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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 $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. 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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 $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. 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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 $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. 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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 $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. 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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. 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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. 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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. 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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 $19.28 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. 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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 $17.52 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. 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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 $15.83 to $16.53 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":"0001470831-26-000222","document":"wk-form4_1772159407.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":3,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000222/wk-form4_1772159407.xml","form_type":"4"}},{"id":879948,"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":"2026-02-27T02:30:10.000Z","date":"2026-02-24","kind":"sale","planned":true,"acquired":false,"shares":160356,"price":16.86,"value":2703602.16,"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 $16.535 to $17.53 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":39644,"source":{"system":"sec-edgar","filing":"0001470831-26-000222","document":"wk-form4_1772159407.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000222/wk-form4_1772159407.xml","form_type":"4"}},{"id":879947,"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":"2026-02-27T02:30:10.000Z","date":"2026-02-24","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. The Series B Common Stock has no expiration date."}],"balance_after":200000,"source":{"system":"sec-edgar","filing":"0001470831-26-000222","document":"wk-form4_1772159407.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000222/wk-form4_1772159407.xml","form_type":"4"}},{"id":927985,"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":"2026-01-29T21:29:45.000Z","date":"2026-01-27","kind":"exercise","planned":true,"acquired":false,"shares":155219,"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 $24.82 to $25.00 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":"0001470831-26-000061","document":"wk-form4_1769722181.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":3,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000061/wk-form4_1769722181.xml","form_type":"4"}},{"id":927983,"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":"2026-01-29T21:29:45.000Z","date":"2026-01-27","kind":"sale","planned":true,"acquired":false,"shares":150689,"price":25.34,"value":3818459.26,"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 $25.01 to $26.00 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":4530,"source":{"system":"sec-edgar","filing":"0001470831-26-000061","document":"wk-form4_1769722181.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000061/wk-form4_1769722181.xml","form_type":"4"}},{"id":927982,"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":"2026-01-29T21:29:45.000Z","date":"2026-01-27","kind":"exercise","planned":true,"acquired":true,"shares":155219,"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 $23.15 to $23.46 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":"0001470831-26-000051","document":"wk-form4_1769117357.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":3,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000051/wk-form4_1769117357.xml","form_type":"4"}},{"id":933522,"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":"2026-01-22T21:29:20.000Z","date":"2026-01-20","kind":"sale","planned":true,"acquired":false,"shares":167130,"price":24.16,"value":4037860.8,"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 $23.48 to $24.46 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":796,"source":{"system":"sec-edgar","filing":"0001470831-26-000051","document":"wk-form4_1769117357.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000051/wk-form4_1769117357.xml","form_type":"4"}},{"id":933521,"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":"2026-01-22T21:29:20.000Z","date":"2026-01-20","kind":"exercise","planned":true,"acquired":true,"shares":167926,"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 $27.10 to $27.42 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":"0001470831-26-000037","document":"wk-form4_1768518127.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":3,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000037/wk-form4_1768518127.xml","form_type":"4"}},{"id":938586,"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":"2026-01-15T23:02:10.000Z","date":"2026-01-13","kind":"sale","planned":true,"acquired":false,"shares":50319,"price":27.62,"value":1389810.78,"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 $27.425 to $28.42 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":90327,"source":{"system":"sec-edgar","filing":"0001470831-26-000037","document":"wk-form4_1768518127.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000037/wk-form4_1768518127.xml","form_type":"4"}},{"id":938585,"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":"2026-01-15T23:02:10.000Z","date":"2026-01-13","kind":"exercise","planned":true,"acquired":true,"shares":140646,"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":140646,"source":{"system":"sec-edgar","filing":"0001470831-26-000037","document":"wk-form4_1768518127.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000037/wk-form4_1768518127.xml","form_type":"4"}},{"id":943377,"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":"2026-01-08T21:31:28.000Z","date":"2026-01-07","kind":"exercise","planned":true,"acquired":false,"shares":16649,"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 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 $30.00  to $30.06  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":"0001470831-26-000022","document":"wk-form4_1767907885.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":5,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000022/wk-form4_1767907885.xml","form_type":"4"}},{"id":943374,"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":"2026-01-08T21:31:28.000Z","date":"2026-01-07","kind":"exercise","planned":true,"acquired":true,"shares":16649,"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 shares were sold in multiple transactions at prices ranging from $28.42 to $28.54 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":"0001470831-26-000022","document":"wk-form4_1767907885.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":3,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000022/wk-form4_1767907885.xml","form_type":"4"}},{"id":943372,"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":"2026-01-08T21:31:28.000Z","date":"2026-01-06","kind":"sale","planned":true,"acquired":false,"shares":135122,"price":28.92,"value":3907728.24,"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 $28.545 to $29.54 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":2382,"source":{"system":"sec-edgar","filing":"0001470831-26-000022","document":"wk-form4_1767907885.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083126000022/wk-form4_1767907885.xml","form_type":"4"}},{"id":943371,"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":"2026-01-08T21:31:28.000Z","date":"2026-01-06","kind":"exercise","planned":true,"acquired":true,"shares":137504,"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 shares were sold in multiple transactions at prices ranging from $31.57 to $32.30 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":"0001470831-25-000452","document":"wk-form4_1766523997.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":3,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083125000452/wk-form4_1766523997.xml","form_type":"4"}},{"id":959831,"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":"Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2025-12-23T21:06:42.000Z","date":"2025-12-22","kind":"sale","planned":true,"acquired":false,"shares":93066,"price":33.05,"value":3075831.3,"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 $32.38 to $33.35 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":6934,"source":{"system":"sec-edgar","filing":"0001470831-25-000452","document":"wk-form4_1766523997.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083125000452/wk-form4_1766523997.xml","form_type":"4"}},{"id":959830,"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":"Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2025-12-23T21:06:42.000Z","date":"2025-12-22","kind":"exercise","planned":true,"acquired":true,"shares":100000,"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":"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 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 $30.00 to $30.71 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":"0001470831-25-000431","document":"wk-form4_1766010254.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":4,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083125000431/wk-form4_1766010254.xml","form_type":"4"}},{"id":965410,"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":"Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2025-12-17T22:24:19.000Z","date":"2025-12-17","kind":"exercise","planned":true,"acquired":true,"shares":100000,"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 shares were sold in multiple transactions at prices ranging from $28.58 to $29.42 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":"0001470831-25-000431","document":"wk-form4_1766010254.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083125000431/wk-form4_1766010254.xml","form_type":"4"}},{"id":965408,"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":"Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2025-12-17T22:24:19.000Z","date":"2025-12-16","kind":"exercise","planned":true,"acquired":true,"shares":138648,"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":"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":69907537,"derivative":{"underlying":"Series A Common Stock","underlying_shares":3419000},"source":{"system":"sec-edgar","filing":"0001470831-25-000395","document":"wk-form4_1765488141.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":13,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083125000395/wk-form4_1765488141.xml","form_type":"4"}},{"id":972829,"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":"Chief Executive Officer"}}],"security":"Series B Common Stock","published_at":"2025-12-11T21:22:24.000Z","date":"2025-12-11","kind":"exercise","planned":true,"acquired":false,"shares":17777,"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":73326537,"derivative":{"underlying":"Series A Common Stock","underlying_shares":17777},"source":{"system":"sec-edgar","filing":"0001470831-25-000395","document":"wk-form4_1765488141.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":12,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083125000395/wk-form4_1765488141.xml","form_type":"4"}},{"id":972828,"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":"Chief Executive Officer"}}],"security":"Series B Common Stock","published_at":"2025-12-11T21:22:24.000Z","date":"2025-12-10","kind":"exercise","planned":true,"acquired":false,"shares":82223,"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":73344314,"derivative":{"underlying":"Series A Common Stock","underlying_shares":82223},"source":{"system":"sec-edgar","filing":"0001470831-25-000395","document":"wk-form4_1765488141.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":11,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083125000395/wk-form4_1765488141.xml","form_type":"4"}},{"id":972827,"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":"Chief Executive Officer"}}],"security":"Series B Common Stock","published_at":"2025-12-11T21:22:24.000Z","date":"2025-12-09","kind":"exercise","planned":true,"acquired":false,"shares":131362,"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":73426537,"derivative":{"underlying":"Series A Common Stock","underlying_shares":131362},"source":{"system":"sec-edgar","filing":"0001470831-25-000395","document":"wk-form4_1765488141.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":10,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083125000395/wk-form4_1765488141.xml","form_type":"4"}},{"id":972826,"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":"Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2025-12-11T21:22:24.000Z","date":"2025-12-11","kind":"gift","planned":true,"acquired":false,"shares":3419000,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F7","text":"Represents a bona fide gift of 3,419,000 shares of stock from the Reporting Person to a donor-advised fund. The Reporting Person directed the transfer of 3,419,000 shares of their Series B Common Stock, resulting in the automatic conversion of the shares into Series A Common Stock upon execution of the transfer pursuant to the Issuer's certificate of incorporation."}],"balance_after":0,"source":{"system":"sec-edgar","filing":"0001470831-25-000395","document":"wk-form4_1765488141.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":9,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083125000395/wk-form4_1765488141.xml","form_type":"4"}},{"id":972825,"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":"Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2025-12-11T21:22:24.000Z","date":"2025-12-11","kind":"exercise","planned":true,"acquired":true,"shares":3419000,"ownership":{"direct":true},"footnotes":[{"field":"price","element":"transactionPricePerShare","label":"F6","text":"The Reporting Person directed the transfer of 3,419,000 shares of their Series B Common Stock in connection with a bona fide gift to a donor-advised fund, resulting in the automatic conversion of\nthe shares into Series A Common Stock upon execution of the transfer pursuant to the Issuer's certificate of incorporation."}],"balance_after":3419000,"source":{"system":"sec-edgar","filing":"0001470831-25-000395","document":"wk-form4_1765488141.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":8,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083125000395/wk-form4_1765488141.xml","form_type":"4"}},{"id":972824,"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":"Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2025-12-11T21:22:24.000Z","date":"2025-12-11","kind":"sale","planned":true,"acquired":false,"shares":17777,"price":30,"value":533310.0,"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."}],"balance_after":0,"source":{"system":"sec-edgar","filing":"0001470831-25-000395","document":"wk-form4_1765488141.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":7,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083125000395/wk-form4_1765488141.xml","form_type":"4"}},{"id":972823,"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":"Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2025-12-11T21:22:24.000Z","date":"2025-12-11","kind":"exercise","planned":true,"acquired":true,"shares":17777,"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":17777,"source":{"system":"sec-edgar","filing":"0001470831-25-000395","document":"wk-form4_1765488141.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":6,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083125000395/wk-form4_1765488141.xml","form_type":"4"}},{"id":972822,"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":"Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2025-12-11T21:22:24.000Z","date":"2025-12-10","kind":"sale","planned":true,"acquired":false,"shares":82223,"price":30.12,"value":2476556.76,"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":"F5","text":"The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $30.00 to $30.45 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":0,"source":{"system":"sec-edgar","filing":"0001470831-25-000395","document":"wk-form4_1765488141.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":5,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083125000395/wk-form4_1765488141.xml","form_type":"4"}},{"id":972821,"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":"Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2025-12-11T21:22:24.000Z","date":"2025-12-10","kind":"exercise","planned":true,"acquired":true,"shares":82223,"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":82223,"source":{"system":"sec-edgar","filing":"0001470831-25-000395","document":"wk-form4_1765488141.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":4,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083125000395/wk-form4_1765488141.xml","form_type":"4"}},{"id":972820,"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":"Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2025-12-11T21:22:24.000Z","date":"2025-12-09","kind":"sale","planned":true,"acquired":false,"shares":800,"price":28.84,"value":23072.0,"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 $28.81 to $28.89 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":"0001470831-25-000395","document":"wk-form4_1765488141.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":3,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083125000395/wk-form4_1765488141.xml","form_type":"4"}},{"id":972819,"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":"Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2025-12-11T21:22:24.000Z","date":"2025-12-09","kind":"sale","planned":true,"acquired":false,"shares":130562,"price":29.42,"value":3841134.04,"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 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 $28.92 to $29.89 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":800,"source":{"system":"sec-edgar","filing":"0001470831-25-000395","document":"wk-form4_1765488141.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083125000395/wk-form4_1765488141.xml","form_type":"4"}},{"id":972818,"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":"Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2025-12-11T21:22:24.000Z","date":"2025-12-09","kind":"exercise","planned":true,"acquired":true,"shares":131362,"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":131362,"source":{"system":"sec-edgar","filing":"0001470831-25-000395","document":"wk-form4_1765488141.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083125000395/wk-form4_1765488141.xml","form_type":"4"}},{"id":980479,"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":"Chief Executive Officer"}}],"security":"Series B Common Stock","published_at":"2025-12-04T23:50:43.000Z","date":"2025-12-04","kind":"exercise","planned":true,"acquired":false,"shares":952,"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. 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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 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 $28.20 to $28.87 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":"0001470831-25-000382","document":"wk-form4_1764892241.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083125000382/wk-form4_1764892241.xml","form_type":"4"}},{"id":980474,"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":"Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2025-12-04T23:50:43.000Z","date":"2025-12-02","kind":"exercise","planned":true,"acquired":true,"shares":142045,"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 $27.39 to $28.20 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":"0001470831-25-000372","document":"wk-form4_1764191533.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083125000372/wk-form4_1764191533.xml","form_type":"4"}},{"id":987339,"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":"Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2025-11-26T21:12:19.000Z","date":"2025-11-24","kind":"exercise","planned":true,"acquired":true,"shares":144717,"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":"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 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":73992942,"derivative":{"underlying":"Series A Common Stock","underlying_shares":140464},"source":{"system":"sec-edgar","filing":"0001470831-25-000313","document":"wk-form4_1763069095.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":3,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083125000313/wk-form4_1763069095.xml","form_type":"4"}},{"id":1000457,"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":"Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2025-11-13T21:24:59.000Z","date":"2025-11-11","kind":"sale","planned":true,"acquired":false,"shares":140464,"price":29.74,"value":4177399.36,"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":"F3","text":"The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $29.21 to $30.01 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":"0001470831-25-000313","document":"wk-form4_1763069095.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083125000313/wk-form4_1763069095.xml","form_type":"4"}},{"id":1000456,"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":"Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2025-11-13T21:24:59.000Z","date":"2025-11-11","kind":"exercise","planned":true,"acquired":true,"shares":140464,"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":140464,"source":{"system":"sec-edgar","filing":"0001470831-25-000313","document":"wk-form4_1763069095.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083125000313/wk-form4_1763069095.xml","form_type":"4"}},{"id":1017699,"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":"Chief Executive Officer"}}],"security":"Series B Common Stock","published_at":"2025-10-16T20:09:47.000Z","date":"2025-10-14","kind":"exercise","planned":true,"acquired":false,"shares":163331,"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":74133406,"derivative":{"underlying":"Series A Common Stock","underlying_shares":163331},"source":{"system":"sec-edgar","filing":"0001470831-25-000260","document":"wk-form4_1760645384.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":3,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083125000260/wk-form4_1760645384.xml","form_type":"4"}},{"id":1017698,"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":"Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2025-10-16T20:09:47.000Z","date":"2025-10-14","kind":"sale","planned":true,"acquired":false,"shares":163331,"price":24.37,"value":3980376.47,"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 $23.67 to $24.655 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":"0001470831-25-000260","document":"wk-form4_1760645384.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083125000260/wk-form4_1760645384.xml","form_type":"4"}},{"id":1017697,"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":"Chief Executive Officer"}}],"security":"Series A Common Stock","published_at":"2025-10-16T20:09:47.000Z","date":"2025-10-14","kind":"exercise","planned":true,"acquired":true,"shares":163331,"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":163331,"source":{"system":"sec-edgar","filing":"0001470831-25-000260","document":"wk-form4_1760645384.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000147083125000260/wk-form4_1760645384.xml","form_type":"4"}},{"id":1020919,"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":"Chief Executive Officer"}}],"security":"Series B Common Stock","published_at":"2025-10-09T20:01:41.000Z","date":"2025-10-07","kind":"exercise","planned":true,"acquired":false,"shares":159508,"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":74296737,"derivative":{"underlying":"Series A Common Stock","underlying_shares":159508},"source":{"system":"sec-edgar","filing":"0001991099-25-000003","document":"wk-form4_1760040098.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":4,"url":"https://www.sec.gov/Archives/edgar/data/1991099/000199109925000003/wk-form4_1760040098.xml","form_type":"4"}}],"next_cursor":"2025-10-09T20:01:41.000000Z,1020919"}