X0508 4 2026-02-13 0 0001835830 Klaviyo, Inc. KVYO 0001991131 Whalen Amanda C/O KLAVIYO, INC. 125 SUMMER STREET, 6TH FLOOR BOSTON MA 02110 0 1 0 0 Chief Financial Officer 1 Series A Common Stock 2026-02-13 4 C 0 14000 A 456219 D Series A Common Stock 2026-02-13 4 S 0 9281 19.01 D 446938 D Series A Common Stock 2026-02-13 4 S 0 4719 18.63 D 442219 D Series A Common Stock 2026-02-15 4 C 0 29513 A 471732 D Series A Common Stock 2026-02-15 4 F 0 45307 18.60 D 426425 D Series B Common Stock 2026-02-13 4 C 0 14000 0 D Series A Common Stock 14000 330918 D Series B Common Stock 2026-02-15 4 C 0 29513 0 D Series A Common Stock 29513 301405 D These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on August 21, 2025. 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. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $18.76 to $19.75 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $18.52 to $18.75 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote. Represents 29,513 shares of Series B Common Stock automatically converted into shares of Series A Common Stock in connection with tax withholding obligations related to the vesting and settlement of restricted stock units ("RSUs"). 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. Consists of (i) 66,394 shares of Series A Common Stock and (ii) 360,031 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. Consists of (i) 267,030 shares of Series B Common Stock and (ii) 34,375 unvested RSUs awarded under the Issuer's 2015 Stock Incentive Plan, each representing the contingent right to receive one share of Series B Common Stock upon vesting and settlement. /s/ Landon Edmond, Attorney-in-Fact 2026-02-18