KVYO

SEC source: 0001835830-24-000112 · wk-form4_1732057767.xml · nonDerivative · entry 3

Whalen Amanda · CIK 0001991131 · Chief Financial Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 395,616

F4 · kind: These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on August 16, 2024.

F5 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $34.16 to $35.00 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.

F6 · balance_after: Consists of (i) 45,707 shares of Series A Common Stock and (ii) 349,909 unvested RSUs awarded under the Issuer's 2023 Stock Option and Incentive Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement.

SEC source: 0001835830-24-000113 · wk-form4_1732057869.xml · derivative · entry 5

Edmond Landon · CIK 0001991399 · Chief Legal Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 239,486

Underlying: Series A Common Stock · 16,666 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F2 · derivative.exercise_price: Each share of Series B Common Stock is convertible at any time at the option of the holder into one share of Series A Common Stock, and will automatically convert into Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

F1 · kind: Represents 16,666 shares of the Issuer's Series B Common Stock, par value $0.001 per share ("Series B Common Stock"), automatically converted into shares of the Issuer's Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), in connection with tax withholding obligations related to the vesting and settlement of restricted stock units ("RSUs").

F2 · derivative.exercise_date: Each share of Series B Common Stock is convertible at any time at the option of the holder into one share of Series A Common Stock, and will automatically convert into Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

F2 · derivative.expiration_date: Each share of Series B Common Stock is convertible at any time at the option of the holder into one share of Series A Common Stock, and will automatically convert into Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

SEC source: 0001835830-24-000113 · wk-form4_1732057869.xml · nonDerivative · entry 2

Edmond Landon · CIK 0001991399 · Chief Legal Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 236,621

F3 · kind: Represents shares of Series A Common Stock withheld by the Issuer to satisfy tax withholding obligations in connection with the vesting and settlement of RSUs.

SEC source: 0001835830-24-000113 · wk-form4_1732057869.xml · nonDerivative · entry 1

Edmond Landon · CIK 0001991399 · Chief Legal Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 262,409

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · kind: Represents 16,666 shares of the Issuer's Series B Common Stock, par value $0.001 per share ("Series B Common Stock"), automatically converted into shares of the Issuer's Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), in connection with tax withholding obligations related to the vesting and settlement of restricted stock units ("RSUs").

F2 · price: Each share of Series B Common Stock is convertible at any time at the option of the holder into one share of Series A Common Stock, and will automatically convert into Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

SEC source: 0001835830-24-000111 · wk-form4_1732057629.xml · nonDerivative · entry 1

Galvin Carmel · CIK 0001733091 · Chief People Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 649,372

F1 · kind: Represents shares of the Issuer's Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), withheld by the Issuer to satisfy tax withholding obligations in connection with the vesting and settlement of restricted stock units ("RSUs").

F2 · balance_after: Consists of (i) 44,621 shares of Series A Common Stock and (ii) 604,751 unvested RSUs awarded under the Issuer's 2023 Stock Option and Incentive Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement.

SEC source: 0001835830-24-000114 · wk-form4_1732057965.xml · derivative · entry 5

Rowland Stephen Eric · CIK 0001639368 · President

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 651,658

Underlying: Series A Common Stock · 22,957 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F2 · derivative.exercise_price: Each share of Series B Common Stock is convertible at any time at the option of the holder into one share of Series A Common Stock, and will automatically convert into Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

F1 · kind: Represents 22,957 shares of the Issuer's Series B Common Stock, par value $0.001 per share ("Series B Common Stock"), automatically converted into shares of the Issuer's Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), in connection with tax withholding obligations related to the vesting and settlement of restricted stock units ("RSUs").

F2 · derivative.exercise_date: Each share of Series B Common Stock is convertible at any time at the option of the holder into one share of Series A Common Stock, and will automatically convert into Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

F2 · derivative.expiration_date: Each share of Series B Common Stock is convertible at any time at the option of the holder into one share of Series A Common Stock, and will automatically convert into Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

SEC source: 0001835830-24-000114 · wk-form4_1732057965.xml · nonDerivative · entry 2

Rowland Stephen Eric · CIK 0001639368 · President

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 186,785

F3 · kind: Represents shares of Series A Common Stock withheld by the Issuer to satisfy tax withholding obligations in connection with the vesting and settlement of RSUs.

SEC source: 0001835830-24-000114 · wk-form4_1732057965.xml · nonDerivative · entry 1

Rowland Stephen Eric · CIK 0001639368 · President

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 215,445

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · kind: Represents 22,957 shares of the Issuer's Series B Common Stock, par value $0.001 per share ("Series B Common Stock"), automatically converted into shares of the Issuer's Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), in connection with tax withholding obligations related to the vesting and settlement of restricted stock units ("RSUs").

F2 · price: Each share of Series B Common Stock is convertible at any time at the option of the holder into one share of Series A Common Stock, and will automatically convert into Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

SEC source: 0001835830-24-000112 · wk-form4_1732057767.xml · derivative · entry 4

Whalen Amanda · CIK 0001991131 · Chief Financial Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 586,262

Underlying: Series A Common Stock · 18,856 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F2 · derivative.exercise_price: Each share of Series B Common Stock is convertible at any time at the option of the holder into one share of Series A Common Stock, and will automatically convert into Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

F1 · kind: Represents 18,856 shares of the Issuer's Series B Common Stock, par value $0.001 per share ("Series B Common Stock"), automatically converted into shares of the Issuer's Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), in connection with tax withholding obligations relating to the vesting and settlement of restricted stock units ("RSUs").

F2 · derivative.exercise_date: Each share of Series B Common Stock is convertible at any time at the option of the holder into one share of Series A Common Stock, and will automatically convert into Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

F2 · derivative.expiration_date: Each share of Series B Common Stock is convertible at any time at the option of the holder into one share of Series A Common Stock, and will automatically convert into Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

F7 · balance_after: Consists of (i) 203,970 shares of Series B Common Stock and (ii) 382,292 unvested RSUs awarded under the Issuer's 2015 Stock Incentive Plan, each representing the contingent right to receive one share of Series B Common Stock upon vesting and settlement.

SEC source: 0001835830-24-000112 · wk-form4_1732057767.xml · nonDerivative · entry 2

Whalen Amanda · CIK 0001991131 · Chief Financial Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 410,616

F3 · kind: Represents shares of Series A Common Stock withheld by the Issuer to satisfy tax withholding obligations in connection with the vesting and settlement of RSUs.

SEC source: 0001835830-24-000112 · wk-form4_1732057767.xml · nonDerivative · entry 1

Whalen Amanda · CIK 0001991131 · Chief Financial Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 441,669

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · kind: Represents 18,856 shares of the Issuer's Series B Common Stock, par value $0.001 per share ("Series B Common Stock"), automatically converted into shares of the Issuer's Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), in connection with tax withholding obligations relating to the vesting and settlement of restricted stock units ("RSUs").

F2 · price: Each share of Series B Common Stock is convertible at any time at the option of the holder into one share of Series A Common Stock, and will automatically convert into Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

SEC source: 0000950170-24-127985 · ownership.xml · derivative · entry 3

SUMMIT PARTNERS L P · CIK 0000830588 · 10% owner

Summit Partners Growth Equity Fund IX-A, L.P. · CIK 0001634415 · 10% owner

Summit Partners Growth Equity Fund IX-B, L.P. · CIK 0001634426 · 10% owner

Summit Partners Co-Invest (Kiwi), LP · CIK 0001830877 · 10% owner

SUMMIT INVESTORS GE IX/VC IV, LLC · CIK 0001654074 · 10% owner

SUMMIT INVESTORS GE IX/VC IV (UK), L.P. · CIK 0001846709 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 42,927,778

Underlying: Series A Common Stock, par value $0.001 per share · 3,500,000 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: The Series B common stock, par value $0.001 per share ("Series B Common Stock"), is convertible into an equal number of shares of Series A common stock, par value $0.001 per share ("Series A Common Stock"), at any time, at the holder's election, and has no expiration date. Each share of Series B Common Stock will automatically convert into Series A Common Stock upon the earlier of (i) the date specified by 66-2/3% of the outstanding shares of Series B Common Stock, voting as a single series; (ii) following the seventh anniversary of the closing of Klaviyo, Inc.'s (the "Company") initial public offering; or (iii) any transfer, whether or not for value, except for certain permitted transfers described in the Company's certificate of incorporation.

F1 · derivative.exercise_date: The Series B common stock, par value $0.001 per share ("Series B Common Stock"), is convertible into an equal number of shares of Series A common stock, par value $0.001 per share ("Series A Common Stock"), at any time, at the holder's election, and has no expiration date. Each share of Series B Common Stock will automatically convert into Series A Common Stock upon the earlier of (i) the date specified by 66-2/3% of the outstanding shares of Series B Common Stock, voting as a single series; (ii) following the seventh anniversary of the closing of Klaviyo, Inc.'s (the "Company") initial public offering; or (iii) any transfer, whether or not for value, except for certain permitted transfers described in the Company's certificate of incorporation.

F1 · derivative.expiration_date: The Series B common stock, par value $0.001 per share ("Series B Common Stock"), is convertible into an equal number of shares of Series A common stock, par value $0.001 per share ("Series A Common Stock"), at any time, at the holder's election, and has no expiration date. Each share of Series B Common Stock will automatically convert into Series A Common Stock upon the earlier of (i) the date specified by 66-2/3% of the outstanding shares of Series B Common Stock, voting as a single series; (ii) following the seventh anniversary of the closing of Klaviyo, Inc.'s (the "Company") initial public offering; or (iii) any transfer, whether or not for value, except for certain permitted transfers described in the Company's certificate of incorporation.

F6 · balance_after: Consists of (i) 25,371,277 shares of Series B Common Stock held by Fund IX-A, (ii) 15,841,470 shares of Series B Common Stock held by Fund IX-B, (iii) 1,564,379 shares of Series B Common Stock held by Kiwi Co-Invest Fund, (iv) 133,345 shares of Series B Common Stock held by Fund IX/VC IV, and (v) 17,307 shares of Series B Common Stock held by Fund IX/VC IV (UK).

F2 · ownership.nature: Summit Partners, L.P. is the manager of Summit Partners GE IX, LLC, which is the general partner of Summit Partners GE IX, LP, which is the general partner of Summit Partners Growth Equity Fund IX-A, L.P. ("Fund IX-A") and Summit Partners Growth Equity Fund IX-B, L.P. ("Fund IX-B"). Summit Partners, L.P. is the managing member of Summit Partners Co-Invest Kiwi GP, LLC, which is the general partner of Summit Partners Co-Invest (Kiwi), L.P. ("Kiwi Co-Invest Fund"). Summit Master Company, LLC is the general partner of Summit Partners, L.P., which is the manager of Summit Investors Management, LLC, which is the manager of Summit Investors GE IX/VC IV, LLC ("Fund IX/VC IV") and the general partner of Summit Investors GE IX/VC IV (UK), L.P. ("Fund IX/VC IV (UK)").

F3 · ownership.nature: (continued from footnote 3) Summit Master Company, LLC, as the managing member of Summit Investors Management, LLC, has delegated voting and investment decisions with respect to the securities held by Fund IX/VC IV and Fund IX/VC IV (UK) to Summit Partners, L.P.

F4 · ownership.nature: The investment committee of Summit Partners, L.P., is currently composed of Peter Y. Chung, Scott C. Collins, and Peter L. Rottier, who may be deemed to have voting and dispositive authority over, and therefore beneficial ownership of, the reported securities. Each of the foregoing entities, Mr. Chung, Mr. Collins, and Mr. Rottier disclaims beneficial ownership of the shares, except to the extent of such person's or entity's pecuniary interest therein and the filing of this statement shall not be deemed an admission that any of the foregoing entities or persons are, for purposes of Section 16 of the Act or otherwise, the beneficial owner of any equity securities covered by this statement.

SEC source: 0000950170-24-127985 · ownership.xml · nonDerivative · entry 2

SUMMIT PARTNERS L P · CIK 0000830588 · 10% owner

Summit Partners Growth Equity Fund IX-A, L.P. · CIK 0001634415 · 10% owner

Summit Partners Growth Equity Fund IX-B, L.P. · CIK 0001634426 · 10% owner

Summit Partners Co-Invest (Kiwi), LP · CIK 0001830877 · 10% owner

SUMMIT INVESTORS GE IX/VC IV, LLC · CIK 0001654074 · 10% owner

SUMMIT INVESTORS GE IX/VC IV (UK), L.P. · CIK 0001846709 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnotes

Disclosed balance after: 346,707

F5 · balance_after: Consists of (i) 213,439 shares of Series A Common Stock held by Fund IX-A and (ii) 133,268 shares of Series A Common Stock held by Fund IX-B.

F2 · ownership.nature: Summit Partners, L.P. is the manager of Summit Partners GE IX, LLC, which is the general partner of Summit Partners GE IX, LP, which is the general partner of Summit Partners Growth Equity Fund IX-A, L.P. ("Fund IX-A") and Summit Partners Growth Equity Fund IX-B, L.P. ("Fund IX-B"). Summit Partners, L.P. is the managing member of Summit Partners Co-Invest Kiwi GP, LLC, which is the general partner of Summit Partners Co-Invest (Kiwi), L.P. ("Kiwi Co-Invest Fund"). Summit Master Company, LLC is the general partner of Summit Partners, L.P., which is the manager of Summit Investors Management, LLC, which is the manager of Summit Investors GE IX/VC IV, LLC ("Fund IX/VC IV") and the general partner of Summit Investors GE IX/VC IV (UK), L.P. ("Fund IX/VC IV (UK)").

F3 · ownership.nature: (continued from footnote 3) Summit Master Company, LLC, as the managing member of Summit Investors Management, LLC, has delegated voting and investment decisions with respect to the securities held by Fund IX/VC IV and Fund IX/VC IV (UK) to Summit Partners, L.P.

F4 · ownership.nature: The investment committee of Summit Partners, L.P., is currently composed of Peter Y. Chung, Scott C. Collins, and Peter L. Rottier, who may be deemed to have voting and dispositive authority over, and therefore beneficial ownership of, the reported securities. Each of the foregoing entities, Mr. Chung, Mr. Collins, and Mr. Rottier disclaims beneficial ownership of the shares, except to the extent of such person's or entity's pecuniary interest therein and the filing of this statement shall not be deemed an admission that any of the foregoing entities or persons are, for purposes of Section 16 of the Act or otherwise, the beneficial owner of any equity securities covered by this statement.

SEC source: 0000950170-24-127985 · ownership.xml · nonDerivative · entry 1

SUMMIT PARTNERS L P · CIK 0000830588 · 10% owner

Summit Partners Growth Equity Fund IX-A, L.P. · CIK 0001634415 · 10% owner

Summit Partners Growth Equity Fund IX-B, L.P. · CIK 0001634426 · 10% owner

Summit Partners Co-Invest (Kiwi), LP · CIK 0001830877 · 10% owner

SUMMIT INVESTORS GE IX/VC IV, LLC · CIK 0001654074 · 10% owner

SUMMIT INVESTORS GE IX/VC IV (UK), L.P. · CIK 0001846709 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 3,500,000

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · price: The Series B common stock, par value $0.001 per share ("Series B Common Stock"), is convertible into an equal number of shares of Series A common stock, par value $0.001 per share ("Series A Common Stock"), at any time, at the holder's election, and has no expiration date. Each share of Series B Common Stock will automatically convert into Series A Common Stock upon the earlier of (i) the date specified by 66-2/3% of the outstanding shares of Series B Common Stock, voting as a single series; (ii) following the seventh anniversary of the closing of Klaviyo, Inc.'s (the "Company") initial public offering; or (iii) any transfer, whether or not for value, except for certain permitted transfers described in the Company's certificate of incorporation.

F2 · ownership.nature: Summit Partners, L.P. is the manager of Summit Partners GE IX, LLC, which is the general partner of Summit Partners GE IX, LP, which is the general partner of Summit Partners Growth Equity Fund IX-A, L.P. ("Fund IX-A") and Summit Partners Growth Equity Fund IX-B, L.P. ("Fund IX-B"). Summit Partners, L.P. is the managing member of Summit Partners Co-Invest Kiwi GP, LLC, which is the general partner of Summit Partners Co-Invest (Kiwi), L.P. ("Kiwi Co-Invest Fund"). Summit Master Company, LLC is the general partner of Summit Partners, L.P., which is the manager of Summit Investors Management, LLC, which is the manager of Summit Investors GE IX/VC IV, LLC ("Fund IX/VC IV") and the general partner of Summit Investors GE IX/VC IV (UK), L.P. ("Fund IX/VC IV (UK)").

F3 · ownership.nature: (continued from footnote 3) Summit Master Company, LLC, as the managing member of Summit Investors Management, LLC, has delegated voting and investment decisions with respect to the securities held by Fund IX/VC IV and Fund IX/VC IV (UK) to Summit Partners, L.P.

F4 · ownership.nature: The investment committee of Summit Partners, L.P., is currently composed of Peter Y. Chung, Scott C. Collins, and Peter L. Rottier, who may be deemed to have voting and dispositive authority over, and therefore beneficial ownership of, the reported securities. Each of the foregoing entities, Mr. Chung, Mr. Collins, and Mr. Rottier disclaims beneficial ownership of the shares, except to the extent of such person's or entity's pecuniary interest therein and the filing of this statement shall not be deemed an admission that any of the foregoing entities or persons are, for purposes of Section 16 of the Act or otherwise, the beneficial owner of any equity securities covered by this statement.

SEC source: 0001104659-24-118852 · tm2428505-1_4seq1.xml · nonDerivative · entry 1

Fagnan Jeff · CIK 0001452366 · 10% owner

10b5-1 filing: No plan indicated

Ownership: Indirect · By Tailwater Investments, LLC

Disclosed balance after: 23,000

F1 · price: The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $37.0650 to $37.2000, inclusive. 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 purchased at each separate price within the range.

F2 · ownership.nature: Shares held by Tailwater Investments, LLC, an entity wholly owned by the Reporting Person. The Reporting Person disclaims beneficial ownership of the shares reported herein for purposes of Section 16 of the Securities Exchange Act of 1934, as amended ("Section 16"), except to the extent of his pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

SEC source: 0000950170-24-118371 · ownership.xml · derivative · entry 2

Shopify Strategic Holdings 3 LLC · CIK 0001993562 · 10% owner

SHOPIFY INC. · CIK 0001594805 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 14,906,816

Underlying: Series A Common Stock · 344,381 shares

Expires not disclosed

F3 · derivative.exercise_price: Each share of Series B Common Stock is convertible at any time at the option of the holder into one share of Series A Common Stock of the Issuer, and will automatically convert into Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

F3 · derivative.exercise_date: Each share of Series B Common Stock is convertible at any time at the option of the holder into one share of Series A Common Stock of the Issuer, and will automatically convert into Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

F3 · derivative.expiration_date: Each share of Series B Common Stock is convertible at any time at the option of the holder into one share of Series A Common Stock of the Issuer, and will automatically convert into Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

F2 · ownership.direct: Reflects securities held directly by Shopify Strategic Holdings 3 LLC, a wholly-owned subsidiary of Shopify Inc. ("Shopify"). Shopify is an indirect beneficial owner and disclaims beneficial ownership except to the extent of its pecuniary interest therein.

SEC source: 0000950170-24-118371 · ownership.xml · derivative · entry 1

Shopify Strategic Holdings 3 LLC · CIK 0001993562 · 10% owner

SHOPIFY INC. · CIK 0001594805 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 3,788,204

Underlying: Series B Common Stock · 344,381 shares

Expires 2032-07-28

F1 · derivative.exercise_date: 25% of the shares subject to the warrants vested on July 28, 2022, and the remaining shares vest quarterly in equal amounts through July 28, 2027. Notwithstanding the foregoing, in connection with the Issuer's initial public offering ("IPO"), 25% of the total number of shares subject to the warrants vested immediately prior to the completion of the IPO.

F2 · ownership.direct: Reflects securities held directly by Shopify Strategic Holdings 3 LLC, a wholly-owned subsidiary of Shopify Inc. ("Shopify"). Shopify is an indirect beneficial owner and disclaims beneficial ownership except to the extent of its pecuniary interest therein.

SEC source: 0001835830-24-000101 · wk-form4_1729195557.xml · derivative · entry 4

Rowland Stephen Eric · CIK 0001639368 · President

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 674,615

Underlying: Series A Common Stock · 18,114 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F2 · derivative.exercise_price: 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 shares 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.

F1 · kind: These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on March 6, 2024.

F2 · derivative.exercise_date: 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 shares 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.

F2 · derivative.expiration_date: 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 shares 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.

F6 · balance_after: Consists of (i) 58,872 shares of Series B Common Stock and (ii) 615,743 unvested RSUs awarded under the Issuer's 2015 Stock Incentive Plan, each representing the contingent right to receive one share of Series B Common Stock upon vesting and settlement.

SEC source: 0001835830-24-000101 · wk-form4_1729195557.xml · nonDerivative · entry 3

Rowland Stephen Eric · CIK 0001639368 · President

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 192,488

F1 · kind: These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on March 6, 2024.

F4 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $36.43 to $36.80 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.

F5 · balance_after: Consists of (i) 14,059 shares of Series A Common Stock and (ii) 178,429 unvested restricted stock units ("RSUs") awarded under the Issuer's 2023 Stock Option and Incentive Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement.

SEC source: 0001835830-24-000101 · wk-form4_1729195557.xml · nonDerivative · entry 2

Rowland Stephen Eric · CIK 0001639368 · President

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 194,488

F1 · kind: These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on March 6, 2024.

F3 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $36.81 to $37.80 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.

SEC source: 0001835830-24-000101 · wk-form4_1729195557.xml · nonDerivative · entry 1

Rowland Stephen Eric · CIK 0001639368 · President

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 210,602

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · kind: These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on March 6, 2024.

F2 · price: 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 shares 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.

SEC source: 0001835830-24-000099 · wk-form4_1728082822.xml · derivative · entry 3

Whalen Amanda · CIK 0001991131 · Chief Financial Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 605,118

Underlying: Series A Common Stock · 10,000 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F2 · derivative.exercise_price: 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 shares 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.

F1 · kind: These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on November 16, 2023.

F2 · derivative.exercise_date: 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 shares 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.

F2 · derivative.expiration_date: 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 shares 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.

F5 · balance_after: Consists of (i) 174,909 shares of Series B Common Stock and (ii) 430,209 unvested RSUs awarded under the Issuer's 2015 Stock Incentive Plan, each representing the contingent right to receive one share of Series B Common Stock upon vesting and settlement.

SEC source: 0001835830-24-000099 · wk-form4_1728082822.xml · nonDerivative · entry 2

Whalen Amanda · CIK 0001991131 · Chief Financial Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 422,813

F1 · kind: These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on November 16, 2023.

F3 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $34.93 to $35.63 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

F4 · balance_after: Consists of (i) 41,911 shares of Series A Common Stock and (ii) 380,902 unvested restricted stock units ("RSUs") awarded under the Issuer's 2023 Stock Option and Incentive Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement.

SEC source: 0001835830-24-000099 · wk-form4_1728082822.xml · nonDerivative · entry 1

Whalen Amanda · CIK 0001991131 · Chief Financial Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 432,813

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · kind: These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on November 16, 2023.

F2 · price: 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 shares 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.

SEC source: 0001835830-24-000095 · wk-form4_1726695677.xml · derivative · entry 8

Chaves Allen · CIK 0001991400 · Chief Technology Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 259,047

Underlying: Series A Common Stock · 32,733 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F5 · derivative.exercise_price: Each share of Series B Common Stock, par value $0.001 per share ("Series B Common Stock"), is convertible at any time at the option of the holder into one share of Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), of the Issuer, and will automatically convert into shares 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.

F5 · derivative.exercise_date: Each share of Series B Common Stock, par value $0.001 per share ("Series B Common Stock"), is convertible at any time at the option of the holder into one share of Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), of the Issuer, and will automatically convert into shares 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.

F5 · derivative.expiration_date: Each share of Series B Common Stock, par value $0.001 per share ("Series B Common Stock"), is convertible at any time at the option of the holder into one share of Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), of the Issuer, and will automatically convert into shares 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.

F6 · balance_after: Consists of (i) 178,203 shares of Series B Common Stock and (ii) 80,844 unvested restricted stock units awarded under the Issuer's 2015 Stock Incentive Plan, each representing the contingent right to receive one share of Series B Common Stock upon vesting and settlement.

SEC source: 0001835830-24-000095 · wk-form4_1726695677.xml · derivative · entry 7

Chaves Allen · CIK 0001991400 · Chief Technology Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 995,960

Underlying: Series B Common Stock · 32,733 shares

Expires 2030-04-15

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F4 · derivative.exercise_date: The shares underlying this option are fully vested and exercisable by the Reporting Person as of the date hereof.

SEC source: 0001835830-24-000094 · wk-form4_1726695553.xml · derivative · entry 3

Rowland Stephen Eric · CIK 0001639368 · President

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 692,729

Underlying: Series A Common Stock · 18,114 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F2 · derivative.exercise_price: Each share of Series B Common Stock, par value $0.001 per share ("Series B Common Stock"), is convertible at any time at the option of the holder into one share of Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), of the Issuer, and will automatically convert into shares 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.

F1 · kind: These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on March 6, 2024.

F2 · derivative.exercise_date: Each share of Series B Common Stock, par value $0.001 per share ("Series B Common Stock"), is convertible at any time at the option of the holder into one share of Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), of the Issuer, and will automatically convert into shares 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.

F2 · derivative.expiration_date: Each share of Series B Common Stock, par value $0.001 per share ("Series B Common Stock"), is convertible at any time at the option of the holder into one share of Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), of the Issuer, and will automatically convert into shares 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.

F5 · balance_after: Consists of (i) 76,986 shares of Series B Common Stock and (ii) 615,743 unvested RSUs awarded under the Issuer's 2015 Stock Incentive Plan, each representing the contingent right to receive one share of Series B Common Stock upon vesting and settlement.

SEC source: 0001835830-24-000094 · wk-form4_1726695553.xml · nonDerivative · entry 2

Rowland Stephen Eric · CIK 0001639368 · President

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 192,488

F1 · kind: These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on March 6, 2024.

F3 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $30.65 to $31.57 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.

F4 · balance_after: Consists of (i) 14,059 shares of Series A Common Stock and (ii) 178,429 unvested restricted stock units ("RSUs") awarded under the Issuer's 2023 Stock Option and Incentive Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement.

SEC source: 0001835830-24-000094 · wk-form4_1726695553.xml · nonDerivative · entry 1

Rowland Stephen Eric · CIK 0001639368 · President

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 210,602

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · kind: These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on March 6, 2024.

F2 · price: Each share of Series B Common Stock, par value $0.001 per share ("Series B Common Stock"), is convertible at any time at the option of the holder into one share of Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), of the Issuer, and will automatically convert into shares 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.

SEC source: 0001835830-24-000095 · wk-form4_1726695677.xml · derivative · entry 6

Chaves Allen · CIK 0001991400 · Chief Technology Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 226,314

Underlying: Series A Common Stock · 130,000 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F5 · derivative.exercise_price: Each share of Series B Common Stock, par value $0.001 per share ("Series B Common Stock"), is convertible at any time at the option of the holder into one share of Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), of the Issuer, and will automatically convert into shares 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.

F1 · kind: These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on November 21, 2023.

F5 · derivative.exercise_date: Each share of Series B Common Stock, par value $0.001 per share ("Series B Common Stock"), is convertible at any time at the option of the holder into one share of Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), of the Issuer, and will automatically convert into shares 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.

F5 · derivative.expiration_date: Each share of Series B Common Stock, par value $0.001 per share ("Series B Common Stock"), is convertible at any time at the option of the holder into one share of Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), of the Issuer, and will automatically convert into shares 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.

SEC source: 0001835830-24-000095 · wk-form4_1726695677.xml · derivative · entry 5

Chaves Allen · CIK 0001991400 · Chief Technology Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 356,314

Underlying: Series A Common Stock · 130,000 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F5 · derivative.exercise_price: Each share of Series B Common Stock, par value $0.001 per share ("Series B Common Stock"), is convertible at any time at the option of the holder into one share of Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), of the Issuer, and will automatically convert into shares 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.

F1 · kind: These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on November 21, 2023.

F5 · derivative.exercise_date: Each share of Series B Common Stock, par value $0.001 per share ("Series B Common Stock"), is convertible at any time at the option of the holder into one share of Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), of the Issuer, and will automatically convert into shares 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.

F5 · derivative.expiration_date: Each share of Series B Common Stock, par value $0.001 per share ("Series B Common Stock"), is convertible at any time at the option of the holder into one share of Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), of the Issuer, and will automatically convert into shares 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.

SEC source: 0001835830-24-000095 · wk-form4_1726695677.xml · derivative · entry 4

Chaves Allen · CIK 0001991400 · Chief Technology Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 1,028,693

Underlying: Series B Common Stock · 130,000 shares

Expires 2030-04-15

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · kind: These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on November 21, 2023.

F4 · derivative.exercise_date: The shares underlying this option are fully vested and exercisable by the Reporting Person as of the date hereof.

SEC source: 0001835830-24-000095 · wk-form4_1726695677.xml · nonDerivative · entry 3

Chaves Allen · CIK 0001991400 · Chief Technology Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 0

F1 · kind: These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on November 21, 2023.

F3 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $30.65 to $31.49 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

SEC source: 0001835830-24-000095 · wk-form4_1726695677.xml · nonDerivative · entry 2

Chaves Allen · CIK 0001991400 · Chief Technology Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 28,934

F1 · kind: These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on November 21, 2023.

F2 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $31.50 to $32.50 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.

SEC source: 0001835830-24-000095 · wk-form4_1726695677.xml · nonDerivative · entry 1

Chaves Allen · CIK 0001991400 · Chief Technology Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 130,000

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · kind: These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on November 21, 2023.

SEC source: 0001415889-24-023518 · form4-09172024_080927.xml · derivative · entry 3

SUMMIT PARTNERS L P · CIK 0000830588 · 10% owner

Summit Partners Growth Equity Fund IX-A, L.P. · CIK 0001634415 · 10% owner

Summit Partners Growth Equity Fund IX-B, L.P. · CIK 0001634426 · 10% owner

Summit Partners Co-Invest (Kiwi), LP · CIK 0001830877 · 10% owner

SUMMIT INVESTORS GE IX/VC IV, LLC · CIK 0001654074 · 10% owner

SUMMIT INVESTORS GE IX/VC IV (UK), L.P. · CIK 0001846709 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 46,427,778

Underlying: Series A Common Stock, par value $0.001 per share · 113,561 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: The Series B common stock, par value $0.001 per share ("Series B Common Stock"), is convertible into an equal number of shares of Series A common stock, par value $0.001 per share ("Series A Common Stock"), at any time, at the holder's election, and has no expiration date. Each share of Series B Common Stock will automatically convert into Series A Common Stock upon the earlier of (i) the date specified by 66-2/3% of the outstanding shares of Series B Common Stock, voting as a single series; (ii) following the seventh anniversary of the closing of Klaviyo, Inc.'s (the "Company") initial public offering; or (iii) any transfer, whether or not for value, except for certain permitted transfers described in the Company's certificate of incorporation. On September 13, 2024, the reporting persons directed the sale of an aggregate of 113,561 shares of their Series B Common Stock, resulting in the automatic conversion of the shares into Series A Common Stock upon execution of the sale.

F1 · derivative.exercise_date: The Series B common stock, par value $0.001 per share ("Series B Common Stock"), is convertible into an equal number of shares of Series A common stock, par value $0.001 per share ("Series A Common Stock"), at any time, at the holder's election, and has no expiration date. Each share of Series B Common Stock will automatically convert into Series A Common Stock upon the earlier of (i) the date specified by 66-2/3% of the outstanding shares of Series B Common Stock, voting as a single series; (ii) following the seventh anniversary of the closing of Klaviyo, Inc.'s (the "Company") initial public offering; or (iii) any transfer, whether or not for value, except for certain permitted transfers described in the Company's certificate of incorporation. On September 13, 2024, the reporting persons directed the sale of an aggregate of 113,561 shares of their Series B Common Stock, resulting in the automatic conversion of the shares into Series A Common Stock upon execution of the sale.

F1 · derivative.expiration_date: The Series B common stock, par value $0.001 per share ("Series B Common Stock"), is convertible into an equal number of shares of Series A common stock, par value $0.001 per share ("Series A Common Stock"), at any time, at the holder's election, and has no expiration date. Each share of Series B Common Stock will automatically convert into Series A Common Stock upon the earlier of (i) the date specified by 66-2/3% of the outstanding shares of Series B Common Stock, voting as a single series; (ii) following the seventh anniversary of the closing of Klaviyo, Inc.'s (the "Company") initial public offering; or (iii) any transfer, whether or not for value, except for certain permitted transfers described in the Company's certificate of incorporation. On September 13, 2024, the reporting persons directed the sale of an aggregate of 113,561 shares of their Series B Common Stock, resulting in the automatic conversion of the shares into Series A Common Stock upon execution of the sale.

F5 · balance_after: Consists of (i) 27,439,856 shares of Series B Common Stock held by Fund IX-A, (ii) 17,133,061 shares of Series B Common Stock held by Fund IX-B, (iii) 1,691,926 shares of Series B Common Stock held by Kiwi Co-Invest Fund, (iv) 144,217 shares of Series B Common Stock held by Fund IX/VC IV, and (v) 18,718 shares of Series B Common Stock held by Fund IX/VC IV (UK).

F2 · ownership.nature: Summit Partners, L.P. is the manager of Summit Partners GE IX, LLC, which is the general partner of Summit Partners GE IX, LP, which is the general partner of Summit Partners Growth Equity Fund IX-A, L.P. ("Fund IX-A") and Summit Partners Growth Equity Fund IX-B, L.P. ("Fund IX-B"). Summit Partners, L.P. is the managing member of Summit Partners Co-Invest Kiwi GP, LLC, which is the general partner of Summit Partners Co-Invest (Kiwi), L.P. ("Kiwi Co-Invest Fund"). Summit Master Company, LLC is the general partner of Summit Partners, L.P., which is the manager of Summit Investors Management, LLC, which is the manager of Summit Investors GE IX/VC IV, LLC ("Fund IX/VC IV") and the general partner of Summit Investors GE IX/VC IV (UK), L.P. ("Fund IX/VC IV (UK)").

F3 · ownership.nature: (continued from footnote 2) Summit Master Company, LLC, as the managing member of Summit Investors Management, LLC, has delegated voting and investment decisions with respect to the Series B Common Stock held by Fund IX/VC IV and Fund IX/VC IV (UK) to Summit Partners, L.P.

F4 · ownership.nature: The investment committee of Summit Partners, L.P., is currently composed of Peter Y. Chung, Scott C. Collins, and Peter L. Rottier, who may be deemed to have voting and dispositive authority over, and therefore beneficial ownership of, the reported securities. Each of the foregoing entities, Mr. Chung, Mr. Collins, and Mr. Rottier disclaims beneficial ownership of the shares, except to the extent of such person's or entity's pecuniary interest therein and the filing of this statement shall not be deemed an admission that any of the foregoing entities or persons are, for purposes of Section 16 of the Act or otherwise, the beneficial owner of any equity securities covered by this statement.

SEC source: 0001415889-24-023518 · form4-09172024_080927.xml · nonDerivative · entry 2

SUMMIT PARTNERS L P · CIK 0000830588 · 10% owner

Summit Partners Growth Equity Fund IX-A, L.P. · CIK 0001634415 · 10% owner

Summit Partners Growth Equity Fund IX-B, L.P. · CIK 0001634426 · 10% owner

Summit Partners Co-Invest (Kiwi), LP · CIK 0001830877 · 10% owner

SUMMIT INVESTORS GE IX/VC IV, LLC · CIK 0001654074 · 10% owner

SUMMIT INVESTORS GE IX/VC IV (UK), L.P. · CIK 0001846709 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 0

F2 · ownership.nature: Summit Partners, L.P. is the manager of Summit Partners GE IX, LLC, which is the general partner of Summit Partners GE IX, LP, which is the general partner of Summit Partners Growth Equity Fund IX-A, L.P. ("Fund IX-A") and Summit Partners Growth Equity Fund IX-B, L.P. ("Fund IX-B"). Summit Partners, L.P. is the managing member of Summit Partners Co-Invest Kiwi GP, LLC, which is the general partner of Summit Partners Co-Invest (Kiwi), L.P. ("Kiwi Co-Invest Fund"). Summit Master Company, LLC is the general partner of Summit Partners, L.P., which is the manager of Summit Investors Management, LLC, which is the manager of Summit Investors GE IX/VC IV, LLC ("Fund IX/VC IV") and the general partner of Summit Investors GE IX/VC IV (UK), L.P. ("Fund IX/VC IV (UK)").

F3 · ownership.nature: (continued from footnote 2) Summit Master Company, LLC, as the managing member of Summit Investors Management, LLC, has delegated voting and investment decisions with respect to the Series B Common Stock held by Fund IX/VC IV and Fund IX/VC IV (UK) to Summit Partners, L.P.

F4 · ownership.nature: The investment committee of Summit Partners, L.P., is currently composed of Peter Y. Chung, Scott C. Collins, and Peter L. Rottier, who may be deemed to have voting and dispositive authority over, and therefore beneficial ownership of, the reported securities. Each of the foregoing entities, Mr. Chung, Mr. Collins, and Mr. Rottier disclaims beneficial ownership of the shares, except to the extent of such person's or entity's pecuniary interest therein and the filing of this statement shall not be deemed an admission that any of the foregoing entities or persons are, for purposes of Section 16 of the Act or otherwise, the beneficial owner of any equity securities covered by this statement.

SEC source: 0001415889-24-023518 · form4-09172024_080927.xml · nonDerivative · entry 1

SUMMIT PARTNERS L P · CIK 0000830588 · 10% owner

Summit Partners Growth Equity Fund IX-A, L.P. · CIK 0001634415 · 10% owner

Summit Partners Growth Equity Fund IX-B, L.P. · CIK 0001634426 · 10% owner

Summit Partners Co-Invest (Kiwi), LP · CIK 0001830877 · 10% owner

SUMMIT INVESTORS GE IX/VC IV, LLC · CIK 0001654074 · 10% owner

SUMMIT INVESTORS GE IX/VC IV (UK), L.P. · CIK 0001846709 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 113,561

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · price: The Series B common stock, par value $0.001 per share ("Series B Common Stock"), is convertible into an equal number of shares of Series A common stock, par value $0.001 per share ("Series A Common Stock"), at any time, at the holder's election, and has no expiration date. Each share of Series B Common Stock will automatically convert into Series A Common Stock upon the earlier of (i) the date specified by 66-2/3% of the outstanding shares of Series B Common Stock, voting as a single series; (ii) following the seventh anniversary of the closing of Klaviyo, Inc.'s (the "Company") initial public offering; or (iii) any transfer, whether or not for value, except for certain permitted transfers described in the Company's certificate of incorporation. On September 13, 2024, the reporting persons directed the sale of an aggregate of 113,561 shares of their Series B Common Stock, resulting in the automatic conversion of the shares into Series A Common Stock upon execution of the sale.

F2 · ownership.nature: Summit Partners, L.P. is the manager of Summit Partners GE IX, LLC, which is the general partner of Summit Partners GE IX, LP, which is the general partner of Summit Partners Growth Equity Fund IX-A, L.P. ("Fund IX-A") and Summit Partners Growth Equity Fund IX-B, L.P. ("Fund IX-B"). Summit Partners, L.P. is the managing member of Summit Partners Co-Invest Kiwi GP, LLC, which is the general partner of Summit Partners Co-Invest (Kiwi), L.P. ("Kiwi Co-Invest Fund"). Summit Master Company, LLC is the general partner of Summit Partners, L.P., which is the manager of Summit Investors Management, LLC, which is the manager of Summit Investors GE IX/VC IV, LLC ("Fund IX/VC IV") and the general partner of Summit Investors GE IX/VC IV (UK), L.P. ("Fund IX/VC IV (UK)").

F3 · ownership.nature: (continued from footnote 2) Summit Master Company, LLC, as the managing member of Summit Investors Management, LLC, has delegated voting and investment decisions with respect to the Series B Common Stock held by Fund IX/VC IV and Fund IX/VC IV (UK) to Summit Partners, L.P.

F4 · ownership.nature: The investment committee of Summit Partners, L.P., is currently composed of Peter Y. Chung, Scott C. Collins, and Peter L. Rottier, who may be deemed to have voting and dispositive authority over, and therefore beneficial ownership of, the reported securities. Each of the foregoing entities, Mr. Chung, Mr. Collins, and Mr. Rottier disclaims beneficial ownership of the shares, except to the extent of such person's or entity's pecuniary interest therein and the filing of this statement shall not be deemed an admission that any of the foregoing entities or persons are, for purposes of Section 16 of the Act or otherwise, the beneficial owner of any equity securities covered by this statement.

SEC source: 0001415889-24-023447 · form4-09162024_090941.xml · derivative · entry 3

SUMMIT PARTNERS L P · CIK 0000830588 · 10% owner

Summit Partners Growth Equity Fund IX-A, L.P. · CIK 0001634415 · 10% owner

Summit Partners Growth Equity Fund IX-B, L.P. · CIK 0001634426 · 10% owner

Summit Partners Co-Invest (Kiwi), LP · CIK 0001830877 · 10% owner

SUMMIT INVESTORS GE IX/VC IV, LLC · CIK 0001654074 · 10% owner

SUMMIT INVESTORS GE IX/VC IV (UK), L.P. · CIK 0001846709 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 46,541,339

Underlying: Series A Common Stock, par value $0.001 per share · 107,205 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: The Series B common stock, par value $0.001 per share ("Series B Common Stock"), is convertible into an equal number of shares of Series A common stock, par value $0.001 per share ("Series A Common Stock"), at any time, at the holder's election, and has no expiration date. Each share of Series B Common Stock will automatically convert into Series A Common Stock upon the earlier of (i) the date specified by 66-2/3% of the outstanding shares of Series B Common Stock, voting as a single series; (ii) following the seventh anniversary of the closing of Klaviyo, Inc.'s (the "Company") initial public offering; or (iii) any transfer, whether or not for value, except for certain permitted transfers described in the Company's certificate of incorporation. On September 12, 2024, the reporting persons directed the sale of an aggregate of 107,205 shares of their Series B Common Stock, resulting in the automatic conversion of the shares into Series A Common Stock upon execution of the sale.

F1 · derivative.exercise_date: The Series B common stock, par value $0.001 per share ("Series B Common Stock"), is convertible into an equal number of shares of Series A common stock, par value $0.001 per share ("Series A Common Stock"), at any time, at the holder's election, and has no expiration date. Each share of Series B Common Stock will automatically convert into Series A Common Stock upon the earlier of (i) the date specified by 66-2/3% of the outstanding shares of Series B Common Stock, voting as a single series; (ii) following the seventh anniversary of the closing of Klaviyo, Inc.'s (the "Company") initial public offering; or (iii) any transfer, whether or not for value, except for certain permitted transfers described in the Company's certificate of incorporation. On September 12, 2024, the reporting persons directed the sale of an aggregate of 107,205 shares of their Series B Common Stock, resulting in the automatic conversion of the shares into Series A Common Stock upon execution of the sale.

F1 · derivative.expiration_date: The Series B common stock, par value $0.001 per share ("Series B Common Stock"), is convertible into an equal number of shares of Series A common stock, par value $0.001 per share ("Series A Common Stock"), at any time, at the holder's election, and has no expiration date. Each share of Series B Common Stock will automatically convert into Series A Common Stock upon the earlier of (i) the date specified by 66-2/3% of the outstanding shares of Series B Common Stock, voting as a single series; (ii) following the seventh anniversary of the closing of Klaviyo, Inc.'s (the "Company") initial public offering; or (iii) any transfer, whether or not for value, except for certain permitted transfers described in the Company's certificate of incorporation. On September 12, 2024, the reporting persons directed the sale of an aggregate of 107,205 shares of their Series B Common Stock, resulting in the automatic conversion of the shares into Series A Common Stock upon execution of the sale.

F5 · balance_after: Consists of (i) 27,506,973 shares of Series B Common Stock held by Fund IX-A, (ii) 17,174,968 shares of Series B Common Stock held by Fund IX-B, (iii) 1,696,064 shares of Series B Common Stock held by Kiwi Co-Invest Fund, (iv) 144,570 shares of Series B Common Stock held by Fund IX/VC IV, and (v) 18,764 shares of Series B Common Stock held by Fund IX/VC IV (UK).

F2 · ownership.nature: Summit Partners, L.P. is the manager of Summit Partners GE IX, LLC, which is the general partner of Summit Partners GE IX, LP, which is the general partner of Summit Partners Growth Equity Fund IX-A, L.P. ("Fund IX-A") and Summit Partners Growth Equity Fund IX-B, L.P. ("Fund IX-B"). Summit Partners, L.P. is the managing member of Summit Partners Co-Invest Kiwi GP, LLC, which is the general partner of Summit Partners Co-Invest (Kiwi), L.P. ("Kiwi Co-Invest Fund"). Summit Master Company, LLC is the general partner of Summit Partners, L.P., which is the manager of Summit Investors Management, LLC, which is the manager of Summit Investors GE IX/VC IV, LLC ("Fund IX/VC IV") and the general partner of Summit Investors GE IX/VC IV (UK), L.P. ("Fund IX/VC IV (UK)").

F3 · ownership.nature: (continued from footnote 2) Summit Master Company, LLC, as the managing member of Summit Investors Management, LLC, has delegated voting and investment decisions with respect to the Series B Common Stock held by Fund IX/VC IV and Fund IX/VC IV (UK) to Summit Partners, L.P.

F4 · ownership.nature: The investment committee of Summit Partners, L.P., is currently composed of Peter Y. Chung, Scott C. Collins, and Peter L. Rottier, who may be deemed to have voting and dispositive authority over, and therefore beneficial ownership of, the reported securities. Each of the foregoing entities, Mr. Chung, Mr. Collins, and Mr. Rottier disclaims beneficial ownership of the shares, except to the extent of such person's or entity's pecuniary interest therein and the filing of this statement shall not be deemed an admission that any of the foregoing entities or persons are, for purposes of Section 16 of the Act or otherwise, the beneficial owner of any equity securities covered by this statement.

SEC source: 0001415889-24-023447 · form4-09162024_090941.xml · nonDerivative · entry 2

SUMMIT PARTNERS L P · CIK 0000830588 · 10% owner

Summit Partners Growth Equity Fund IX-A, L.P. · CIK 0001634415 · 10% owner

Summit Partners Growth Equity Fund IX-B, L.P. · CIK 0001634426 · 10% owner

Summit Partners Co-Invest (Kiwi), LP · CIK 0001830877 · 10% owner

SUMMIT INVESTORS GE IX/VC IV, LLC · CIK 0001654074 · 10% owner

SUMMIT INVESTORS GE IX/VC IV (UK), L.P. · CIK 0001846709 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 0

F2 · ownership.nature: Summit Partners, L.P. is the manager of Summit Partners GE IX, LLC, which is the general partner of Summit Partners GE IX, LP, which is the general partner of Summit Partners Growth Equity Fund IX-A, L.P. ("Fund IX-A") and Summit Partners Growth Equity Fund IX-B, L.P. ("Fund IX-B"). Summit Partners, L.P. is the managing member of Summit Partners Co-Invest Kiwi GP, LLC, which is the general partner of Summit Partners Co-Invest (Kiwi), L.P. ("Kiwi Co-Invest Fund"). Summit Master Company, LLC is the general partner of Summit Partners, L.P., which is the manager of Summit Investors Management, LLC, which is the manager of Summit Investors GE IX/VC IV, LLC ("Fund IX/VC IV") and the general partner of Summit Investors GE IX/VC IV (UK), L.P. ("Fund IX/VC IV (UK)").

F3 · ownership.nature: (continued from footnote 2) Summit Master Company, LLC, as the managing member of Summit Investors Management, LLC, has delegated voting and investment decisions with respect to the Series B Common Stock held by Fund IX/VC IV and Fund IX/VC IV (UK) to Summit Partners, L.P.

F4 · ownership.nature: The investment committee of Summit Partners, L.P., is currently composed of Peter Y. Chung, Scott C. Collins, and Peter L. Rottier, who may be deemed to have voting and dispositive authority over, and therefore beneficial ownership of, the reported securities. Each of the foregoing entities, Mr. Chung, Mr. Collins, and Mr. Rottier disclaims beneficial ownership of the shares, except to the extent of such person's or entity's pecuniary interest therein and the filing of this statement shall not be deemed an admission that any of the foregoing entities or persons are, for purposes of Section 16 of the Act or otherwise, the beneficial owner of any equity securities covered by this statement.

SEC source: 0001415889-24-023447 · form4-09162024_090941.xml · nonDerivative · entry 1

SUMMIT PARTNERS L P · CIK 0000830588 · 10% owner

Summit Partners Growth Equity Fund IX-A, L.P. · CIK 0001634415 · 10% owner

Summit Partners Growth Equity Fund IX-B, L.P. · CIK 0001634426 · 10% owner

Summit Partners Co-Invest (Kiwi), LP · CIK 0001830877 · 10% owner

SUMMIT INVESTORS GE IX/VC IV, LLC · CIK 0001654074 · 10% owner

SUMMIT INVESTORS GE IX/VC IV (UK), L.P. · CIK 0001846709 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 107,205

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · price: The Series B common stock, par value $0.001 per share ("Series B Common Stock"), is convertible into an equal number of shares of Series A common stock, par value $0.001 per share ("Series A Common Stock"), at any time, at the holder's election, and has no expiration date. Each share of Series B Common Stock will automatically convert into Series A Common Stock upon the earlier of (i) the date specified by 66-2/3% of the outstanding shares of Series B Common Stock, voting as a single series; (ii) following the seventh anniversary of the closing of Klaviyo, Inc.'s (the "Company") initial public offering; or (iii) any transfer, whether or not for value, except for certain permitted transfers described in the Company's certificate of incorporation. On September 12, 2024, the reporting persons directed the sale of an aggregate of 107,205 shares of their Series B Common Stock, resulting in the automatic conversion of the shares into Series A Common Stock upon execution of the sale.

F2 · ownership.nature: Summit Partners, L.P. is the manager of Summit Partners GE IX, LLC, which is the general partner of Summit Partners GE IX, LP, which is the general partner of Summit Partners Growth Equity Fund IX-A, L.P. ("Fund IX-A") and Summit Partners Growth Equity Fund IX-B, L.P. ("Fund IX-B"). Summit Partners, L.P. is the managing member of Summit Partners Co-Invest Kiwi GP, LLC, which is the general partner of Summit Partners Co-Invest (Kiwi), L.P. ("Kiwi Co-Invest Fund"). Summit Master Company, LLC is the general partner of Summit Partners, L.P., which is the manager of Summit Investors Management, LLC, which is the manager of Summit Investors GE IX/VC IV, LLC ("Fund IX/VC IV") and the general partner of Summit Investors GE IX/VC IV (UK), L.P. ("Fund IX/VC IV (UK)").

F3 · ownership.nature: (continued from footnote 2) Summit Master Company, LLC, as the managing member of Summit Investors Management, LLC, has delegated voting and investment decisions with respect to the Series B Common Stock held by Fund IX/VC IV and Fund IX/VC IV (UK) to Summit Partners, L.P.

F4 · ownership.nature: The investment committee of Summit Partners, L.P., is currently composed of Peter Y. Chung, Scott C. Collins, and Peter L. Rottier, who may be deemed to have voting and dispositive authority over, and therefore beneficial ownership of, the reported securities. Each of the foregoing entities, Mr. Chung, Mr. Collins, and Mr. Rottier disclaims beneficial ownership of the shares, except to the extent of such person's or entity's pecuniary interest therein and the filing of this statement shall not be deemed an admission that any of the foregoing entities or persons are, for purposes of Section 16 of the Act or otherwise, the beneficial owner of any equity securities covered by this statement.

SEC source: 0001415889-24-023354 · form4-09132024_080920.xml · derivative · entry 3

SUMMIT PARTNERS L P · CIK 0000830588 · 10% owner

Summit Partners Growth Equity Fund IX-A, L.P. · CIK 0001634415 · 10% owner

Summit Partners Growth Equity Fund IX-B, L.P. · CIK 0001634426 · 10% owner

Summit Partners Co-Invest (Kiwi), LP · CIK 0001830877 · 10% owner

SUMMIT INVESTORS GE IX/VC IV, LLC · CIK 0001654074 · 10% owner

SUMMIT INVESTORS GE IX/VC IV (UK), L.P. · CIK 0001846709 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 46,648,544

Underlying: Series A Common Stock, par value $0.001 per share · 2,942 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: The Series B common stock, par value $0.001 per share ("Series B Common Stock"), is convertible into an equal number of shares of Series A common stock, par value $0.001 per share ("Series A Common Stock"), at any time, at the holder's election, and has no expiration date. Each share of Series B Common Stock will automatically convert into Series A Common Stock upon the earlier of (i) the date specified by 66-2/3% of the outstanding shares of Series B Common Stock, voting as a single series; (ii) following the seventh anniversary of the closing of Klaviyo, Inc.'s (the "Company") initial public offering; or (iii) any transfer, whether or not for value, except for certain permitted transfers described in the Company's certificate of incorporation. On September 11, 2024, the reporting persons directed the sale of an aggregate of 2,942 shares of their Series B Common Stock, resulting in the automatic conversion of the shares into Series A Common Stock upon execution of the sale.

F1 · derivative.exercise_date: The Series B common stock, par value $0.001 per share ("Series B Common Stock"), is convertible into an equal number of shares of Series A common stock, par value $0.001 per share ("Series A Common Stock"), at any time, at the holder's election, and has no expiration date. Each share of Series B Common Stock will automatically convert into Series A Common Stock upon the earlier of (i) the date specified by 66-2/3% of the outstanding shares of Series B Common Stock, voting as a single series; (ii) following the seventh anniversary of the closing of Klaviyo, Inc.'s (the "Company") initial public offering; or (iii) any transfer, whether or not for value, except for certain permitted transfers described in the Company's certificate of incorporation. On September 11, 2024, the reporting persons directed the sale of an aggregate of 2,942 shares of their Series B Common Stock, resulting in the automatic conversion of the shares into Series A Common Stock upon execution of the sale.

F1 · derivative.expiration_date: The Series B common stock, par value $0.001 per share ("Series B Common Stock"), is convertible into an equal number of shares of Series A common stock, par value $0.001 per share ("Series A Common Stock"), at any time, at the holder's election, and has no expiration date. Each share of Series B Common Stock will automatically convert into Series A Common Stock upon the earlier of (i) the date specified by 66-2/3% of the outstanding shares of Series B Common Stock, voting as a single series; (ii) following the seventh anniversary of the closing of Klaviyo, Inc.'s (the "Company") initial public offering; or (iii) any transfer, whether or not for value, except for certain permitted transfers described in the Company's certificate of incorporation. On September 11, 2024, the reporting persons directed the sale of an aggregate of 2,942 shares of their Series B Common Stock, resulting in the automatic conversion of the shares into Series A Common Stock upon execution of the sale.

F5 · balance_after: Consists of (i) 27,570,334 shares of Series B Common Stock held by Fund IX-A, (ii) 17,214,529 shares of Series B Common Stock held by Fund IX-B, (iii) 1,699,971 shares of Series B Common Stock held by Kiwi Co-Invest Fund, (iv) 144,903 shares of Series B Common Stock held by Fund IX/VC IV, and (v) 18,807 shares of Series B Common Stock held by Fund IX/VC IV (UK).

F2 · ownership.nature: Summit Partners, L.P. is the manager of Summit Partners GE IX, LLC, which is the general partner of Summit Partners GE IX, LP, which is the general partner of Summit Partners Growth Equity Fund IX-A, L.P. ("Fund IX-A") and Summit Partners Growth Equity Fund IX-B, L.P. ("Fund IX-B"). Summit Partners, L.P. is the managing member of Summit Partners Co-Invest Kiwi GP, LLC, which is the general partner of Summit Partners Co-Invest (Kiwi), L.P. ("Kiwi Co-Invest Fund"). Summit Master Company, LLC is the general partner of Summit Partners, L.P., which is the manager of Summit Investors Management, LLC, which is the manager of Summit Investors GE IX/VC IV, LLC ("Fund IX/VC IV") and the general partner of Summit Investors GE IX/VC IV (UK), L.P. ("Fund IX/VC IV (UK)").

F3 · ownership.nature: (continued from footnote 2) Summit Master Company, LLC, as the managing member of Summit Investors Management, LLC, has delegated voting and investment decisions with respect to the Series B Common Stock held by Fund IX/VC IV and Fund IX/VC IV (UK) to Summit Partners, L.P.

F4 · ownership.nature: The investment committee of Summit Partners, L.P., is currently composed of Peter Y. Chung, Scott C. Collins, and Peter L. Rottier, who may be deemed to have voting and dispositive authority over, and therefore beneficial ownership of, the reported securities. Each of the foregoing entities, Mr. Chung, Mr. Collins, and Mr. Rottier disclaims beneficial ownership of the shares, except to the extent of such person's or entity's pecuniary interest therein and the filing of this statement shall not be deemed an admission that any of the foregoing entities or persons are, for purposes of Section 16 of the Act or otherwise, the beneficial owner of any equity securities covered by this statement.

SEC source: 0001415889-24-023354 · form4-09132024_080920.xml · nonDerivative · entry 2

SUMMIT PARTNERS L P · CIK 0000830588 · 10% owner

Summit Partners Growth Equity Fund IX-A, L.P. · CIK 0001634415 · 10% owner

Summit Partners Growth Equity Fund IX-B, L.P. · CIK 0001634426 · 10% owner

Summit Partners Co-Invest (Kiwi), LP · CIK 0001830877 · 10% owner

SUMMIT INVESTORS GE IX/VC IV, LLC · CIK 0001654074 · 10% owner

SUMMIT INVESTORS GE IX/VC IV (UK), L.P. · CIK 0001846709 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 0

F2 · ownership.nature: Summit Partners, L.P. is the manager of Summit Partners GE IX, LLC, which is the general partner of Summit Partners GE IX, LP, which is the general partner of Summit Partners Growth Equity Fund IX-A, L.P. ("Fund IX-A") and Summit Partners Growth Equity Fund IX-B, L.P. ("Fund IX-B"). Summit Partners, L.P. is the managing member of Summit Partners Co-Invest Kiwi GP, LLC, which is the general partner of Summit Partners Co-Invest (Kiwi), L.P. ("Kiwi Co-Invest Fund"). Summit Master Company, LLC is the general partner of Summit Partners, L.P., which is the manager of Summit Investors Management, LLC, which is the manager of Summit Investors GE IX/VC IV, LLC ("Fund IX/VC IV") and the general partner of Summit Investors GE IX/VC IV (UK), L.P. ("Fund IX/VC IV (UK)").

F3 · ownership.nature: (continued from footnote 2) Summit Master Company, LLC, as the managing member of Summit Investors Management, LLC, has delegated voting and investment decisions with respect to the Series B Common Stock held by Fund IX/VC IV and Fund IX/VC IV (UK) to Summit Partners, L.P.

F4 · ownership.nature: The investment committee of Summit Partners, L.P., is currently composed of Peter Y. Chung, Scott C. Collins, and Peter L. Rottier, who may be deemed to have voting and dispositive authority over, and therefore beneficial ownership of, the reported securities. Each of the foregoing entities, Mr. Chung, Mr. Collins, and Mr. Rottier disclaims beneficial ownership of the shares, except to the extent of such person's or entity's pecuniary interest therein and the filing of this statement shall not be deemed an admission that any of the foregoing entities or persons are, for purposes of Section 16 of the Act or otherwise, the beneficial owner of any equity securities covered by this statement.

SEC source: 0001415889-24-023354 · form4-09132024_080920.xml · nonDerivative · entry 1

SUMMIT PARTNERS L P · CIK 0000830588 · 10% owner

Summit Partners Growth Equity Fund IX-A, L.P. · CIK 0001634415 · 10% owner

Summit Partners Growth Equity Fund IX-B, L.P. · CIK 0001634426 · 10% owner

Summit Partners Co-Invest (Kiwi), LP · CIK 0001830877 · 10% owner

SUMMIT INVESTORS GE IX/VC IV, LLC · CIK 0001654074 · 10% owner

SUMMIT INVESTORS GE IX/VC IV (UK), L.P. · CIK 0001846709 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 2,942

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · price: The Series B common stock, par value $0.001 per share ("Series B Common Stock"), is convertible into an equal number of shares of Series A common stock, par value $0.001 per share ("Series A Common Stock"), at any time, at the holder's election, and has no expiration date. Each share of Series B Common Stock will automatically convert into Series A Common Stock upon the earlier of (i) the date specified by 66-2/3% of the outstanding shares of Series B Common Stock, voting as a single series; (ii) following the seventh anniversary of the closing of Klaviyo, Inc.'s (the "Company") initial public offering; or (iii) any transfer, whether or not for value, except for certain permitted transfers described in the Company's certificate of incorporation. On September 11, 2024, the reporting persons directed the sale of an aggregate of 2,942 shares of their Series B Common Stock, resulting in the automatic conversion of the shares into Series A Common Stock upon execution of the sale.

F2 · ownership.nature: Summit Partners, L.P. is the manager of Summit Partners GE IX, LLC, which is the general partner of Summit Partners GE IX, LP, which is the general partner of Summit Partners Growth Equity Fund IX-A, L.P. ("Fund IX-A") and Summit Partners Growth Equity Fund IX-B, L.P. ("Fund IX-B"). Summit Partners, L.P. is the managing member of Summit Partners Co-Invest Kiwi GP, LLC, which is the general partner of Summit Partners Co-Invest (Kiwi), L.P. ("Kiwi Co-Invest Fund"). Summit Master Company, LLC is the general partner of Summit Partners, L.P., which is the manager of Summit Investors Management, LLC, which is the manager of Summit Investors GE IX/VC IV, LLC ("Fund IX/VC IV") and the general partner of Summit Investors GE IX/VC IV (UK), L.P. ("Fund IX/VC IV (UK)").

F3 · ownership.nature: (continued from footnote 2) Summit Master Company, LLC, as the managing member of Summit Investors Management, LLC, has delegated voting and investment decisions with respect to the Series B Common Stock held by Fund IX/VC IV and Fund IX/VC IV (UK) to Summit Partners, L.P.

F4 · ownership.nature: The investment committee of Summit Partners, L.P., is currently composed of Peter Y. Chung, Scott C. Collins, and Peter L. Rottier, who may be deemed to have voting and dispositive authority over, and therefore beneficial ownership of, the reported securities. Each of the foregoing entities, Mr. Chung, Mr. Collins, and Mr. Rottier disclaims beneficial ownership of the shares, except to the extent of such person's or entity's pecuniary interest therein and the filing of this statement shall not be deemed an admission that any of the foregoing entities or persons are, for purposes of Section 16 of the Act or otherwise, the beneficial owner of any equity securities covered by this statement.

SEC source: 0001835830-24-000093 · wk-form4_1725668000.xml · derivative · entry 4

Whalen Amanda · CIK 0001991131 · Chief Financial Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 615,118

Underlying: Series A Common Stock · 10,000 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F2 · derivative.exercise_price: Each share of Series B Common Stock, par value $0.001 per share ("Series B Common Stock"), is convertible at any time at the option of the holder into one share of Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), of the Issuer, and will automatically convert into shares 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.

F1 · kind: These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on November 16, 2023.

F2 · derivative.exercise_date: Each share of Series B Common Stock, par value $0.001 per share ("Series B Common Stock"), is convertible at any time at the option of the holder into one share of Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), of the Issuer, and will automatically convert into shares 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.

F2 · derivative.expiration_date: Each share of Series B Common Stock, par value $0.001 per share ("Series B Common Stock"), is convertible at any time at the option of the holder into one share of Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), of the Issuer, and will automatically convert into shares 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.

F6 · balance_after: Consists of (i) 184,909 shares of Series B Common Stock and (ii) 430,209 unvested RSUs awarded under the Issuer's 2015 Stock Incentive Plan, each representing the contingent right to receive one share of Series B Common Stock upon vesting and settlement.

SEC source: 0001835830-24-000093 · wk-form4_1725668000.xml · nonDerivative · entry 3

Whalen Amanda · CIK 0001991131 · Chief Financial Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 422,813

F1 · kind: These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on November 16, 2023.

F4 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $29.35 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.

F5 · balance_after: Consists of (i) 41,911 shares of Series A Common Stock and (ii) 380,902 unvested restricted stock units ("RSUs") awarded under the Issuer's 2023 Stock Option and Incentive Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement.

SEC source: 0001835830-24-000093 · wk-form4_1725668000.xml · nonDerivative · entry 2

Whalen Amanda · CIK 0001991131 · Chief Financial Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 423,013

F1 · kind: These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on November 16, 2023.

F3 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $29.47 to $30.46 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.

SEC source: 0001835830-24-000093 · wk-form4_1725668000.xml · nonDerivative · entry 1

Whalen Amanda · CIK 0001991131 · Chief Financial Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 432,813

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · kind: These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on November 16, 2023.

F2 · price: Each share of Series B Common Stock, par value $0.001 per share ("Series B Common Stock"), is convertible at any time at the option of the holder into one share of Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), of the Issuer, and will automatically convert into shares 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.

SEC source: 0001415889-24-022891 · form4-09052024_080933.xml · derivative · entry 3

SUMMIT PARTNERS L P · CIK 0000830588 · 10% owner

Summit Partners Growth Equity Fund IX-A, L.P. · CIK 0001634415 · 10% owner

Summit Partners Growth Equity Fund IX-B, L.P. · CIK 0001634426 · 10% owner

Summit Partners Co-Invest (Kiwi), LP · CIK 0001830877 · 10% owner

SUMMIT INVESTORS GE IX/VC IV, LLC · CIK 0001654074 · 10% owner

SUMMIT INVESTORS GE IX/VC IV (UK), L.P. · CIK 0001846709 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 46,651,486

Underlying: Series A Common Stock, par value $0.001 per share · 6,039 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: The Series B common stock, par value $0.001 per share ("Series B Common Stock"), is convertible into an equal number of shares of Series A common stock, par value $0.001 per share ("Series A Common Stock"), at any time, at the holder's election, and has no expiration date. Each share of Series B Common Stock will automatically convert into Series A Common Stock upon the earlier of (i) the date specified by 66-2/3% of the outstanding shares of Series B Common Stock, voting as a single series; (ii) following the seventh anniversary of the closing of Klaviyo, Inc.'s (the "Company") initial public offering; or (iii) any transfer, whether or not for value, except for certain permitted transfers described in the Company's certificate of incorporation. On September 3, 2024, the reporting persons directed the sale of an aggregate of 6,039 shares of their Series B Common Stock, resulting in the automatic conversion of the shares into Series A Common Stock upon execution of the sale.

F1 · derivative.exercise_date: The Series B common stock, par value $0.001 per share ("Series B Common Stock"), is convertible into an equal number of shares of Series A common stock, par value $0.001 per share ("Series A Common Stock"), at any time, at the holder's election, and has no expiration date. Each share of Series B Common Stock will automatically convert into Series A Common Stock upon the earlier of (i) the date specified by 66-2/3% of the outstanding shares of Series B Common Stock, voting as a single series; (ii) following the seventh anniversary of the closing of Klaviyo, Inc.'s (the "Company") initial public offering; or (iii) any transfer, whether or not for value, except for certain permitted transfers described in the Company's certificate of incorporation. On September 3, 2024, the reporting persons directed the sale of an aggregate of 6,039 shares of their Series B Common Stock, resulting in the automatic conversion of the shares into Series A Common Stock upon execution of the sale.

F1 · derivative.expiration_date: The Series B common stock, par value $0.001 per share ("Series B Common Stock"), is convertible into an equal number of shares of Series A common stock, par value $0.001 per share ("Series A Common Stock"), at any time, at the holder's election, and has no expiration date. Each share of Series B Common Stock will automatically convert into Series A Common Stock upon the earlier of (i) the date specified by 66-2/3% of the outstanding shares of Series B Common Stock, voting as a single series; (ii) following the seventh anniversary of the closing of Klaviyo, Inc.'s (the "Company") initial public offering; or (iii) any transfer, whether or not for value, except for certain permitted transfers described in the Company's certificate of incorporation. On September 3, 2024, the reporting persons directed the sale of an aggregate of 6,039 shares of their Series B Common Stock, resulting in the automatic conversion of the shares into Series A Common Stock upon execution of the sale.

F5 · balance_after: Consists of (i) 27,572,073 shares of Series B Common Stock held by Fund IX-A, (ii) 17,215,614 shares of Series B Common Stock held by Fund IX-B, (iii) 1,700,078 shares of Series B Common Stock held by Kiwi Co-Invest Fund, (iv) 144,912 shares of Series B Common Stock held by Fund IX/VC IV, and (v) 18,809 shares of Series B Common Stock held by Fund IX/VC IV (UK).

F2 · ownership.nature: Summit Partners, L.P. is the manager of Summit Partners GE IX, LLC, which is the general partner of Summit Partners GE IX, LP, which is the general partner of Summit Partners Growth Equity Fund IX-A, L.P. ("Fund IX-A") and Summit Partners Growth Equity Fund IX-B, L.P. ("Fund IX-B"). Summit Partners, L.P. is the managing member of Summit Partners Co-Invest Kiwi GP, LLC, which is the general partner of Summit Partners Co-Invest (Kiwi), L.P. ("Kiwi Co-Invest Fund"). Summit Master Company, LLC is the general partner of Summit Partners, L.P., which is the manager of Summit Investors Management, LLC, which is the manager of Summit Investors GE IX/VC IV, LLC ("Fund IX/VC IV") and the general partner of Summit Investors GE IX/VC IV (UK), L.P. ("Fund IX/VC IV (UK)").

F3 · ownership.nature: (continued from footnote 2) Summit Master Company, LLC, as the managing member of Summit Investors Management, LLC, has delegated voting and investment decisions with respect to the Series B Common Stock held by Fund IX/VC IV and Fund IX/VC IV (UK) to Summit Partners, L.P.

F4 · ownership.nature: The investment committee of Summit Partners, L.P., is currently composed of Peter Y. Chung, Scott C. Collins, and Peter L. Rottier, who may be deemed to have voting and dispositive authority over, and therefore beneficial ownership of, the reported securities. Each of the foregoing entities, Mr. Chung, Mr. Collins, and Mr. Rottier disclaims beneficial ownership of the shares, except to the extent of such person's or entity's pecuniary interest therein and the filing of this statement shall not be deemed an admission that any of the foregoing entities or persons are, for purposes of Section 16 of the Act or otherwise, the beneficial owner of any equity securities covered by this statement.

SEC source: 0001415889-24-022891 · form4-09052024_080933.xml · nonDerivative · entry 2

SUMMIT PARTNERS L P · CIK 0000830588 · 10% owner

Summit Partners Growth Equity Fund IX-A, L.P. · CIK 0001634415 · 10% owner

Summit Partners Growth Equity Fund IX-B, L.P. · CIK 0001634426 · 10% owner

Summit Partners Co-Invest (Kiwi), LP · CIK 0001830877 · 10% owner

SUMMIT INVESTORS GE IX/VC IV, LLC · CIK 0001654074 · 10% owner

SUMMIT INVESTORS GE IX/VC IV (UK), L.P. · CIK 0001846709 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 0

F2 · ownership.nature: Summit Partners, L.P. is the manager of Summit Partners GE IX, LLC, which is the general partner of Summit Partners GE IX, LP, which is the general partner of Summit Partners Growth Equity Fund IX-A, L.P. ("Fund IX-A") and Summit Partners Growth Equity Fund IX-B, L.P. ("Fund IX-B"). Summit Partners, L.P. is the managing member of Summit Partners Co-Invest Kiwi GP, LLC, which is the general partner of Summit Partners Co-Invest (Kiwi), L.P. ("Kiwi Co-Invest Fund"). Summit Master Company, LLC is the general partner of Summit Partners, L.P., which is the manager of Summit Investors Management, LLC, which is the manager of Summit Investors GE IX/VC IV, LLC ("Fund IX/VC IV") and the general partner of Summit Investors GE IX/VC IV (UK), L.P. ("Fund IX/VC IV (UK)").

F3 · ownership.nature: (continued from footnote 2) Summit Master Company, LLC, as the managing member of Summit Investors Management, LLC, has delegated voting and investment decisions with respect to the Series B Common Stock held by Fund IX/VC IV and Fund IX/VC IV (UK) to Summit Partners, L.P.

F4 · ownership.nature: The investment committee of Summit Partners, L.P., is currently composed of Peter Y. Chung, Scott C. Collins, and Peter L. Rottier, who may be deemed to have voting and dispositive authority over, and therefore beneficial ownership of, the reported securities. Each of the foregoing entities, Mr. Chung, Mr. Collins, and Mr. Rottier disclaims beneficial ownership of the shares, except to the extent of such person's or entity's pecuniary interest therein and the filing of this statement shall not be deemed an admission that any of the foregoing entities or persons are, for purposes of Section 16 of the Act or otherwise, the beneficial owner of any equity securities covered by this statement.