The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $20.30 to $20.77 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F3","text":"Shares are owned directly by Hodgkins Trust for the benefit of the Reporting Person and the Reporting Person's family, and of which the trustee is an independent institution. The Reporting Person disclaims Section 16 beneficial ownership of such shares except to the extent of his pecuniary interest therein, if any, and this report shall not be deemed to be an admission that he has beneficial ownership of such shares for Section 16 or any other purpose."}],"balance_after":94457,"source":{"system":"sec-edgar","filing":"0001470831-26-000870","document":"wk-form4_1788308332.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1835830/000147083126000870/wk-form4_1788308332.xml","form_type":"4"}},{"id":671383,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":18020,"kind":"person","name":"Edmond Landon","position":1,"cik":"0001991399","reported_name":"Edmond Landon","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Chief Legal Officer"}}],"security":"Series A Common Stock","published_at":"2026-09-02T00:16:27.000Z","date":"2026-08-31","kind":"sale","planned":true,"acquired":false,"shares":8103,"price":20.44,"value":165625.32,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F3","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on June 1, 2026."},{"field":"price","element":"transactionPricePerShare","label":"F4","text":"The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $19.95 to $20.77 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."},{"field":"balance_after","element":"sharesOwnedFollowingTransaction","label":"F5","text":"Consists of (i) 50,886 shares of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), (ii) 297,110 unvested restricted stock units awarded under the Issuer's 2023 Stock Option and Incentive Plan (the \"Plan\"), each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement, and (iii) 129,870 unvested performance stock units awarded under the Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement."}],"balance_after":477866,"source":{"system":"sec-edgar","filing":"0001470831-26-000868","document":"wk-form4_1788308184.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1991399/000147083126000868/wk-form4_1788308184.xml","form_type":"4"}},{"id":671382,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":18020,"kind":"person","name":"Edmond Landon","position":1,"cik":"0001991399","reported_name":"Edmond Landon","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Chief Legal Officer"}}],"security":"Series A Common Stock","published_at":"2026-09-02T00:16:27.000Z","date":"2026-08-28","kind":"sale","planned":true,"acquired":false,"shares":53473,"price":20.01,"value":1069994.73,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on August 21, 2025."},{"field":"price","element":"transactionPricePerShare","label":"F2","text":"The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $20.00 to $20.15 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."}],"balance_after":485969,"source":{"system":"sec-edgar","filing":"0001470831-26-000868","document":"wk-form4_1788308184.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1991399/000147083126000868/wk-form4_1788308184.xml","form_type":"4"}},{"id":671826,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":18319,"kind":"organization","name":"Shopify Strategic Holdings 3 LLC","position":1,"cik":"0001993562","reported_name":"Shopify Strategic Holdings 3 LLC","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":2851,"kind":"organization","name":"SHOPIFY INC.","position":2,"cik":"0001594805","reported_name":"SHOPIFY INC.","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}}],"security":"Series B Common Stock","published_at":"2026-08-31T21:35:21.000Z","date":"2026-08-31","kind":"other","planned":false,"acquired":true,"shares":344383,"price":0.01,"value":3443.83,"ownership":{"direct":true},"footnotes":[{"field":"derivative.exercise_price","element":"conversionOrExercisePrice","label":"F3","text":"Each share of Series B Common Stock is convertible at any time at the option of the holder into one share of Series A Common Stock of the Issuer, and will automatically convert into Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F3","text":"Each share of Series B Common Stock is convertible at any time at the option of the holder into one share of Series A Common Stock of the Issuer, and will automatically convert into Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"derivative.expiration_date","element":"expirationDate","label":"F3","text":"Each share of Series B Common Stock is convertible at any time at the option of the holder into one share of Series A Common Stock of the Issuer, and will automatically convert into Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"ownership.direct","element":"directOrIndirectOwnership","label":"F2","text":"Reflects securities held directly by Shopify Strategic Holdings 3 LLC, a wholly-owned subsidiary of Shopify Inc. (\"Shopify\"). Shopify is an indirect beneficial owner and disclaims beneficial ownership except to the extent of its pecuniary interest therein."}],"balance_after":17317491,"derivative":{"underlying":"Series A Common Stock","underlying_shares":344383},"source":{"system":"sec-edgar","filing":"0001193125-26-377117","document":"ownership.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1594805/000119312526377117/ownership.xml","form_type":"4"}},{"id":671825,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":18319,"kind":"organization","name":"Shopify Strategic Holdings 3 LLC","position":1,"cik":"0001993562","reported_name":"Shopify Strategic Holdings 3 LLC","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":2851,"kind":"organization","name":"SHOPIFY INC.","position":2,"cik":"0001594805","reported_name":"SHOPIFY INC.","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}}],"security":"Warrants to Purchase Series B Common Stock (Right to Buy)","published_at":"2026-08-31T21:35:21.000Z","date":"2026-08-31","kind":"other","planned":false,"acquired":false,"shares":344383,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"derivative.exercise_date","element":"exerciseDate","label":"F1","text":"25% of the shares subject to the warrants vested on July 28, 2022, and the remaining shares vest quarterly in equal amounts through July 28, 2027. Notwithstanding the foregoing, in connection with the Issuer's initial public offering (\"IPO\"), 25% of the total number of shares subject to the warrants vested immediately prior to the completion of the IPO."},{"field":"ownership.direct","element":"directOrIndirectOwnership","label":"F2","text":"Reflects securities held directly by Shopify Strategic Holdings 3 LLC, a wholly-owned subsidiary of Shopify Inc. (\"Shopify\"). Shopify is an indirect beneficial owner and disclaims beneficial ownership except to the extent of its pecuniary interest therein."}],"balance_after":1377529,"derivative":{"exercise_price":0.01,"expiration_date":"2032-07-28","underlying":"Series B Common Stock","underlying_shares":344383},"source":{"system":"sec-edgar","filing":"0001193125-26-377117","document":"ownership.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1594805/000119312526377117/ownership.xml","form_type":"4"}},{"id":683596,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":22257,"kind":"person","name":"Fernandez Gomez Luciano","position":1,"cik":"0001730978","reported_name":"Fernandez Gomez Luciano","relationship":{"director":true,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Co-Chief Executive Officer"}}],"security":"Series B Common Stock","published_at":"2026-08-19T00:09:21.000Z","date":"2026-08-15","kind":"exercise","planned":false,"acquired":false,"shares":7001,"price":18.49,"value":129448.49,"ownership":{"direct":true},"footnotes":[{"field":"derivative.exercise_price","element":"conversionOrExercisePrice","label":"F2","text":"Each share of Series B Common Stock is convertible at any time at the option of the holder into one share of Series A Common Stock of the Issuer, and will automatically convert into Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"kind","element":"transactionCoding","label":"F1","text":"Represents 7,001 shares of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), automatically converted into shares of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), in connection with tax withholding obligations related to the vesting and settlement of restricted stock units (\"RSUs\")."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F2","text":"Each share of Series B Common Stock is convertible at any time at the option of the holder into one share of Series A Common Stock of the Issuer, and will automatically convert into Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"derivative.expiration_date","element":"expirationDate","label":"F2","text":"Each share of Series B Common Stock is convertible at any time at the option of the holder into one share of Series A Common Stock of the Issuer, and will automatically convert into Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"balance_after","element":"sharesOwnedFollowingTransaction","label":"F5","text":"Consists of 48,999 shares of Series B Common Stock."}],"balance_after":48999,"derivative":{"underlying":"Series A Common Stock","underlying_shares":7001},"source":{"system":"sec-edgar","filing":"0001470831-26-000845","document":"wk-form4_1787098158.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":3,"url":"https://www.sec.gov/Archives/edgar/data/1730978/000147083126000845/wk-form4_1787098158.xml","form_type":"4"}},{"id":683595,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":22257,"kind":"person","name":"Fernandez Gomez Luciano","position":1,"cik":"0001730978","reported_name":"Fernandez Gomez Luciano","relationship":{"director":true,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Co-Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2026-08-19T00:09:21.000Z","date":"2026-08-15","kind":"tax_withholding","planned":false,"acquired":false,"shares":29133,"price":18.49,"value":538669.17,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F3","text":"Represents shares of Series A Common Stock withheld by the Issuer to satisfy tax withholding obligations in connection with the vesting and settlement of RSUs."},{"field":"balance_after","element":"sharesOwnedFollowingTransaction","label":"F4","text":"Consists of (i) 287,984 shares of Series A Common Stock; (ii) 820,351 unvested RSUs awarded under the Issuer's 2023 Stock Option and Incentive Plan (the \"Plan\"), each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement; and (iii) 1,193,238 unvested performance stock units awarded under the Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement."}],"balance_after":2301573,"source":{"system":"sec-edgar","filing":"0001470831-26-000845","document":"wk-form4_1787098158.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1730978/000147083126000845/wk-form4_1787098158.xml","form_type":"4"}},{"id":683594,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":22257,"kind":"person","name":"Fernandez Gomez Luciano","position":1,"cik":"0001730978","reported_name":"Fernandez Gomez Luciano","relationship":{"director":true,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Co-Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2026-08-19T00:09:21.000Z","date":"2026-08-15","kind":"exercise","planned":false,"acquired":true,"shares":7001,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"Represents 7,001 shares of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), automatically converted into shares of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), in connection with tax withholding obligations related to the vesting and settlement of restricted stock units (\"RSUs\")."},{"field":"price","element":"transactionPricePerShare","label":"F2","text":"Each share of Series B Common Stock is convertible at any time at the option of the holder into one share of Series A Common Stock of the Issuer, and will automatically convert into Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."}],"balance_after":2330706,"source":{"system":"sec-edgar","filing":"0001470831-26-000845","document":"wk-form4_1787098158.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1730978/000147083126000845/wk-form4_1787098158.xml","form_type":"4"}},{"id":683808,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":18020,"kind":"person","name":"Edmond Landon","position":1,"cik":"0001991399","reported_name":"Edmond Landon","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Chief Legal Officer"}}],"security":"Series A Common Stock","published_at":"2026-08-19T00:06:54.000Z","date":"2026-08-15","kind":"tax_withholding","planned":false,"acquired":false,"shares":22342,"price":18.49,"value":413103.58,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"Represents shares of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), withheld by the Issuer to satisfy tax withholding obligations in connection with the vesting and settlement of restricted stock units (\"RSUs\")."},{"field":"balance_after","element":"sharesOwnedFollowingTransaction","label":"F2","text":"Consists of (i) 112,462 shares of Series A Common Stock; (ii) 297,110 unvested RSUs awarded under the Issuer's 2023 Stock Option and Incentive Plan (the \"Plan\"), each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement; and (iii) 129,870 unvested performance stock units awarded under the Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement."}],"balance_after":539442,"source":{"system":"sec-edgar","filing":"0001470831-26-000843","document":"wk-form4_1787098011.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1991399/000147083126000843/wk-form4_1787098011.xml","form_type":"4"}},{"id":683598,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":22259,"kind":"person","name":"Galvin Carmel","position":1,"cik":"0001733091","reported_name":"Galvin Carmel","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Chief People Officer"}}],"security":"Series A Common Stock","published_at":"2026-08-19T00:05:25.000Z","date":"2026-08-15","kind":"tax_withholding","planned":false,"acquired":false,"shares":30541,"price":18.49,"value":564703.09,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"Represents shares of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), withheld by the Issuer to satisfy tax withholding obligations in connection with the vesting and settlement of restricted stock units (\"RSUs\")."},{"field":"balance_after","element":"sharesOwnedFollowingTransaction","label":"F2","text":"Consists of (i) 195,731 shares of Series A Common Stock; (ii) 549,390 unvested RSUs awarded under the Issuer's 2023 Stock Option and Incentive Plan (the \"Plan\"), each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement; and (iii) 162,337 unvested performance stock units awarded under the Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement."}],"balance_after":907458,"source":{"system":"sec-edgar","filing":"0001470831-26-000841","document":"wk-form4_1787097923.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1733091/000147083126000841/wk-form4_1787097923.xml","form_type":"4"}},{"id":682533,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":21993,"kind":"person","name":"Whalen Amanda","position":1,"cik":"0001991131","reported_name":"Whalen Amanda","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Chief Financial Officer"}}],"security":"Series A Common Stock","published_at":"2026-08-19T00:02:54.000Z","date":"2026-08-15","kind":"tax_withholding","planned":true,"acquired":false,"shares":28950,"price":18.49,"value":535285.5,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F3","text":"Represents shares of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\") withheld by the Issuer to satisfy tax withholding obligations in connection with the vesting and settlement of restricted stock units (\"RSUs\")."},{"field":"balance_after","element":"sharesOwnedFollowingTransaction","label":"F4","text":"Consists of (i) 89,917 shares of Series A Common Stock; (ii) 478,053 unvested RSUs awarded under the Issuer's 2023 Stock Option and Incentive Plan (the \"Plan\"), each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement; and (iii) 227,272 unvested performance stock units awarded under the Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement."}],"balance_after":795242,"source":{"system":"sec-edgar","filing":"0001470831-26-000839","document":"wk-form4_1787097772.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1835830/000147083126000839/wk-form4_1787097772.xml","form_type":"4"}},{"id":682532,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":21993,"kind":"person","name":"Whalen Amanda","position":1,"cik":"0001991131","reported_name":"Whalen Amanda","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Chief Financial Officer"}}],"security":"Series A Common Stock","published_at":"2026-08-19T00:02:54.000Z","date":"2026-08-14","kind":"sale","planned":true,"acquired":false,"shares":14000,"price":18.47,"value":258580.0,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on August 21, 2025."},{"field":"price","element":"transactionPricePerShare","label":"F2","text":"The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $18.25 to $18.82 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."}],"balance_after":824192,"source":{"system":"sec-edgar","filing":"0001470831-26-000839","document":"wk-form4_1787097772.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1835830/000147083126000839/wk-form4_1787097772.xml","form_type":"4"}},{"id":688504,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":23867,"kind":"organization","name":"SUMMIT PARTNERS L P","position":1,"cik":"0000830588","reported_name":"SUMMIT PARTNERS L P","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":23868,"kind":"organization","name":"Summit Partners Growth Equity Fund IX-A, L.P.","position":2,"cik":"0001634415","reported_name":"Summit Partners Growth Equity Fund IX-A, L.P.","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":23869,"kind":"organization","name":"Summit Partners Growth Equity Fund IX-B, L.P.","position":3,"cik":"0001634426","reported_name":"Summit Partners Growth Equity Fund IX-B, L.P.","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":23870,"kind":"organization","name":"Summit Partners Co-Invest (Kiwi), LP","position":4,"cik":"0001830877","reported_name":"Summit Partners Co-Invest (Kiwi), LP","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":23871,"kind":"organization","name":"SUMMIT INVESTORS GE IX/VC IV, LLC","position":5,"cik":"0001654074","reported_name":"SUMMIT INVESTORS GE IX/VC IV, LLC","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":23872,"kind":"organization","name":"SUMMIT INVESTORS GE IX/VC IV (UK), L.P.","position":6,"cik":"0001846709","reported_name":"SUMMIT INVESTORS GE IX/VC IV (UK), L.P.","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}}],"security":"Series B Common Stock, par value $0.001 per share","published_at":"2026-08-13T20:30:07.000Z","date":"2026-08-11","kind":"exercise","planned":false,"acquired":true,"shares":5000000,"ownership":{"direct":false,"nature":"See footnotes"},"footnotes":[{"field":"derivative.exercise_price","element":"conversionOrExercisePrice","label":"F1","text":"The Series B common stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible into an equal number of shares of Series A common stock, par value $0.001 per share (\"Series A Common Stock\"), at any time, at the holder's election, and has no expiration date. Each share of Series B Common Stock will automatically convert into Series A Common Stock upon the earlier of (i) the date specified by 66-2/3% of the outstanding shares of Series B Common Stock, voting as a single series; (ii) following the seventh anniversary of the closing of Klaviyo, Inc.'s (the \"Company\") initial public offering; or (iii) any transfer, whether or not for value, except for certain permitted transfers described in the Company's certificate of incorporation."},{"field":"price","element":"transactionPricePerShare","label":"F1","text":"The Series B common stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible into an equal number of shares of Series A common stock, par value $0.001 per share (\"Series A Common Stock\"), at any time, at the holder's election, and has no expiration date. Each share of Series B Common Stock will automatically convert into Series A Common Stock upon the earlier of (i) the date specified by 66-2/3% of the outstanding shares of Series B Common Stock, voting as a single series; (ii) following the seventh anniversary of the closing of Klaviyo, Inc.'s (the \"Company\") initial public offering; or (iii) any transfer, whether or not for value, except for certain permitted transfers described in the Company's certificate of incorporation."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F1","text":"The Series B common stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible into an equal number of shares of Series A common stock, par value $0.001 per share (\"Series A Common Stock\"), at any time, at the holder's election, and has no expiration date. Each share of Series B Common Stock will automatically convert into Series A Common Stock upon the earlier of (i) the date specified by 66-2/3% of the outstanding shares of Series B Common Stock, voting as a single series; (ii) following the seventh anniversary of the closing of Klaviyo, Inc.'s (the \"Company\") initial public offering; or (iii) any transfer, whether or not for value, except for certain permitted transfers described in the Company's certificate of incorporation."},{"field":"derivative.expiration_date","element":"expirationDate","label":"F1","text":"The Series B common stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible into an equal number of shares of Series A common stock, par value $0.001 per share (\"Series A Common Stock\"), at any time, at the holder's election, and has no expiration date. Each share of Series B Common Stock will automatically convert into Series A Common Stock upon the earlier of (i) the date specified by 66-2/3% of the outstanding shares of Series B Common Stock, voting as a single series; (ii) following the seventh anniversary of the closing of Klaviyo, Inc.'s (the \"Company\") initial public offering; or (iii) any transfer, whether or not for value, except for certain permitted transfers described in the Company's certificate of incorporation."},{"field":"balance_after","element":"sharesOwnedFollowingTransaction","label":"F5","text":"Consists of (i) 8,187,302 shares of Series B Common Stock held by Fund IX-A, (ii) 5,112,037 shares of Series B Common Stock held by Fund IX-B, (iii) 504,825 shares of Series B Common Stock held by Kiwi Co-Invest Fund, (iv) 43,030 shares of Series B Common Stock held by Fund IX/VC IV, and (v) 5,584 shares of Series B Common Stock held by Fund IX/VC IV (UK)."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F2","text":"Summit Partners, L.P. is the manager of Summit Partners GE IX, LLC, which is the general partner of Summit Partners GE IX, LP, which is the general partner of Summit Partners Growth Equity Fund IX-A, L.P. (\"Fund IX-A\") and Summit Partners Growth Equity Fund IX-B, L.P. (\"Fund IX-B\"). Summit Partners, L.P. is the managing member of Summit Partners Co-Invest Kiwi GP, LLC, which is the general partner of Summit Partners Co-Invest (Kiwi), L.P. (\"Kiwi Co-Invest Fund\"). Summit Master Company, LLC is the general partner of Summit Partners, L.P., which is the manager of Summit Investors Management, LLC, which is the manager of Summit Investors GE IX/VC IV, LLC (\"Fund IX/VC IV\") and the general partner of Summit Investors GE IX/VC IV (UK), L.P. (\"Fund IX/VC IV (UK)\")."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F3","text":"(continued from footnote 2) Summit Master Company, LLC, as the managing member of Summit Investors Management, LLC, has delegated voting and investment decisions with respect to the securities held by Fund IX/VC IV and Fund IX/VC IV (UK) to Summit Partners, L.P."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F4","text":"The investment committee of Summit Partners, L.P., is currently composed of Peter Y. Chung, Scott C. Collins, and Peter L. Rottier, who may be deemed to have voting and dispositive authority over, and therefore beneficial ownership of, the reported securities. Each of the foregoing entities, Mr. Chung, Mr. Collins, and Mr. Rottier disclaims beneficial ownership of the shares, except to the extent of such person's or entity's pecuniary interest therein and the filing of this statement shall not be deemed an admission that any of the foregoing entities or persons are, for purposes of Section 16 of the Act or otherwise, the beneficial owner of any equity securities covered by this statement."}],"balance_after":13852778,"derivative":{"underlying":"Series A Common Stock, par value $0.001 per share","underlying_shares":5000000},"source":{"system":"sec-edgar","filing":"0001193125-26-349311","document":"ownership.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":3,"url":"https://www.sec.gov/Archives/edgar/data/830588/000119312526349311/ownership.xml","form_type":"4"}},{"id":688503,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":23867,"kind":"organization","name":"SUMMIT PARTNERS L P","position":1,"cik":"0000830588","reported_name":"SUMMIT PARTNERS L P","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":23868,"kind":"organization","name":"Summit Partners Growth Equity Fund IX-A, L.P.","position":2,"cik":"0001634415","reported_name":"Summit Partners Growth Equity Fund IX-A, L.P.","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":23869,"kind":"organization","name":"Summit Partners Growth Equity Fund IX-B, L.P.","position":3,"cik":"0001634426","reported_name":"Summit Partners Growth Equity Fund IX-B, L.P.","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":23870,"kind":"organization","name":"Summit Partners Co-Invest (Kiwi), LP","position":4,"cik":"0001830877","reported_name":"Summit Partners Co-Invest (Kiwi), LP","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":23871,"kind":"organization","name":"SUMMIT INVESTORS GE IX/VC IV, LLC","position":5,"cik":"0001654074","reported_name":"SUMMIT INVESTORS GE IX/VC IV, LLC","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":23872,"kind":"organization","name":"SUMMIT INVESTORS GE IX/VC IV (UK), L.P.","position":6,"cik":"0001846709","reported_name":"SUMMIT INVESTORS GE IX/VC IV (UK), L.P.","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}}],"security":"Series A Common Stock, par value $0.001 per share","published_at":"2026-08-13T20:30:07.000Z","date":"2026-08-11","kind":"sale","planned":false,"acquired":false,"shares":5000000,"price":17.71,"value":88550000.0,"ownership":{"direct":false,"nature":"See footnotes"},"footnotes":[{"field":"ownership.nature","element":"natureOfOwnership","label":"F2","text":"Summit Partners, L.P. is the manager of Summit Partners GE IX, LLC, which is the general partner of Summit Partners GE IX, LP, which is the general partner of Summit Partners Growth Equity Fund IX-A, L.P. (\"Fund IX-A\") and Summit Partners Growth Equity Fund IX-B, L.P. (\"Fund IX-B\"). Summit Partners, L.P. is the managing member of Summit Partners Co-Invest Kiwi GP, LLC, which is the general partner of Summit Partners Co-Invest (Kiwi), L.P. (\"Kiwi Co-Invest Fund\"). Summit Master Company, LLC is the general partner of Summit Partners, L.P., which is the manager of Summit Investors Management, LLC, which is the manager of Summit Investors GE IX/VC IV, LLC (\"Fund IX/VC IV\") and the general partner of Summit Investors GE IX/VC IV (UK), L.P. (\"Fund IX/VC IV (UK)\")."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F3","text":"(continued from footnote 2) Summit Master Company, LLC, as the managing member of Summit Investors Management, LLC, has delegated voting and investment decisions with respect to the securities held by Fund IX/VC IV and Fund IX/VC IV (UK) to Summit Partners, L.P."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F4","text":"The investment committee of Summit Partners, L.P., is currently composed of Peter Y. Chung, Scott C. Collins, and Peter L. Rottier, who may be deemed to have voting and dispositive authority over, and therefore beneficial ownership of, the reported securities. Each of the foregoing entities, Mr. Chung, Mr. Collins, and Mr. Rottier disclaims beneficial ownership of the shares, except to the extent of such person's or entity's pecuniary interest therein and the filing of this statement shall not be deemed an admission that any of the foregoing entities or persons are, for purposes of Section 16 of the Act or otherwise, the beneficial owner of any equity securities covered by this statement."}],"balance_after":0,"source":{"system":"sec-edgar","filing":"0001193125-26-349311","document":"ownership.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/830588/000119312526349311/ownership.xml","form_type":"4"}},{"id":688502,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":23867,"kind":"organization","name":"SUMMIT PARTNERS L P","position":1,"cik":"0000830588","reported_name":"SUMMIT PARTNERS L P","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":23868,"kind":"organization","name":"Summit Partners Growth Equity Fund IX-A, L.P.","position":2,"cik":"0001634415","reported_name":"Summit Partners Growth Equity Fund IX-A, L.P.","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":23869,"kind":"organization","name":"Summit Partners Growth Equity Fund IX-B, L.P.","position":3,"cik":"0001634426","reported_name":"Summit Partners Growth Equity Fund IX-B, L.P.","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":23870,"kind":"organization","name":"Summit Partners Co-Invest (Kiwi), LP","position":4,"cik":"0001830877","reported_name":"Summit Partners Co-Invest (Kiwi), LP","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":23871,"kind":"organization","name":"SUMMIT INVESTORS GE IX/VC IV, LLC","position":5,"cik":"0001654074","reported_name":"SUMMIT INVESTORS GE IX/VC IV, LLC","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":23872,"kind":"organization","name":"SUMMIT INVESTORS GE IX/VC IV (UK), L.P.","position":6,"cik":"0001846709","reported_name":"SUMMIT INVESTORS GE IX/VC IV (UK), L.P.","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}}],"security":"Series A Common Stock, par value $0.001 per share","published_at":"2026-08-13T20:30:07.000Z","date":"2026-08-11","kind":"exercise","planned":false,"acquired":true,"shares":5000000,"ownership":{"direct":false,"nature":"See footnotes"},"footnotes":[{"field":"price","element":"transactionPricePerShare","label":"F1","text":"The Series B common stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible into an equal number of shares of Series A common stock, par value $0.001 per share (\"Series A Common Stock\"), at any time, at the holder's election, and has no expiration date. Each share of Series B Common Stock will automatically convert into Series A Common Stock upon the earlier of (i) the date specified by 66-2/3% of the outstanding shares of Series B Common Stock, voting as a single series; (ii) following the seventh anniversary of the closing of Klaviyo, Inc.'s (the \"Company\") initial public offering; or (iii) any transfer, whether or not for value, except for certain permitted transfers described in the Company's certificate of incorporation."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F2","text":"Summit Partners, L.P. is the manager of Summit Partners GE IX, LLC, which is the general partner of Summit Partners GE IX, LP, which is the general partner of Summit Partners Growth Equity Fund IX-A, L.P. (\"Fund IX-A\") and Summit Partners Growth Equity Fund IX-B, L.P. (\"Fund IX-B\"). Summit Partners, L.P. is the managing member of Summit Partners Co-Invest Kiwi GP, LLC, which is the general partner of Summit Partners Co-Invest (Kiwi), L.P. (\"Kiwi Co-Invest Fund\"). Summit Master Company, LLC is the general partner of Summit Partners, L.P., which is the manager of Summit Investors Management, LLC, which is the manager of Summit Investors GE IX/VC IV, LLC (\"Fund IX/VC IV\") and the general partner of Summit Investors GE IX/VC IV (UK), L.P. (\"Fund IX/VC IV (UK)\")."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F3","text":"(continued from footnote 2) Summit Master Company, LLC, as the managing member of Summit Investors Management, LLC, has delegated voting and investment decisions with respect to the securities held by Fund IX/VC IV and Fund IX/VC IV (UK) to Summit Partners, L.P."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F4","text":"The investment committee of Summit Partners, L.P., is currently composed of Peter Y. Chung, Scott C. Collins, and Peter L. Rottier, who may be deemed to have voting and dispositive authority over, and therefore beneficial ownership of, the reported securities. Each of the foregoing entities, Mr. Chung, Mr. Collins, and Mr. Rottier disclaims beneficial ownership of the shares, except to the extent of such person's or entity's pecuniary interest therein and the filing of this statement shall not be deemed an admission that any of the foregoing entities or persons are, for purposes of Section 16 of the Act or otherwise, the beneficial owner of any equity securities covered by this statement."}],"balance_after":5000000,"source":{"system":"sec-edgar","filing":"0001193125-26-349311","document":"ownership.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/830588/000119312526349311/ownership.xml","form_type":"4"}},{"id":703394,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":14530,"kind":"person","name":"Oulman Roxanne","position":1,"cik":"0001523073","reported_name":"Oulman Roxanne","relationship":{"director":true,"officer":false,"ten_percent_owner":false,"other":false}}],"security":"Series B Common Stock","published_at":"2026-07-25T00:08:20.000Z","date":"2026-07-22","kind":"exercise","planned":false,"acquired":false,"shares":16775,"price":0,"value":0.0,"ownership":{"direct":false,"nature":"By Roxanne Oulman 2025 GRAT"},"footnotes":[{"field":"derivative.exercise_price","element":"conversionOrExercisePrice","label":"F1","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F1","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"derivative.expiration_date","element":"expirationDate","label":"F1","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F2","text":"Shares held by Roxanne Oulman 2025 GRAT, of which the Reporting Person serves as trustee. The Reporting Person disclaims Section 16 beneficial ownership of such shares except to the extent of her pecuniary interest therein, if any, and this report shall not be deemed to be an admission that she has beneficial ownership of such shares for Section 16 or any other purpose."}],"balance_after":29891,"derivative":{"underlying":"Series A Common Stock","underlying_shares":16775},"source":{"system":"sec-edgar","filing":"0001470831-26-000729","document":"wk-form4_1784938098.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":3,"url":"https://www.sec.gov/Archives/edgar/data/1523073/000147083126000729/wk-form4_1784938098.xml","form_type":"4"}},{"id":703393,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":14530,"kind":"person","name":"Oulman Roxanne","position":1,"cik":"0001523073","reported_name":"Oulman Roxanne","relationship":{"director":true,"officer":false,"ten_percent_owner":false,"other":false}}],"security":"Series A Common Stock","published_at":"2026-07-25T00:08:20.000Z","date":"2026-07-22","kind":"exercise","planned":false,"acquired":true,"shares":16775,"ownership":{"direct":false,"nature":"By Roxanne Oulman 2025 GRAT"},"footnotes":[{"field":"price","element":"transactionPricePerShare","label":"F1","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F2","text":"Shares held by Roxanne Oulman 2025 GRAT, of which the Reporting Person serves as trustee. The Reporting Person disclaims Section 16 beneficial ownership of such shares except to the extent of her pecuniary interest therein, if any, and this report shall not be deemed to be an admission that she has beneficial ownership of such shares for Section 16 or any other purpose."}],"balance_after":16775,"source":{"system":"sec-edgar","filing":"0001470831-26-000729","document":"wk-form4_1784938098.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1523073/000147083126000729/wk-form4_1784938098.xml","form_type":"4"}},{"id":706283,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":21993,"kind":"person","name":"Whalen Amanda","position":1,"cik":"0001991131","reported_name":"Whalen Amanda","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Chief Financial Officer"}}],"security":"Series A Common Stock","published_at":"2026-07-18T00:01:17.000Z","date":"2026-07-16","kind":"sale","planned":true,"acquired":false,"shares":14000,"price":17.75,"value":248500.0,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on August 21, 2025."},{"field":"price","element":"transactionPricePerShare","label":"F2","text":"The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $17.43 to $18.05 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."},{"field":"balance_after","element":"sharesOwnedFollowingTransaction","label":"F3","text":"Consists of (i) 59,302 shares of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"); (ii) 551,618 unvested restricted stock units awarded under the Issuer's 2023 Stock Option and Incentive Plan (the \"Plan\"), each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement; and (iii) 227,272 unvested performance stock units awarded under the Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement."}],"balance_after":838192,"source":{"system":"sec-edgar","filing":"0001470831-26-000720","document":"wk-form4_1784332874.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1835830/000147083126000720/wk-form4_1784332874.xml","form_type":"4"}},{"id":731527,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":21993,"kind":"person","name":"Whalen Amanda","position":1,"cik":"0001991131","reported_name":"Whalen Amanda","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Chief Financial Officer"}}],"security":"Series A Common Stock","published_at":"2026-06-19T00:08:45.000Z","date":"2026-06-18","kind":"sale","planned":true,"acquired":false,"shares":14000,"price":13.23,"value":185220.0,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on August 21, 2025."},{"field":"price","element":"transactionPricePerShare","label":"F2","text":"The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $13.12 to $13.49 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."},{"field":"balance_after","element":"sharesOwnedFollowingTransaction","label":"F3","text":"Consists of (i) 73,302 shares of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"); (ii) 551,618 unvested restricted stock units awarded under the Issuer's 2023 Stock Option and Incentive Plan (the \"Plan\"), each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement; and (iii) 227,272 unvested performance stock units awarded under the Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement."}],"balance_after":852192,"source":{"system":"sec-edgar","filing":"0001470831-26-000561","document":"wk-form4_1781827722.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1835830/000147083126000561/wk-form4_1781827722.xml","form_type":"4"}},{"id":741254,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":14530,"kind":"person","name":"Oulman Roxanne","position":1,"cik":"0001523073","reported_name":"Oulman Roxanne","relationship":{"director":true,"officer":false,"ten_percent_owner":false,"other":false}}],"security":"Series B Common Stock","published_at":"2026-06-12T00:04:22.000Z","date":"2026-06-11","kind":"exercise","planned":false,"acquired":false,"shares":8169,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"derivative.exercise_price","element":"conversionOrExercisePrice","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of Series A Common Stock of the Issuer, and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of Series A Common Stock of the Issuer, and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"derivative.expiration_date","element":"expirationDate","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of Series A Common Stock of the Issuer, and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."}],"balance_after":15165,"derivative":{"underlying":"Series A Common Stock","underlying_shares":8169},"source":{"system":"sec-edgar","filing":"0001470831-26-000542","document":"wk-form4_1781222659.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":3,"url":"https://www.sec.gov/Archives/edgar/data/1523073/000147083126000542/wk-form4_1781222659.xml","form_type":"4"}},{"id":741253,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":14530,"kind":"person","name":"Oulman Roxanne","position":1,"cik":"0001523073","reported_name":"Oulman Roxanne","relationship":{"director":true,"officer":false,"ten_percent_owner":false,"other":false}}],"security":"Series A Common Stock","published_at":"2026-06-12T00:04:22.000Z","date":"2026-06-11","kind":"exercise","planned":false,"acquired":true,"shares":8169,"ownership":{"direct":true},"footnotes":[{"field":"price","element":"transactionPricePerShare","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of Series A Common Stock of the Issuer, and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"balance_after","element":"sharesOwnedFollowingTransaction","label":"F3","text":"Consists of (i) 22,521 shares of Series A Common Stock and (ii) 14,822 unvested RSUs awarded under the Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement."}],"balance_after":37343,"source":{"system":"sec-edgar","filing":"0001470831-26-000542","document":"wk-form4_1781222659.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1523073/000147083126000542/wk-form4_1781222659.xml","form_type":"4"}},{"id":741252,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":14530,"kind":"person","name":"Oulman Roxanne","position":1,"cik":"0001523073","reported_name":"Oulman Roxanne","relationship":{"director":true,"officer":false,"ten_percent_owner":false,"other":false}}],"security":"Series A Common Stock","published_at":"2026-06-12T00:04:22.000Z","date":"2026-06-09","kind":"grant","planned":false,"acquired":true,"shares":14822,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"shares","element":"transactionShares","label":"F1","text":"Represents restricted stock units (\"RSUs\") awarded under the Issuer's 2023 Stock Option and Incentive Plan (the \"Plan\"), each representing the contingent right to receive one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), upon vesting and settlement. The RSUs vest in full upon the earlier of (i) June 9, 2027 or (ii) the date of the Issuer's next annual meeting of stockholders, in each case subject to the Reporting Person's continued service as a member of the Issuer's board of directors through such vesting date."}],"balance_after":29174,"source":{"system":"sec-edgar","filing":"0001470831-26-000542","document":"wk-form4_1781222659.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1523073/000147083126000542/wk-form4_1781222659.xml","form_type":"4"}},{"id":741697,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":39277,"kind":"person","name":"St. Ledger Susan","position":1,"cik":"0001673606","reported_name":"St. Ledger Susan","relationship":{"director":true,"officer":false,"ten_percent_owner":false,"other":false}}],"security":"Series A Common Stock","published_at":"2026-06-12T00:04:16.000Z","date":"2026-06-09","kind":"grant","planned":false,"acquired":true,"shares":14822,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"shares","element":"transactionShares","label":"F1","text":"Represents restricted stock units (\"RSUs\") awarded under the Issuer's 2023 Stock Option and Incentive Plan, each representing the contingent right to receive one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), upon vesting and settlement. The RSUs vest in full upon the earlier of (i) June 9, 2027 or (ii) the date of the Issuer's next annual meeting of stockholders, in each case subject to the Reporting Person's continued service as a member of the Issuer's board of directors through such vesting date."},{"field":"balance_after","element":"sharesOwnedFollowingTransaction","label":"F2","text":"Consists of (i) 10,939 shares of Series A Common Stock and (ii) 14,822 unvested RSUs awarded under the Issuer's 2023 Stock Option and Incentive Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement."}],"balance_after":25761,"source":{"system":"sec-edgar","filing":"0001470831-26-000541","document":"wk-form4_1781222653.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1673606/000147083126000541/wk-form4_1781222653.xml","form_type":"4"}},{"id":741685,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":39273,"kind":"person","name":"Ceran Jennifer","position":1,"cik":"0001652155","reported_name":"Ceran Jennifer","relationship":{"director":true,"officer":false,"ten_percent_owner":false,"other":false}}],"security":"Series A Common Stock","published_at":"2026-06-12T00:04:10.000Z","date":"2026-06-09","kind":"grant","planned":false,"acquired":true,"shares":14822,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"shares","element":"transactionShares","label":"F1","text":"Represents restricted stock units (\"RSUs\") awarded under the Issuer's 2023 Stock Option and Incentive Plan, each representing the contingent right to receive one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), upon vesting and settlement. The RSUs vest in full upon the earlier of (i) June 9, 2027 or (ii) the date of the Issuer's next annual meeting of stockholders, in each case subject to the Reporting Person's continued service as a member of the Issuer's board of directors through such vesting date."},{"field":"balance_after","element":"sharesOwnedFollowingTransaction","label":"F2","text":"Consists of (i) 30,691 shares of Series A Common Stock and (ii) 14,822 unvested RSUs awarded under the Issuer's 2023 Stock Option and Incentive Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement."}],"balance_after":45513,"source":{"system":"sec-edgar","filing":"0001470831-26-000540","document":"wk-form4_1781222647.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1652155/000147083126000540/wk-form4_1781222647.xml","form_type":"4"}},{"id":741733,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":37269,"kind":"person","name":"Weisman Tony","position":1,"cik":"0001716921","reported_name":"Weisman Tony","relationship":{"director":true,"officer":false,"ten_percent_owner":false,"other":false}}],"security":"Series A Common Stock","published_at":"2026-06-12T00:04:04.000Z","date":"2026-06-09","kind":"grant","planned":false,"acquired":true,"shares":14822,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"shares","element":"transactionShares","label":"F1","text":"Represents restricted stock units (\"RSUs\") awarded under the Issuer's 2023 Stock Option and Incentive Plan, each representing the contingent right to receive one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), upon vesting and settlement. The RSUs vest in full upon the earlier of (i) June 9, 2027 or (ii) the date of the Issuer's next annual meeting of stockholders, in each case subject to the Reporting Person's continued service as a member of the Issuer's board of directors through such vesting date."},{"field":"balance_after","element":"sharesOwnedFollowingTransaction","label":"F2","text":"Consists of (i) 89,352 shares of Series A Common Stock and (ii) 14,822 unvested RSUs awarded under the Issuer's 2023 Stock Option and Incentive Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement."}],"balance_after":104174,"source":{"system":"sec-edgar","filing":"0001470831-26-000539","document":"wk-form4_1781222642.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1716921/000147083126000539/wk-form4_1781222642.xml","form_type":"4"}},{"id":741740,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":22257,"kind":"person","name":"Fernandez Gomez Luciano","position":1,"cik":"0001730978","reported_name":"Fernandez Gomez Luciano","relationship":{"director":true,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Co-Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2026-06-12T00:03:58.000Z","date":"2026-06-09","kind":"tax_withholding","planned":false,"acquired":false,"shares":1746,"price":14.78,"value":25805.88,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"Represents shares of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), withheld by the Issuer to satisfy tax withholding obligations in connection with the vesting and settlement of restricted stock units (\"RSUs\")."},{"field":"balance_after","element":"sharesOwnedFollowingTransaction","label":"F2","text":"Consists of (i) 218,966 shares of Series A Common Stock; (ii) 911,501 unvested RSUs awarded under the Issuer's 2023 Stock Option and Incentive Plan (the \"Plan\"), each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement; and (iii) 1,193,238 unvested performance stock units awarded under the Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement."}],"balance_after":2323705,"source":{"system":"sec-edgar","filing":"0001470831-26-000538","document":"wk-form4_1781222635.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1730978/000147083126000538/wk-form4_1781222635.xml","form_type":"4"}},{"id":760418,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":43558,"kind":"person","name":"Bialecki Andrew","position":1,"cik":"0001991099","reported_name":"Bialecki Andrew","relationship":{"director":true,"officer":true,"ten_percent_owner":true,"other":false,"officer_title":"Co-Chief Executive Officer"}}],"security":"Series B Common Stock","published_at":"2026-05-29T00:08:04.000Z","date":"2026-05-26","kind":"exercise","planned":true,"acquired":false,"shares":212529,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"derivative.exercise_price","element":"conversionOrExercisePrice","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 20, 2025."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"derivative.expiration_date","element":"expirationDate","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."}],"balance_after":66731589,"derivative":{"underlying":"Series A Common Stock","underlying_shares":212529},"source":{"system":"sec-edgar","filing":"0001470831-26-000495","document":"wk-form4_1780013281.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":3,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000495/wk-form4_1780013281.xml","form_type":"4"}},{"id":760417,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":43558,"kind":"person","name":"Bialecki Andrew","position":1,"cik":"0001991099","reported_name":"Bialecki Andrew","relationship":{"director":true,"officer":true,"ten_percent_owner":true,"other":false,"officer_title":"Co-Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2026-05-29T00:08:04.000Z","date":"2026-05-26","kind":"sale","planned":true,"acquired":false,"shares":212529,"price":14.61,"value":3105048.69,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 20, 2025."},{"field":"price","element":"transactionPricePerShare","label":"F3","text":"The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $14.43 to $15.00 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."}],"balance_after":0,"source":{"system":"sec-edgar","filing":"0001470831-26-000495","document":"wk-form4_1780013281.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000495/wk-form4_1780013281.xml","form_type":"4"}},{"id":760416,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":43558,"kind":"person","name":"Bialecki Andrew","position":1,"cik":"0001991099","reported_name":"Bialecki Andrew","relationship":{"director":true,"officer":true,"ten_percent_owner":true,"other":false,"officer_title":"Co-Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2026-05-29T00:08:04.000Z","date":"2026-05-26","kind":"exercise","planned":true,"acquired":true,"shares":212529,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 20, 2025."},{"field":"price","element":"transactionPricePerShare","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."}],"balance_after":212529,"source":{"system":"sec-edgar","filing":"0001470831-26-000495","document":"wk-form4_1780013281.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000495/wk-form4_1780013281.xml","form_type":"4"}},{"id":770025,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":39277,"kind":"person","name":"St. Ledger Susan","position":1,"cik":"0001673606","reported_name":"St. Ledger Susan","relationship":{"director":true,"officer":false,"ten_percent_owner":false,"other":false}}],"security":"Series B Common Stock","published_at":"2026-05-21T00:05:43.000Z","date":"2026-05-18","kind":"exercise","planned":true,"acquired":false,"shares":9334,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"derivative.exercise_price","element":"conversionOrExercisePrice","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on June 11, 2025."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"derivative.expiration_date","element":"expirationDate","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"balance_after","element":"sharesOwnedFollowingTransaction","label":"F4","text":"Consists of 50,166 shares of Series B Common Stock."}],"balance_after":50166,"derivative":{"underlying":"Series A Common Stock","underlying_shares":9334},"source":{"system":"sec-edgar","filing":"0001470831-26-000481","document":"wk-form4_1779321940.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":3,"url":"https://www.sec.gov/Archives/edgar/data/1673606/000147083126000481/wk-form4_1779321940.xml","form_type":"4"}},{"id":770024,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":39277,"kind":"person","name":"St. Ledger Susan","position":1,"cik":"0001673606","reported_name":"St. Ledger Susan","relationship":{"director":true,"officer":false,"ten_percent_owner":false,"other":false}}],"security":"Series A Common Stock","published_at":"2026-05-21T00:05:43.000Z","date":"2026-05-18","kind":"sale","planned":true,"acquired":false,"shares":9334,"price":14.27,"value":133196.18,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on June 11, 2025."},{"field":"balance_after","element":"sharesOwnedFollowingTransaction","label":"F3","text":"Consists of (i) 5,119 shares of Series A Common Stock and (ii) 5,820 unvested restricted stock units awarded under the Issuer's 2023 Stock Option and Incentive Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement."}],"balance_after":10939,"source":{"system":"sec-edgar","filing":"0001470831-26-000481","document":"wk-form4_1779321940.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1673606/000147083126000481/wk-form4_1779321940.xml","form_type":"4"}},{"id":770023,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":39277,"kind":"person","name":"St. Ledger Susan","position":1,"cik":"0001673606","reported_name":"St. Ledger Susan","relationship":{"director":true,"officer":false,"ten_percent_owner":false,"other":false}}],"security":"Series A Common Stock","published_at":"2026-05-21T00:05:43.000Z","date":"2026-05-18","kind":"exercise","planned":true,"acquired":true,"shares":9334,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on June 11, 2025."},{"field":"price","element":"transactionPricePerShare","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."}],"balance_after":20273,"source":{"system":"sec-edgar","filing":"0001470831-26-000481","document":"wk-form4_1779321940.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1673606/000147083126000481/wk-form4_1779321940.xml","form_type":"4"}},{"id":770232,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":43558,"kind":"person","name":"Bialecki Andrew","position":1,"cik":"0001991099","reported_name":"Bialecki Andrew","relationship":{"director":true,"officer":true,"ten_percent_owner":true,"other":false,"officer_title":"Co-Chief Executive Officer"}}],"security":"Series B Common Stock","published_at":"2026-05-21T00:03:53.000Z","date":"2026-05-19","kind":"exercise","planned":true,"acquired":false,"shares":200000,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"derivative.exercise_price","element":"conversionOrExercisePrice","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 20, 2025."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"derivative.expiration_date","element":"expirationDate","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."}],"balance_after":66944118,"derivative":{"underlying":"Series A Common Stock","underlying_shares":200000},"source":{"system":"sec-edgar","filing":"0001470831-26-000479","document":"wk-form4_1779321830.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":3,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000479/wk-form4_1779321830.xml","form_type":"4"}},{"id":770231,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":43558,"kind":"person","name":"Bialecki Andrew","position":1,"cik":"0001991099","reported_name":"Bialecki Andrew","relationship":{"director":true,"officer":true,"ten_percent_owner":true,"other":false,"officer_title":"Co-Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2026-05-21T00:03:53.000Z","date":"2026-05-19","kind":"sale","planned":true,"acquired":false,"shares":200000,"price":14.88,"value":2976000.0,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 20, 2025."},{"field":"price","element":"transactionPricePerShare","label":"F3","text":"The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $14.68 to $15.41 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."}],"balance_after":0,"source":{"system":"sec-edgar","filing":"0001470831-26-000479","document":"wk-form4_1779321830.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000479/wk-form4_1779321830.xml","form_type":"4"}},{"id":770230,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":43558,"kind":"person","name":"Bialecki Andrew","position":1,"cik":"0001991099","reported_name":"Bialecki Andrew","relationship":{"director":true,"officer":true,"ten_percent_owner":true,"other":false,"officer_title":"Co-Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2026-05-21T00:03:53.000Z","date":"2026-05-19","kind":"exercise","planned":true,"acquired":true,"shares":200000,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 20, 2025."},{"field":"price","element":"transactionPricePerShare","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."}],"balance_after":200000,"source":{"system":"sec-edgar","filing":"0001470831-26-000479","document":"wk-form4_1779321830.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000479/wk-form4_1779321830.xml","form_type":"4"}},{"id":775358,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":18020,"kind":"person","name":"Edmond Landon","position":1,"cik":"0001991399","reported_name":"Edmond Landon","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Chief Legal Officer"}}],"security":"Series A Common Stock","published_at":"2026-05-19T00:16:06.000Z","date":"2026-05-15","kind":"tax_withholding","planned":false,"acquired":false,"shares":22340,"price":14.38,"value":321249.2,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"Represents shares of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), withheld by the Issuer to satisfy tax withholding obligations in connection with the vesting and settlement of restricted stock units (\"RSUs\")."},{"field":"balance_after","element":"sharesOwnedFollowingTransaction","label":"F2","text":"Consists of (i) 93,396 shares of Series A Common Stock; (ii) 338,518 unvested RSUs awarded under the Issuer's 2023 Stock Option and Incentive Plan (the \"Plan\"), each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement; and (iii) 129,870 unvested performance stock units awarded under the Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement."}],"balance_after":561784,"source":{"system":"sec-edgar","filing":"0001470831-26-000461","document":"wk-form4_1779149764.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1991399/000147083126000461/wk-form4_1779149764.xml","form_type":"4"}},{"id":775099,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":22257,"kind":"person","name":"Fernandez Gomez Luciano","position":1,"cik":"0001730978","reported_name":"Fernandez Gomez Luciano","relationship":{"director":true,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Co-Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2026-05-19T00:14:32.000Z","date":"2026-05-15","kind":"tax_withholding","planned":false,"acquired":false,"shares":22132,"price":14.38,"value":318258.16,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"Represents shares of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), withheld by the Issuer to satisfy tax withholding obligations in connection with the vesting and settlement of restricted stock units (\"RSUs\")."},{"field":"balance_after","element":"sharesOwnedFollowingTransaction","label":"F2","text":"Consists of (i) 214,892 shares of Series A Common Stock; (ii) 917,321 unvested RSUs awarded under the Issuer's 2023 Stock Option and Incentive Plan (the \"Plan\"), each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement; and (iii) 1,193,238 unvested performance stock units awarded under the Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement."}],"balance_after":2325451,"source":{"system":"sec-edgar","filing":"0001470831-26-000459","document":"wk-form4_1779149670.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1730978/000147083126000459/wk-form4_1779149670.xml","form_type":"4"}},{"id":775100,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":22259,"kind":"person","name":"Galvin Carmel","position":1,"cik":"0001733091","reported_name":"Galvin Carmel","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Chief People Officer"}}],"security":"Series A Common Stock","published_at":"2026-05-19T00:11:55.000Z","date":"2026-05-15","kind":"tax_withholding","planned":false,"acquired":false,"shares":30541,"price":14.38,"value":439179.58,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"Represents shares of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), withheld by the Issuer to satisfy tax withholding obligations in connection with the vesting and settlement of restricted stock units (\"RSUs\")."},{"field":"balance_after","element":"sharesOwnedFollowingTransaction","label":"F2","text":"Consists of (i) 163,109 shares of Series A Common Stock; (ii) 612,553 unvested RSUs awarded under the Issuer's 2023 Stock Option and Incentive Plan (the \"Plan\"), each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement; and (iii) 162,337 unvested performance stock units awarded under the Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement."}],"balance_after":937999,"source":{"system":"sec-edgar","filing":"0001470831-26-000457","document":"wk-form4_1779149513.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1733091/000147083126000457/wk-form4_1779149513.xml","form_type":"4"}},{"id":774231,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":21993,"kind":"person","name":"Whalen Amanda","position":1,"cik":"0001991131","reported_name":"Whalen Amanda","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Chief Financial Officer"}}],"security":"Series B Common Stock","published_at":"2026-05-19T00:08:41.000Z","date":"2026-05-15","kind":"exercise","planned":true,"acquired":false,"shares":13527,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"derivative.exercise_price","element":"conversionOrExercisePrice","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"kind","element":"transactionCoding","label":"F4","text":"Represents 13,527 shares of Series B Common Stock automatically converted into shares of Series A Common Stock in connection with tax withholding obligations related to the vesting and settlement of restricted stock units (\"RSUs\")."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"derivative.expiration_date","element":"expirationDate","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"balance_after","element":"sharesOwnedFollowingTransaction","label":"F7","text":"Consists of 269,585 shares of Series B Common Stock."}],"balance_after":269585,"derivative":{"underlying":"Series A Common Stock","underlying_shares":13527},"source":{"system":"sec-edgar","filing":"0001470831-26-000455","document":"wk-form4_1779149319.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":6,"url":"https://www.sec.gov/Archives/edgar/data/1835830/000147083126000455/wk-form4_1779149319.xml","form_type":"4"}},{"id":774230,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":21993,"kind":"person","name":"Whalen Amanda","position":1,"cik":"0001991131","reported_name":"Whalen Amanda","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Chief Financial Officer"}}],"security":"Series B Common Stock","published_at":"2026-05-19T00:08:41.000Z","date":"2026-05-14","kind":"exercise","planned":true,"acquired":false,"shares":14000,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"derivative.exercise_price","element":"conversionOrExercisePrice","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on August 21, 2025."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"derivative.expiration_date","element":"expirationDate","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."}],"balance_after":283112,"derivative":{"underlying":"Series A Common Stock","underlying_shares":14000},"source":{"system":"sec-edgar","filing":"0001470831-26-000455","document":"wk-form4_1779149319.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":5,"url":"https://www.sec.gov/Archives/edgar/data/1835830/000147083126000455/wk-form4_1779149319.xml","form_type":"4"}},{"id":774229,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":21993,"kind":"person","name":"Whalen Amanda","position":1,"cik":"0001991131","reported_name":"Whalen Amanda","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Chief Financial Officer"}}],"security":"Series A Common Stock","published_at":"2026-05-19T00:08:41.000Z","date":"2026-05-15","kind":"tax_withholding","planned":true,"acquired":false,"shares":42476,"price":14.38,"value":610804.88,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F5","text":"Represents shares of Series A Common Stock withheld by the Issuer to satisfy tax withholding obligations in connection with the vesting and settlement of RSUs."},{"field":"balance_after","element":"sharesOwnedFollowingTransaction","label":"F6","text":"Consists of (i) 87,302 shares of Series A Common Stock; (ii) 551,618 unvested RSUs awarded under the Issuer's 2023 Stock Option and Incentive Plan (the \"Plan\"), each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement; and (iii) 227,272 unvested performance stock units awarded under the Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement."}],"balance_after":866192,"source":{"system":"sec-edgar","filing":"0001470831-26-000455","document":"wk-form4_1779149319.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":4,"url":"https://www.sec.gov/Archives/edgar/data/1835830/000147083126000455/wk-form4_1779149319.xml","form_type":"4"}},{"id":774228,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":21993,"kind":"person","name":"Whalen Amanda","position":1,"cik":"0001991131","reported_name":"Whalen Amanda","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Chief Financial Officer"}}],"security":"Series A Common Stock","published_at":"2026-05-19T00:08:41.000Z","date":"2026-05-15","kind":"exercise","planned":true,"acquired":true,"shares":13527,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F4","text":"Represents 13,527 shares of Series B Common Stock automatically converted into shares of Series A Common Stock in connection with tax withholding obligations related to the vesting and settlement of restricted stock units (\"RSUs\")."},{"field":"price","element":"transactionPricePerShare","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."}],"balance_after":908668,"source":{"system":"sec-edgar","filing":"0001470831-26-000455","document":"wk-form4_1779149319.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":3,"url":"https://www.sec.gov/Archives/edgar/data/1835830/000147083126000455/wk-form4_1779149319.xml","form_type":"4"}},{"id":774227,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":21993,"kind":"person","name":"Whalen Amanda","position":1,"cik":"0001991131","reported_name":"Whalen Amanda","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Chief Financial Officer"}}],"security":"Series A Common Stock","published_at":"2026-05-19T00:08:41.000Z","date":"2026-05-14","kind":"sale","planned":true,"acquired":false,"shares":14000,"price":14.26,"value":199640.0,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on August 21, 2025."},{"field":"price","element":"transactionPricePerShare","label":"F3","text":"The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $13.88 to $14.45 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."}],"balance_after":895141,"source":{"system":"sec-edgar","filing":"0001470831-26-000455","document":"wk-form4_1779149319.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1835830/000147083126000455/wk-form4_1779149319.xml","form_type":"4"}},{"id":774226,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":21993,"kind":"person","name":"Whalen Amanda","position":1,"cik":"0001991131","reported_name":"Whalen Amanda","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Chief Financial Officer"}}],"security":"Series A Common Stock","published_at":"2026-05-19T00:08:41.000Z","date":"2026-05-14","kind":"exercise","planned":true,"acquired":true,"shares":14000,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on August 21, 2025."},{"field":"price","element":"transactionPricePerShare","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."}],"balance_after":909141,"source":{"system":"sec-edgar","filing":"0001470831-26-000455","document":"wk-form4_1779149319.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1835830/000147083126000455/wk-form4_1779149319.xml","form_type":"4"}},{"id":779460,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":43558,"kind":"person","name":"Bialecki Andrew","position":1,"cik":"0001991099","reported_name":"Bialecki Andrew","relationship":{"director":true,"officer":true,"ten_percent_owner":true,"other":false,"officer_title":"Co-Chief Executive Officer"}}],"security":"Series B Common Stock","published_at":"2026-05-15T00:06:07.000Z","date":"2026-05-12","kind":"exercise","planned":true,"acquired":false,"shares":200000,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"derivative.exercise_price","element":"conversionOrExercisePrice","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 20, 2025."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"derivative.expiration_date","element":"expirationDate","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."}],"balance_after":67144118,"derivative":{"underlying":"Series A Common Stock","underlying_shares":200000},"source":{"system":"sec-edgar","filing":"0001470831-26-000440","document":"wk-form4_1778803561.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":4,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000440/wk-form4_1778803561.xml","form_type":"4"}},{"id":779459,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":43558,"kind":"person","name":"Bialecki Andrew","position":1,"cik":"0001991099","reported_name":"Bialecki Andrew","relationship":{"director":true,"officer":true,"ten_percent_owner":true,"other":false,"officer_title":"Co-Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2026-05-15T00:06:07.000Z","date":"2026-05-12","kind":"sale","planned":true,"acquired":false,"shares":141316,"price":14.46,"value":2043429.36,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 20, 2025."},{"field":"price","element":"transactionPricePerShare","label":"F4","text":"The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $14.30 to $14.73 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."}],"balance_after":0,"source":{"system":"sec-edgar","filing":"0001470831-26-000440","document":"wk-form4_1778803561.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":3,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000440/wk-form4_1778803561.xml","form_type":"4"}},{"id":779458,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":43558,"kind":"person","name":"Bialecki Andrew","position":1,"cik":"0001991099","reported_name":"Bialecki Andrew","relationship":{"director":true,"officer":true,"ten_percent_owner":true,"other":false,"officer_title":"Co-Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2026-05-15T00:06:07.000Z","date":"2026-05-12","kind":"sale","planned":true,"acquired":false,"shares":58684,"price":14.97,"value":878499.48,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 20, 2025."},{"field":"price","element":"transactionPricePerShare","label":"F3","text":"The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $14.74 to $15.73 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."}],"balance_after":141316,"source":{"system":"sec-edgar","filing":"0001470831-26-000440","document":"wk-form4_1778803561.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000440/wk-form4_1778803561.xml","form_type":"4"}},{"id":779457,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":43558,"kind":"person","name":"Bialecki Andrew","position":1,"cik":"0001991099","reported_name":"Bialecki Andrew","relationship":{"director":true,"officer":true,"ten_percent_owner":true,"other":false,"officer_title":"Co-Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2026-05-15T00:06:07.000Z","date":"2026-05-12","kind":"exercise","planned":true,"acquired":true,"shares":200000,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 20, 2025."},{"field":"price","element":"transactionPricePerShare","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."}],"balance_after":200000,"source":{"system":"sec-edgar","filing":"0001470831-26-000440","document":"wk-form4_1778803561.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000440/wk-form4_1778803561.xml","form_type":"4"}},{"id":797838,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":18319,"kind":"organization","name":"Shopify Strategic Holdings 3 LLC","position":1,"cik":"0001993562","reported_name":"Shopify Strategic Holdings 3 LLC","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":2851,"kind":"organization","name":"SHOPIFY INC.","position":2,"cik":"0001594805","reported_name":"SHOPIFY INC.","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}}],"security":"Series B Common Stock","published_at":"2026-04-29T20:30:06.000Z","date":"2026-04-28","kind":"other","planned":false,"acquired":true,"shares":344381,"price":0.01,"value":3443.81,"ownership":{"direct":true},"footnotes":[{"field":"derivative.exercise_price","element":"conversionOrExercisePrice","label":"F3","text":"Each share of Series B Common Stock is convertible at any time at the option of the holder into one share of Series A Common Stock of the Issuer, and will automatically convert into Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F3","text":"Each share of Series B Common Stock is convertible at any time at the option of the holder into one share of Series A Common Stock of the Issuer, and will automatically convert into Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"derivative.expiration_date","element":"expirationDate","label":"F3","text":"Each share of Series B Common Stock is convertible at any time at the option of the holder into one share of Series A Common Stock of the Issuer, and will automatically convert into Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"ownership.direct","element":"directOrIndirectOwnership","label":"F2","text":"Reflects securities held directly by Shopify Strategic Holdings 3 LLC, a wholly-owned subsidiary of Shopify Inc. (\"Shopify\"). Shopify is an indirect beneficial owner and disclaims beneficial ownership except to the extent of its pecuniary interest therein."}],"balance_after":16973108,"derivative":{"underlying":"Series A Common Stock","underlying_shares":344381},"source":{"system":"sec-edgar","filing":"0001193125-26-191903","document":"ownership.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1594805/000119312526191903/ownership.xml","form_type":"4"}},{"id":797837,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":18319,"kind":"organization","name":"Shopify Strategic Holdings 3 LLC","position":1,"cik":"0001993562","reported_name":"Shopify Strategic Holdings 3 LLC","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":2851,"kind":"organization","name":"SHOPIFY INC.","position":2,"cik":"0001594805","reported_name":"SHOPIFY INC.","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}}],"security":"Warrants to Purchase Series B Common Stock (Right to Buy)","published_at":"2026-04-29T20:30:06.000Z","date":"2026-04-28","kind":"other","planned":false,"acquired":false,"shares":344381,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"derivative.exercise_date","element":"exerciseDate","label":"F1","text":"25% of the shares subject to the warrants vested on July 28, 2022, and the remaining shares vest quarterly in equal amounts through July 28, 2027. Notwithstanding the foregoing, in connection with the Issuer's initial public offering (\"IPO\"), 25% of the total number of shares subject to the warrants vested immediately prior to the completion of the IPO."},{"field":"ownership.direct","element":"directOrIndirectOwnership","label":"F2","text":"Reflects securities held directly by Shopify Strategic Holdings 3 LLC, a wholly-owned subsidiary of Shopify Inc. (\"Shopify\"). Shopify is an indirect beneficial owner and disclaims beneficial ownership except to the extent of its pecuniary interest therein."}],"balance_after":1721912,"derivative":{"exercise_price":0.01,"expiration_date":"2032-07-28","underlying":"Series B Common Stock","underlying_shares":344381},"source":{"system":"sec-edgar","filing":"0001193125-26-191903","document":"ownership.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1594805/000119312526191903/ownership.xml","form_type":"4"}},{"id":803010,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":18020,"kind":"person","name":"Edmond Landon","position":1,"cik":"0001991399","reported_name":"Edmond Landon","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Chief Legal Officer"}}],"security":"Series A Common Stock","published_at":"2026-04-23T00:01:18.000Z","date":"2026-04-20","kind":"sale","planned":true,"acquired":false,"shares":9623,"price":20,"value":192460.0,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on August 21, 2025."},{"field":"balance_after","element":"sharesOwnedFollowingTransaction","label":"F2","text":"Consists of (i) 74,332 shares of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), (ii) 379,922 unvested restricted stock units awarded under the Issuer's 2023 Stock Option and Incentive Plan (the \"Plan\"), each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement, and (iii) 129,870 unvested performance stock units awarded under the Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement."}],"balance_after":584124,"source":{"system":"sec-edgar","filing":"0001470831-26-000400","document":"wk-form4_1776902476.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1991399/000147083126000400/wk-form4_1776902476.xml","form_type":"4"}},{"id":805844,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":18020,"kind":"person","name":"Edmond Landon","position":1,"cik":"0001991399","reported_name":"Edmond Landon","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Chief Legal Officer"}}],"security":"Series A Common Stock","published_at":"2026-04-18T00:14:40.000Z","date":"2026-04-15","kind":"grant","planned":false,"acquired":true,"shares":129870,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"shares","element":"transactionShares","label":"F2","text":"Represents performance stock units (\"PSUs\") awarded under the Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement. The PSUs will vest in up to three tranches over a two-year measurement period, subject to the achievement of specified performance targets tied to the trading price of the Series A Common Stock and the Reporting Person's continued service in the same or substantially equivalent position as the Reporting Person held as of the grant date through the applicable vesting date. Each tranche of PSUs will vest only if the average closing price of the Series A Common Stock for a period of at least sixty consecutive calendar days is at or above a specified dollar value during the applicable measurement period."},{"field":"shares","element":"transactionShares","label":"F3","text":"(continued) The stock price targets for tranches 1 through 3 are $30.00, $50.00, and $75.00 per share, respectively, subject to proportionate adjustment in the event of any stock split or other similar change in the Issuer's capital stock."},{"field":"balance_after","element":"sharesOwnedFollowingTransaction","label":"F4","text":"Consists of (i) 83,955 shares of Series A Common Stock; (ii) 379,922 unvested RSUs awarded under the Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement; and (iii) 129,870 unvested PSUs awarded under the Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement."}],"balance_after":593747,"source":{"system":"sec-edgar","filing":"0001470831-26-000384","document":"wk-form4_1776471278.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1991399/000147083126000384/wk-form4_1776471278.xml","form_type":"4"}},{"id":805843,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":18020,"kind":"person","name":"Edmond Landon","position":1,"cik":"0001991399","reported_name":"Edmond Landon","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Chief Legal Officer"}}],"security":"Series A Common Stock","published_at":"2026-04-18T00:14:40.000Z","date":"2026-04-15","kind":"grant","planned":false,"acquired":true,"shares":151515,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"shares","element":"transactionShares","label":"F1","text":"Represents restricted stock units (\"RSUs\") awarded under the Issuer's 2023 Stock Option and Incentive Plan (the \"Plan\"), each representing the contingent right to receive one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), upon vesting and settlement. The RSUs vest as follows: (i) 50% of the RSUs will vest in eight equal quarterly installments, with the first such installment vesting on May 15, 2026, and (ii) thereafter the remaining 50% of the RSUs will vest in four equal quarterly installments, subject to the Reporting Person's continued service on each such vesting date."}],"balance_after":463877,"source":{"system":"sec-edgar","filing":"0001470831-26-000384","document":"wk-form4_1776471278.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1991399/000147083126000384/wk-form4_1776471278.xml","form_type":"4"}},{"id":805664,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":22259,"kind":"person","name":"Galvin Carmel","position":1,"cik":"0001733091","reported_name":"Galvin Carmel","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Chief People Officer"}}],"security":"Series A Common Stock","published_at":"2026-04-18T00:13:11.000Z","date":"2026-04-15","kind":"grant","planned":false,"acquired":true,"shares":162337,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"shares","element":"transactionShares","label":"F2","text":"Represents performance stock units (\"PSUs\") awarded under the Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement. The PSUs will vest in up to three tranches over a two-year measurement period, subject to the achievement of specified performance targets tied to the trading price of the Series A Common Stock and the Reporting Person's continued service in the same or substantially equivalent position as the Reporting Person held as of the grant date through the applicable vesting date. Each tranche of PSUs will vest only if the average closing price of the Series A Common Stock for a period of at least sixty consecutive calendar days is at or above a specified dollar value during the applicable measurement period."},{"field":"shares","element":"transactionShares","label":"F3","text":"(continued) The stock price targets for tranches 1 through 3 are $30.00, $50.00, and $75.00 per share, respectively, subject to proportionate adjustment in the event of any stock split or other similar change in the Issuer's capital stock."},{"field":"balance_after","element":"sharesOwnedFollowingTransaction","label":"F4","text":"Consists of (i) 130,487 shares of Series A Common Stock; (ii) 675,716 unvested RSUs awarded under the Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement; and (iii) 162,337 unvested PSUs awarded under the Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement."}],"balance_after":968540,"source":{"system":"sec-edgar","filing":"0001470831-26-000382","document":"wk-form4_1776471189.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1733091/000147083126000382/wk-form4_1776471189.xml","form_type":"4"}},{"id":805663,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":22259,"kind":"person","name":"Galvin Carmel","position":1,"cik":"0001733091","reported_name":"Galvin Carmel","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Chief People Officer"}}],"security":"Series A Common Stock","published_at":"2026-04-18T00:13:11.000Z","date":"2026-04-15","kind":"grant","planned":false,"acquired":true,"shares":189393,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"shares","element":"transactionShares","label":"F1","text":"Represents restricted stock units (\"RSUs\") awarded under the Issuer's 2023 Stock Option and Incentive Plan (the \"Plan\"), each representing the contingent right to receive one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), upon vesting and settlement. The RSUs vest as follows: (i) 50% of the RSUs will vest in eight equal quarterly installments, with the first such installment vesting on May 15, 2026, and (ii) thereafter the remaining 50% of the RSUs will vest in four equal quarterly installments, subject to the Reporting Person's continued service on each such vesting date."}],"balance_after":806203,"source":{"system":"sec-edgar","filing":"0001470831-26-000382","document":"wk-form4_1776471189.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1733091/000147083126000382/wk-form4_1776471189.xml","form_type":"4"}},{"id":805000,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":21993,"kind":"person","name":"Whalen Amanda","position":1,"cik":"0001991131","reported_name":"Whalen Amanda","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Chief Financial Officer"}}],"security":"Series B Common Stock","published_at":"2026-04-18T00:10:58.000Z","date":"2026-04-16","kind":"exercise","planned":true,"acquired":false,"shares":4293,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"derivative.exercise_price","element":"conversionOrExercisePrice","label":"F5","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of Series A Common Stock, and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"kind","element":"transactionCoding","label":"F4","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on August 21, 2025."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F5","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of Series A Common Stock, and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"derivative.expiration_date","element":"expirationDate","label":"F5","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of Series A Common Stock, and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"balance_after","element":"sharesOwnedFollowingTransaction","label":"F8","text":"Consists of (i) 262,737 shares of Series B Common Stock and (ii) 34,375 unvested RSUs awarded under the Issuer's 2015 Stock Incentive Plan, each representing the contingent right to receive one share of Series B Common Stock upon vesting and settlement."}],"balance_after":297112,"derivative":{"underlying":"Series A Common Stock","underlying_shares":4293},"source":{"system":"sec-edgar","filing":"0001470831-26-000380","document":"wk-form4_1776471055.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":5,"url":"https://www.sec.gov/Archives/edgar/data/1835830/000147083126000380/wk-form4_1776471055.xml","form_type":"4"}},{"id":804999,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":21993,"kind":"person","name":"Whalen Amanda","position":1,"cik":"0001991131","reported_name":"Whalen Amanda","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Chief Financial Officer"}}],"security":"Series A Common Stock","published_at":"2026-04-18T00:10:58.000Z","date":"2026-04-16","kind":"sale","planned":true,"acquired":false,"shares":14000,"price":18.54,"value":259560.0,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F4","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on August 21, 2025."},{"field":"price","element":"transactionPricePerShare","label":"F6","text":"The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $18.34 to $18.98 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."},{"field":"balance_after","element":"sharesOwnedFollowingTransaction","label":"F7","text":"Consists of (i) 42,687 shares of Series A Common Stock; (ii) 625,182 unvested RSUs awarded under the Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement; and (iii) 227,272 unvested PSUs awarded under the Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement."}],"balance_after":895141,"source":{"system":"sec-edgar","filing":"0001470831-26-000380","document":"wk-form4_1776471055.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":4,"url":"https://www.sec.gov/Archives/edgar/data/1835830/000147083126000380/wk-form4_1776471055.xml","form_type":"4"}},{"id":804998,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":21993,"kind":"person","name":"Whalen Amanda","position":1,"cik":"0001991131","reported_name":"Whalen Amanda","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Chief Financial Officer"}}],"security":"Series A Common Stock","published_at":"2026-04-18T00:10:58.000Z","date":"2026-04-16","kind":"exercise","planned":true,"acquired":true,"shares":4293,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F4","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on August 21, 2025."},{"field":"price","element":"transactionPricePerShare","label":"F5","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of Series A Common Stock, and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."}],"balance_after":909141,"source":{"system":"sec-edgar","filing":"0001470831-26-000380","document":"wk-form4_1776471055.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":3,"url":"https://www.sec.gov/Archives/edgar/data/1835830/000147083126000380/wk-form4_1776471055.xml","form_type":"4"}},{"id":804997,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":21993,"kind":"person","name":"Whalen Amanda","position":1,"cik":"0001991131","reported_name":"Whalen Amanda","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Chief Financial Officer"}}],"security":"Series A Common Stock","published_at":"2026-04-18T00:10:58.000Z","date":"2026-04-15","kind":"grant","planned":true,"acquired":true,"shares":227272,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"shares","element":"transactionShares","label":"F2","text":"Represents performance stock units (\"PSUs\") awarded under the Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement. The PSUs will vest in up to three tranches over a two-year measurement period, subject to the achievement of specified performance targets tied to the trading price of the Series A Common Stock and the Reporting Person's continued service in the same or substantially equivalent position as the Reporting Person held as of the grant date through the applicable vesting date. Each tranche of PSUs will vest only if the average closing price of the Series A Common Stock for a period of at least sixty consecutive calendar days is at or above a specified dollar value during the applicable measurement period."},{"field":"shares","element":"transactionShares","label":"F3","text":"(continued) The stock price targets for tranches 1 through 3 are $30.00, $50.00, and $75.00 per share, respectively, subject to proportionate adjustment in the event of any stock split or other similar change in the Issuer's capital stock."}],"balance_after":904848,"source":{"system":"sec-edgar","filing":"0001470831-26-000380","document":"wk-form4_1776471055.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1835830/000147083126000380/wk-form4_1776471055.xml","form_type":"4"}},{"id":804996,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":21993,"kind":"person","name":"Whalen Amanda","position":1,"cik":"0001991131","reported_name":"Whalen Amanda","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Chief Financial Officer"}}],"security":"Series A Common Stock","published_at":"2026-04-18T00:10:58.000Z","date":"2026-04-15","kind":"grant","planned":true,"acquired":true,"shares":265151,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"shares","element":"transactionShares","label":"F1","text":"Represents restricted stock units (\"RSUs\") awarded under the Issuer's 2023 Stock Option and Incentive Plan (the \"Plan\"), each representing the contingent right to receive one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), upon vesting and settlement. The RSUs vest as follows: (i) 50% of the RSUs will vest in eight equal quarterly installments, with the first such installment vesting on May 15, 2026, and (ii) thereafter the remaining 50% of the RSUs will vest in four equal quarterly installments, subject to the Reporting Person's continued service on each such vesting date."}],"balance_after":677576,"source":{"system":"sec-edgar","filing":"0001470831-26-000380","document":"wk-form4_1776471055.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1835830/000147083126000380/wk-form4_1776471055.xml","form_type":"4"}},{"id":807314,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":43558,"kind":"person","name":"Bialecki Andrew","position":1,"cik":"0001991099","reported_name":"Bialecki Andrew","relationship":{"director":true,"officer":true,"ten_percent_owner":true,"other":false,"officer_title":"Co-Chief Executive Officer"}}],"security":"Series B Common Stock","published_at":"2026-04-17T00:04:13.000Z","date":"2026-04-14","kind":"exercise","planned":true,"acquired":false,"shares":200000,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"derivative.exercise_price","element":"conversionOrExercisePrice","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 20, 2025."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"derivative.expiration_date","element":"expirationDate","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."}],"balance_after":67344118,"derivative":{"underlying":"Series A Common Stock","underlying_shares":200000},"source":{"system":"sec-edgar","filing":"0001470831-26-000375","document":"wk-form4_1776384250.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":4,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000375/wk-form4_1776384250.xml","form_type":"4"}},{"id":807313,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":43558,"kind":"person","name":"Bialecki Andrew","position":1,"cik":"0001991099","reported_name":"Bialecki Andrew","relationship":{"director":true,"officer":true,"ten_percent_owner":true,"other":false,"officer_title":"Co-Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2026-04-17T00:04:13.000Z","date":"2026-04-14","kind":"sale","planned":true,"acquired":false,"shares":90858,"price":16.94,"value":1539134.52,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 20, 2025."},{"field":"price","element":"transactionPricePerShare","label":"F4","text":"The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $16.85 to $17.03 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."}],"balance_after":0,"source":{"system":"sec-edgar","filing":"0001470831-26-000375","document":"wk-form4_1776384250.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":3,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000375/wk-form4_1776384250.xml","form_type":"4"}},{"id":807312,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":43558,"kind":"person","name":"Bialecki Andrew","position":1,"cik":"0001991099","reported_name":"Bialecki Andrew","relationship":{"director":true,"officer":true,"ten_percent_owner":true,"other":false,"officer_title":"Co-Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2026-04-17T00:04:13.000Z","date":"2026-04-14","kind":"sale","planned":true,"acquired":false,"shares":109142,"price":17.39,"value":1897979.38,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 20, 2025."},{"field":"price","element":"transactionPricePerShare","label":"F3","text":"The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $17.035 to $18.03 per share. 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The Series B Common Stock has no expiration date."},{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 20, 2025."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"derivative.expiration_date","element":"expirationDate","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. 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The shares were sold in multiple transactions at prices ranging from $18.31 to $18.94 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."}],"balance_after":0,"source":{"system":"sec-edgar","filing":"0001470831-26-000355","document":"wk-form4_1775779441.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000355/wk-form4_1775779441.xml","form_type":"4"}},{"id":811652,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":43558,"kind":"person","name":"Bialecki Andrew","position":1,"cik":"0001991099","reported_name":"Bialecki Andrew","relationship":{"director":true,"officer":true,"ten_percent_owner":true,"other":false,"officer_title":"Co-Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2026-04-10T00:04:04.000Z","date":"2026-04-07","kind":"exercise","planned":true,"acquired":true,"shares":200000,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 20, 2025."},{"field":"price","element":"transactionPricePerShare","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. 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The Series B Common Stock has no expiration date."},{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 20, 2025."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"derivative.expiration_date","element":"expirationDate","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. 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The shares were sold in multiple transactions at prices ranging from $18.85 to $19.75 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."}],"balance_after":0,"source":{"system":"sec-edgar","filing":"0001470831-26-000342","document":"wk-form4_1775174663.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000342/wk-form4_1775174663.xml","form_type":"4"}},{"id":820140,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":43558,"kind":"person","name":"Bialecki Andrew","position":1,"cik":"0001991099","reported_name":"Bialecki Andrew","relationship":{"director":true,"officer":true,"ten_percent_owner":true,"other":false,"officer_title":"Co-Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2026-04-03T00:04:26.000Z","date":"2026-03-31","kind":"exercise","planned":true,"acquired":true,"shares":200000,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 20, 2025."},{"field":"price","element":"transactionPricePerShare","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. 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The Series B Common Stock has no expiration date."},{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 20, 2025."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"derivative.expiration_date","element":"expirationDate","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. 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The shares were sold in multiple transactions at prices ranging from $17.77 to $18.65 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."}],"balance_after":0,"source":{"system":"sec-edgar","filing":"0001470831-26-000318","document":"wk-form4_1774569691.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000318/wk-form4_1774569691.xml","form_type":"4"}},{"id":827471,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":43558,"kind":"person","name":"Bialecki Andrew","position":1,"cik":"0001991099","reported_name":"Bialecki Andrew","relationship":{"director":true,"officer":true,"ten_percent_owner":true,"other":false,"officer_title":"Co-Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2026-03-27T00:01:33.000Z","date":"2026-03-24","kind":"exercise","planned":true,"acquired":true,"shares":200000,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 20, 2025."},{"field":"price","element":"transactionPricePerShare","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. 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The Series B Common Stock has no expiration date."},{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 20, 2025."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"derivative.expiration_date","element":"expirationDate","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. 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The shares were sold in multiple transactions at prices ranging from $19.10 to $19.32 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."}],"balance_after":0,"source":{"system":"sec-edgar","filing":"0001470831-26-000299","document":"wk-form4_1773964773.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":3,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000299/wk-form4_1773964773.xml","form_type":"4"}},{"id":833696,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":43558,"kind":"person","name":"Bialecki Andrew","position":1,"cik":"0001991099","reported_name":"Bialecki Andrew","relationship":{"director":true,"officer":true,"ten_percent_owner":true,"other":false,"officer_title":"Co-Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2026-03-19T23:59:36.000Z","date":"2026-03-17","kind":"sale","planned":true,"acquired":false,"shares":97379,"price":19.6,"value":1908628.4,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 20, 2025."},{"field":"price","element":"transactionPricePerShare","label":"F3","text":"The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $19.33 to $20.32 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."}],"balance_after":102621,"source":{"system":"sec-edgar","filing":"0001470831-26-000299","document":"wk-form4_1773964773.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000299/wk-form4_1773964773.xml","form_type":"4"}},{"id":833695,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":43558,"kind":"person","name":"Bialecki Andrew","position":1,"cik":"0001991099","reported_name":"Bialecki Andrew","relationship":{"director":true,"officer":true,"ten_percent_owner":true,"other":false,"officer_title":"Co-Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2026-03-19T23:59:36.000Z","date":"2026-03-17","kind":"exercise","planned":true,"acquired":true,"shares":200000,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 20, 2025."},{"field":"price","element":"transactionPricePerShare","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."}],"balance_after":200000,"source":{"system":"sec-edgar","filing":"0001470831-26-000299","document":"wk-form4_1773964773.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000299/wk-form4_1773964773.xml","form_type":"4"}},{"id":844161,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":18020,"kind":"person","name":"Edmond Landon","position":1,"cik":"0001991399","reported_name":"Edmond Landon","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Chief Legal Officer"}}],"security":"Series A Common Stock","published_at":"2026-03-13T23:58:56.000Z","date":"2026-03-12","kind":"sale","planned":true,"acquired":false,"shares":14366,"price":20.15,"value":289474.9,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on August 21, 2025."},{"field":"price","element":"transactionPricePerShare","label":"F2","text":"The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $20.00 to $20.45 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."},{"field":"balance_after","element":"sharesOwnedFollowingTransaction","label":"F3","text":"Consists of (i) 83,955 shares of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and (ii) 228,407 unvested restricted stock units awarded under the Issuer's 2023 Stock Option and Incentive Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement."}],"balance_after":312362,"source":{"system":"sec-edgar","filing":"0001470831-26-000272","document":"wk-form4_1773446333.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1991399/000147083126000272/wk-form4_1773446333.xml","form_type":"4"}},{"id":843401,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":21993,"kind":"person","name":"Whalen Amanda","position":1,"cik":"0001991131","reported_name":"Whalen Amanda","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Chief Financial Officer"}}],"security":"Series A Common Stock","published_at":"2026-03-13T23:57:52.000Z","date":"2026-03-12","kind":"sale","planned":true,"acquired":false,"shares":5077,"price":19.34,"value":98189.18,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on August 21, 2025."},{"field":"price","element":"transactionPricePerShare","label":"F3","text":"The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $19.27 to $19.38 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."},{"field":"balance_after","element":"sharesOwnedFollowingTransaction","label":"F4","text":"Consists of (i) 52,394 shares of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and (ii) 360,031 unvested restricted stock units awarded under the Issuer's 2023 Stock Option and Incentive Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement."}],"balance_after":412425,"source":{"system":"sec-edgar","filing":"0001470831-26-000270","document":"wk-form4_1773446269.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1835830/000147083126000270/wk-form4_1773446269.xml","form_type":"4"}},{"id":843400,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":21993,"kind":"person","name":"Whalen Amanda","position":1,"cik":"0001991131","reported_name":"Whalen Amanda","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Chief Financial Officer"}}],"security":"Series A Common Stock","published_at":"2026-03-13T23:57:52.000Z","date":"2026-03-12","kind":"sale","planned":true,"acquired":false,"shares":8923,"price":19.72,"value":175961.56,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on August 21, 2025."},{"field":"price","element":"transactionPricePerShare","label":"F2","text":"The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $19.385 to $20.38 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."}],"balance_after":417502,"source":{"system":"sec-edgar","filing":"0001470831-26-000270","document":"wk-form4_1773446269.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1835830/000147083126000270/wk-form4_1773446269.xml","form_type":"4"}},{"id":846508,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":43558,"kind":"person","name":"Bialecki Andrew","position":1,"cik":"0001991099","reported_name":"Bialecki Andrew","relationship":{"director":true,"officer":true,"ten_percent_owner":true,"other":false,"officer_title":"Co-Chief Executive Officer"}}],"security":"Series B Common Stock","published_at":"2026-03-13T01:47:25.000Z","date":"2026-03-10","kind":"exercise","planned":true,"acquired":false,"shares":206827,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"derivative.exercise_price","element":"conversionOrExercisePrice","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 20, 2025."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"derivative.expiration_date","element":"expirationDate","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."}],"balance_after":68344118,"derivative":{"underlying":"Series A Common Stock","underlying_shares":206827},"source":{"system":"sec-edgar","filing":"0001470831-26-000262","document":"wk-form4_1773366442.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":4,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000262/wk-form4_1773366442.xml","form_type":"4"}},{"id":846507,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":43558,"kind":"person","name":"Bialecki Andrew","position":1,"cik":"0001991099","reported_name":"Bialecki Andrew","relationship":{"director":true,"officer":true,"ten_percent_owner":true,"other":false,"officer_title":"Co-Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2026-03-13T01:47:25.000Z","date":"2026-03-10","kind":"sale","planned":true,"acquired":false,"shares":700,"price":19.34,"value":13538.0,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 20, 2025."},{"field":"price","element":"transactionPricePerShare","label":"F4","text":"The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $19.28 to $19.37 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."}],"balance_after":0,"source":{"system":"sec-edgar","filing":"0001470831-26-000262","document":"wk-form4_1773366442.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":3,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000262/wk-form4_1773366442.xml","form_type":"4"}},{"id":846506,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":43558,"kind":"person","name":"Bialecki Andrew","position":1,"cik":"0001991099","reported_name":"Bialecki Andrew","relationship":{"director":true,"officer":true,"ten_percent_owner":true,"other":false,"officer_title":"Co-Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2026-03-13T01:47:25.000Z","date":"2026-03-10","kind":"sale","planned":true,"acquired":false,"shares":206127,"price":19.96,"value":4114294.92,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 20, 2025."},{"field":"price","element":"transactionPricePerShare","label":"F3","text":"The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $19.375 to $20.37 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."}],"balance_after":700,"source":{"system":"sec-edgar","filing":"0001470831-26-000262","document":"wk-form4_1773366442.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000262/wk-form4_1773366442.xml","form_type":"4"}},{"id":846505,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":43558,"kind":"person","name":"Bialecki Andrew","position":1,"cik":"0001991099","reported_name":"Bialecki Andrew","relationship":{"director":true,"officer":true,"ten_percent_owner":true,"other":false,"officer_title":"Co-Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2026-03-13T01:47:25.000Z","date":"2026-03-10","kind":"exercise","planned":true,"acquired":true,"shares":206827,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 20, 2025."},{"field":"price","element":"transactionPricePerShare","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."}],"balance_after":206827,"source":{"system":"sec-edgar","filing":"0001470831-26-000262","document":"wk-form4_1773366442.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000262/wk-form4_1773366442.xml","form_type":"4"}},{"id":858899,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":18020,"kind":"person","name":"Edmond Landon","position":1,"cik":"0001991399","reported_name":"Edmond Landon","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Chief Legal Officer"}}],"security":"Series A Common Stock","published_at":"2026-03-06T02:34:32.000Z","date":"2026-03-05","kind":"sale","planned":true,"acquired":false,"shares":15093,"price":20.16,"value":304274.88,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on August 21, 2025."},{"field":"price","element":"transactionPricePerShare","label":"F2","text":"The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $20.00 to $20.63 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."},{"field":"balance_after","element":"sharesOwnedFollowingTransaction","label":"F3","text":"Consists of (i) 98,321 shares of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and (ii) 228,407 unvested restricted stock units awarded under the Issuer's 2023 Stock Option and Incentive Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement."}],"balance_after":326728,"source":{"system":"sec-edgar","filing":"0001470831-26-000249","document":"wk-form4_1772764470.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1991399/000147083126000249/wk-form4_1772764470.xml","form_type":"4"}},{"id":858903,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":43558,"kind":"person","name":"Bialecki Andrew","position":1,"cik":"0001991099","reported_name":"Bialecki Andrew","relationship":{"director":true,"officer":true,"ten_percent_owner":true,"other":false,"officer_title":"Co-Chief Executive Officer"}}],"security":"Series B Common Stock","published_at":"2026-03-06T02:32:29.000Z","date":"2026-03-03","kind":"exercise","planned":true,"acquired":false,"shares":200000,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"derivative.exercise_price","element":"conversionOrExercisePrice","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 20, 2025."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"derivative.expiration_date","element":"expirationDate","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. 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The shares were sold in multiple transactions at prices ranging from $17.52 to $18.21 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."}],"balance_after":0,"source":{"system":"sec-edgar","filing":"0001470831-26-000247","document":"wk-form4_1772764346.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":3,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000247/wk-form4_1772764346.xml","form_type":"4"}},{"id":858901,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":43558,"kind":"person","name":"Bialecki Andrew","position":1,"cik":"0001991099","reported_name":"Bialecki Andrew","relationship":{"director":true,"officer":true,"ten_percent_owner":true,"other":false,"officer_title":"Co-Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2026-03-06T02:32:29.000Z","date":"2026-03-03","kind":"sale","planned":true,"acquired":false,"shares":154022,"price":18.86,"value":2904854.92,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 20, 2025."},{"field":"price","element":"transactionPricePerShare","label":"F3","text":"The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $18.22 to $19.21 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."}],"balance_after":45978,"source":{"system":"sec-edgar","filing":"0001470831-26-000247","document":"wk-form4_1772764346.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000247/wk-form4_1772764346.xml","form_type":"4"}},{"id":858900,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":43558,"kind":"person","name":"Bialecki Andrew","position":1,"cik":"0001991099","reported_name":"Bialecki Andrew","relationship":{"director":true,"officer":true,"ten_percent_owner":true,"other":false,"officer_title":"Co-Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2026-03-06T02:32:29.000Z","date":"2026-03-03","kind":"exercise","planned":true,"acquired":true,"shares":200000,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 20, 2025."},{"field":"price","element":"transactionPricePerShare","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."}],"balance_after":200000,"source":{"system":"sec-edgar","filing":"0001470831-26-000247","document":"wk-form4_1772764346.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000247/wk-form4_1772764346.xml","form_type":"4"}},{"id":879950,"issuer":{"id":3775,"kind":"organization","name":"Klaviyo, Inc.","symbol":"KVYO"},"owners":[{"id":43558,"kind":"person","name":"Bialecki Andrew","position":1,"cik":"0001991099","reported_name":"Bialecki Andrew","relationship":{"director":true,"officer":true,"ten_percent_owner":true,"other":false,"officer_title":"Co-Chief Executive Officer"}}],"security":"Series B Common Stock","published_at":"2026-02-27T02:30:10.000Z","date":"2026-02-24","kind":"exercise","planned":true,"acquired":false,"shares":200000,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"derivative.exercise_price","element":"conversionOrExercisePrice","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"kind","element":"transactionCoding","label":"F1","text":"These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 20, 2025."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."},{"field":"derivative.expiration_date","element":"expirationDate","label":"F2","text":"Each share of the Issuer's Series B Common Stock, par value $0.001 per share (\"Series B Common Stock\"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share (\"Series A Common Stock\"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date."}],"balance_after":68750945,"derivative":{"underlying":"Series A Common Stock","underlying_shares":200000},"source":{"system":"sec-edgar","filing":"0001470831-26-000222","document":"wk-form4_1772159407.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":4,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000222/wk-form4_1772159407.xml","form_type":"4"}}],"next_cursor":"2026-02-27T02:30:10.000000Z,879950"}