KVYO

SEC source: 0001470831-25-000141 · wk-form4_1755650948.xml · nonDerivative · entry 1

Galvin Carmel · CIK 0001733091 · Chief People Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 686,988

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").

SEC source: 0001470831-25-000143 · wk-form4_1755651158.xml · derivative · entry 3

Fernandez Gomez Luciano · CIK 0001730978 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 56,000

Underlying: Series A Common Stock · 7,000 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 is convertible at any time at the option of the holder into one share of Series A Common Stock and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

F1 · kind: Represents 7,000 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 one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

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 one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

F5 · balance_after: Consists of (i) 32,666 shares of Series B Common Stock and (ii) 23,334 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: 0001470831-25-000143 · wk-form4_1755651158.xml · nonDerivative · entry 2

Fernandez Gomez Luciano · CIK 0001730978 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 26,788

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.

F4 · balance_after: Consists of (i) 20,968 shares of Series A Common Stock and (ii) 5,820 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: 0001470831-25-000143 · wk-form4_1755651158.xml · nonDerivative · entry 1

Fernandez Gomez Luciano · CIK 0001730978 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 33,788

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 7,000 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 one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

SEC source: 0001470831-25-000140 · wk-form4_1755650858.xml · derivative · entry 5

Rowland Stephen Eric · CIK 0001639368 · President

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 438,953

Underlying: Series A Common Stock · 22,855 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 one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

F1 · kind: Represents 22,855 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 one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

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 one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

SEC source: 0001470831-25-000140 · wk-form4_1755650858.xml · nonDerivative · entry 2

Rowland Stephen Eric · CIK 0001639368 · President

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 424,374

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: 0001470831-25-000140 · wk-form4_1755650858.xml · nonDerivative · entry 1

Rowland Stephen Eric · CIK 0001639368 · President

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 458,700

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 22,855 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 one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

SEC source: 0001470831-25-000142 · wk-form4_1755651065.xml · derivative · entry 4

Whalen Amanda · CIK 0001991131 · Chief Financial Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 419,680

Underlying: Series A Common Stock · 29,513 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 one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

F1 · kind: Represents 29,513 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 one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

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 one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

F7 · balance_after: Consists of (i) 235,305 shares of Series B Common Stock and (ii) 184,375 unvested RSUs awarded under the Issuer's 2015 Stock Incentive Plan, each representing the contingent right to receive one share of Series B Common Stock upon vesting and settlement.

SEC source: 0001470831-25-000142 · wk-form4_1755651065.xml · nonDerivative · entry 3

Whalen Amanda · CIK 0001991131 · Chief Financial Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 485,515

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 $30.92 to $31.53 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

F6 · balance_after: Consists of (i) 46,483 shares of Series A Common Stock and (ii) 439,032 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: 0001470831-25-000142 · wk-form4_1755651065.xml · nonDerivative · entry 2

Whalen Amanda · CIK 0001991131 · Chief Financial Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 500,515

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

SEC source: 0001470831-25-000142 · wk-form4_1755651065.xml · nonDerivative · entry 1

Whalen Amanda · CIK 0001991131 · Chief Financial Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 547,344

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 29,513 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 one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

SEC source: 0000950170-25-109399 · 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: 23,827,778

Underlying: Series A Common Stock, par value $0.001 per share · 7,000,000 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) 14,082,751 shares of Series B Common Stock held by Fund IX-A, (ii) 8,793,072 shares of Series B Common Stock held by Fund IX-B, (iii) 868,334 shares of Series B Common Stock held by Kiwi Co-Invest Fund, (iv) 74,015 shares of Series B Common Stock held by Fund IX/VC IV, and (v) 9,606 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 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: 0000950170-25-109399 · 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: 500,000

F5 · balance_after: Consists of (i) 307,809 shares of Series A Common Stock held by Fund IX-A and (ii) 192,191 shares of Series A Common Stock held by Fund IX-B, in each case to facilitate charitable giving.

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 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: 0000950170-25-109399 · 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: 7,000,000

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 2) Summit Master Company, LLC, as the managing member of Summit Investors Management, LLC, has delegated voting and investment decisions with respect to the securities held by Fund IX/VC IV and Fund IX/VC IV (UK) to Summit Partners, L.P.

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: 0000950170-25-099676 · 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: 15,939,963

Underlying: Series A Common Stock · 344,383 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: 0000950170-25-099676 · 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: 2,755,057

Underlying: Series B Common Stock · 344,383 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: 0001470831-25-000093 · wk-form4_1752703165.xml · nonDerivative · entry 1

Rowland Stephen Eric · CIK 0001639368 · President

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 435,845

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 22, 2024.

F2 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $31.22 to $31.96 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.

F3 · balance_after: Consists of (i) 100,542 shares of the Issuer's Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), and (ii) 335,303 unvested restricted stock units awarded under the Issuer's 2023 Stock Option and Incentive Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement.

SEC source: 0001470831-25-000082 · wk-form4_1752523733.xml · derivative · entry 4

Whalen Amanda · CIK 0001991131 · Chief Financial Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 449,193

Underlying: Series A Common Stock · 15,000 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 one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

F1 · 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.

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 one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

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 one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

F5 · balance_after: Consists of (i) 189,818 shares of Series B Common Stock and (ii) 259,375 unvested RSUs awarded under the Issuer's 2015 Stock Incentive Plan, each representing the contingent right to receive one share of Series B Common Stock upon vesting and settlement.

SEC source: 0001470831-25-000082 · wk-form4_1752523733.xml · nonDerivative · entry 3

Whalen Amanda · CIK 0001991131 · Chief Financial Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 517,831

F1 · 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.

F4 · balance_after: Consists of (i) 34,799 shares of Series A Common Stock and (ii) 483,032 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: 0001470831-25-000082 · wk-form4_1752523733.xml · nonDerivative · entry 2

Whalen Amanda · CIK 0001991131 · Chief Financial Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 518,031

F1 · 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.

F3 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $31.33 to $32.32 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

SEC source: 0001470831-25-000082 · wk-form4_1752523733.xml · nonDerivative · entry 1

Whalen Amanda · CIK 0001991131 · Chief Financial Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 532,831

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 August 16, 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 one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

SEC source: 0001835830-25-000072 · wk-form4_1750192396.xml · nonDerivative · entry 2

Rowland Stephen Eric · CIK 0001639368 · President

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 442,924

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 22, 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 $33.81 to $33.85 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) 107,621 shares of the Issuer's Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), and (ii) 335,303 unvested restricted stock units awarded under the Issuer's 2023 Stock Option and Incentive Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement.

SEC source: 0001835830-25-000072 · wk-form4_1750192396.xml · nonDerivative · entry 1

Rowland Stephen Eric · CIK 0001639368 · President

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 443,224

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 22, 2024.

F2 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $33.93 to $34.92 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: 0001835830-25-000070 · wk-form4_1749855331.xml · derivative · entry 3

Whalen Amanda · CIK 0001991131 · Chief Financial Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 464,193

Underlying: Series A Common Stock · 11,204 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 one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

F1 · 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.

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 one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

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 one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

F5 · balance_after: Consists of (i) 204,818 shares of the Issuer's Series B Common Stock and (ii) 259,375 unvested RSUs awarded under the Issuer's 2015 Stock Incentive Plan, each representing the contingent right to receive one share of Series B Common Stock upon vesting and settlement.

SEC source: 0001835830-25-000070 · wk-form4_1749855331.xml · nonDerivative · entry 2

Whalen Amanda · CIK 0001991131 · Chief Financial Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 517,831

F1 · 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.

F3 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $33.14 to $33.92 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) 34,799 shares of Series A Common Stock and (ii) 483,032 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: 0001835830-25-000070 · wk-form4_1749855331.xml · nonDerivative · entry 1

Whalen Amanda · CIK 0001991131 · Chief Financial Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 532,831

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 August 16, 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 one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

SEC source: 0001835830-25-000069 · wk-form4_1749673657.xml · derivative · entry 3

Bialecki Andrew · CIK 0001991099 · Director · Chief Executive Officer · 10% owner

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 74,773,276

Underlying: Series A Common Stock · 100,000 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: Each share of the Issuer's Series B Common Stock, par value $0.001 per share ("Series B Common Stock"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

F1 · 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 one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

F1 · 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 one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

SEC source: 0001835830-25-000069 · wk-form4_1749673657.xml · nonDerivative · entry 2

Bialecki Andrew · CIK 0001991099 · Director · Chief Executive Officer · 10% owner

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 0

F3 · kind: Represents a bona fide gift of 100,000 shares of stock from the Reporting Person to a donor-advised fund. The Reporting Person directed the transfer of 100,000 shares of their Series B Common Stock, resulting in the automatic conversion of the shares into Series A Common Stock upon execution of the transfer.

SEC source: 0001835830-25-000069 · wk-form4_1749673657.xml · nonDerivative · entry 1

Bialecki Andrew · CIK 0001991099 · Director · Chief Executive Officer · 10% owner

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 100,000

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: Each share of the Issuer's Series B Common Stock, par value $0.001 per share ("Series B Common Stock"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

F2 · price: The Reporting Person directed the transfer of 100,000 shares of their Series B Common Stock in connection with a bona fide gift to a donor-advised fund, resulting in the automatic conversion of the shares into Series A Common Stock upon execution of the transfer pursuant to the Issuer's certificate of incorporation.

SEC source: 0001835830-25-000068 · wk-form4_1749673528.xml · nonDerivative · entry 2

Fernandez Gomez Luciano · CIK 0001730978 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 26,788

F2 · shares: Represents 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. The RSUs vest in full upon the earlier of (i) June 10, 2026 or (ii) the date of the Issuer's next annual meeting of stockholders, in each case subject to the Reporting Person's continued service as a member of the Issuer's board of directors through such vesting date.

F3 · balance_after: Consists of (i) 20,968 shares of Series A Common Stock and (ii) 5,820 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: 0001835830-25-000068 · wk-form4_1749673528.xml · nonDerivative · entry 1

Fernandez Gomez Luciano · CIK 0001730978 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 20,968

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").

SEC source: 0001835830-25-000067 · wk-form4_1749673357.xml · nonDerivative · entry 1

Weisman Tony · CIK 0001716921 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 89,352

F1 · shares: Represents restricted stock units ("RSUs") awarded under the Issuer's 2023 Stock Option and Incentive Plan, each representing the contingent right to receive one share of the Issuer's Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), upon vesting and settlement. The RSUs vest in full upon the earlier of (i) June 10, 2026 or (ii) the date of the Issuer's next annual meeting of stockholders, in each case subject to the Reporting Person's continued service as a member of the Issuer's board of directors through such vesting date.

F2 · balance_after: Consists of (i) 83,532 shares of Series A Common Stock and (ii) 5,820 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: 0001835830-25-000064 · wk-form4_1749673028.xml · nonDerivative · entry 1

St. Ledger Susan · CIK 0001673606 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 14,352

F1 · shares: Represents restricted stock units ("RSUs") awarded under the Issuer's 2023 Stock Option and Incentive Plan, each representing the contingent right to receive one share of the Issuer's Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), upon vesting and settlement. The RSUs vest in full upon the earlier of (i) June 10, 2026 or (ii) the date of the Issuer's next annual meeting of stockholders, in each case subject to the Reporting Person's continued service as a member of the Issuer's board of directors through such vesting date.

F2 · balance_after: Consists of (i) 8,532 shares of Series A Common Stock and (ii) 5,820 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: 0001835830-25-000065 · wk-form4_1749673180.xml · nonDerivative · entry 1

Ceran Jennifer · CIK 0001652155 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 14,352

F1 · shares: Represents restricted stock units ("RSUs") awarded under the Issuer's 2023 Stock Option and Incentive Plan, each representing the contingent right to receive one share of the Issuer's Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), upon vesting and settlement. The RSUs vest in full upon the earlier of (i) June 10, 2026 or (ii) the date of the Issuer's next annual meeting of stockholders, in each case subject to the Reporting Person's continued service as a member of the Issuer's board of directors through such vesting date.

F2 · balance_after: Consists of (i) 8,532 shares of Series A Common Stock and (ii) 5,820 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: 0001835830-25-000066 · wk-form4_1749673269.xml · nonDerivative · entry 1

Oulman Roxanne · CIK 0001523073 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 14,352

F1 · shares: Represents restricted stock units ("RSUs") awarded under the Issuer's 2023 Stock Option and Incentive Plan, each representing the contingent right to receive one share of the Issuer's Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), upon vesting and settlement. The RSUs vest in full upon the earlier of (i) June 10, 2026 or (ii) the date of the Issuer's next annual meeting of stockholders, in each case subject to the Reporting Person's continued service as a member of the Issuer's board of directors through such vesting date.

F2 · balance_after: Consists of (i) 8,532 shares of Series A Common Stock and (ii) 5,820 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: 0000950170-25-082604 · 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: 30,827,778

Underlying: Series A Common Stock, par value $0.001 per share · 4,000,000 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.

F5 · balance_after: Consists of (i) 18,219,907 shares of Series B Common Stock held by Fund IX-A, (ii) 11,376,255 shares of Series B Common Stock held by Fund IX-B, (iii) 1,123,429 shares of Series B Common Stock held by Kiwi Co-Invest Fund, (iv) 95,759 shares of Series B Common Stock held by Fund IX/VC IV, and (v) 12,428 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 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: 0000950170-25-082604 · 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: 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 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: 0000950170-25-082604 · 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: 4,000,000

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 2) Summit Master Company, LLC, as the managing member of Summit Investors Management, LLC, has delegated voting and investment decisions with respect to the securities held by Fund IX/VC IV and Fund IX/VC IV (UK) to Summit Partners, L.P.

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: 0000950170-25-075445 · 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: 34,827,778

Underlying: Series A Common Stock, par value $0.001 per share · 4,000,000 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.

F5 · balance_after: Consists of (i) 20,583,996 shares of Series B Common Stock held by Fund IX-A, (ii) 12,852,359 shares of Series B Common Stock held by Fund IX-B, (iii) 1,269,198 shares of Series B Common Stock held by Kiwi Co-Invest Fund, (iv) 108,184 shares of Series B Common Stock held by Fund IX/VC IV, and (v) 14,041 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 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: 0000950170-25-075445 · 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: 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 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: 0000950170-25-075445 · 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: 4,000,000

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 2) Summit Master Company, LLC, as the managing member of Summit Investors Management, LLC, has delegated voting and investment decisions with respect to the securities held by Fund IX/VC IV and Fund IX/VC IV (UK) to Summit Partners, L.P.

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: 0001835830-25-000060 · wk-form4_1747443579.xml · nonDerivative · entry 2

Bialecki Andrew · CIK 0001991099 · Director · Chief Executive Officer · 10% owner

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 0

F1 · kind: Represents shares of the Issuer's Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), sold in an underwritten registered offering, the proceeds of which were used to satisfy taxes incurred in connection with stock option exercises.

SEC source: 0001835830-25-000058 · wk-form4_1747442865.xml · nonDerivative · entry 4

Edmond Landon · CIK 0001991399 · Chief Legal Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 404,744

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 $34.50 to $35.37 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

F6 · balance_after: Consists of (i) 99,831 shares of Series A Common Stock and (ii) 304,913 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: 0001835830-25-000056 · wk-form4_1747442629.xml · nonDerivative · entry 2

Galvin Carmel · CIK 0001733091 · Chief People Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 711,805

F2 · kind: These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on November 26, 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 $34.54 to $35.38 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

F4 · balance_after: Consists of (i) 71,504 shares of Series A Common Stock and (ii) 640,301 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: 0001835830-25-000057 · wk-form4_1747442766.xml · nonDerivative · entry 6

Rowland Stephen Eric · CIK 0001639368 · President

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 450,003

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 22, 2024

F7 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $34.50 to $35.37 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

F8 · balance_after: Consists of (i) 114,700 shares of Series A Common Stock and (ii) 335,303 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: 0001835830-25-000055 · wk-form4_1747442485.xml · nonDerivative · entry 3

Whalen Amanda · CIK 0001991131 · Chief Financial Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 521,627

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 $34.50 to $35.37 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

F6 · balance_after: Consists of (i) 38,595 shares of Series A Common Stock and (ii) 483,032 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: 0001835830-25-000058 · wk-form4_1747442865.xml · derivative · entry 6

Edmond Landon · CIK 0001991399 · Chief Legal Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 67,500

Underlying: Series A Common Stock · 11,074 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 one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

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 one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

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 one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

F7 · balance_after: Consists of 67,500 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: 0001835830-25-000058 · wk-form4_1747442865.xml · derivative · entry 5

Edmond Landon · CIK 0001991399 · Chief Legal Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 78,574

Underlying: Series A Common Stock · 11,426 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 one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

F1 · kind: Represents 11,426 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 one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

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 one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

SEC source: 0001835830-25-000058 · wk-form4_1747442865.xml · nonDerivative · entry 3

Edmond Landon · CIK 0001991399 · Chief Legal Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 414,709

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 · 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 one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

SEC source: 0001835830-25-000058 · wk-form4_1747442865.xml · nonDerivative · entry 2

Edmond Landon · CIK 0001991399 · Chief Legal Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 403,635

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.