Table of Contents As filed with the Securities and Exchange Commission on September 18, 2023. Registration No. 333-274211 UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 Amendment No 2. to FORM S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 Klaviyo, Inc. (Exact Name of Registrant as Specified in Its Charter) (State or Other Jurisdiction of Incorporation or Organization) (Primary Standard Industrial Classification Code Number) 125 Summer Street 6th Floor Boston, MA 02110 ...

(State or Other Jurisdiction of Incorporation or Organization) UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 Amendment No 1. to FORM S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 Klaviyo, Inc. (Exact Name of Registrant as Specified in Its Charter) Table of Contents As filed with the Securities and Exchange Commission on September 11, 2023. Registration No. 333-274211 Delaware 7372 46-0989964 (Primary Standard Industrial Classification Code Number) 125 Summer Street 6t ...

Table of Contents As filed with the Securities and Exchange Commission on August 25, 2023. Registration No. 333- UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 Klaviyo, Inc. (Exact Name of Registrant as Specified in Its Charter) (Primary Standard Industrial Classification Code Number) 125 Summer Street 6th Floor Boston, MA 02110 (617) 213-1788 (Address, Including Zip Code, and Telephone Number, Including Area Code, of ...