1stdibs.com, Inc.

Rule 10b5-1 Trading Arrangements

During the quarter ended December 31, 2025, the following officers (as defined in Rule 16a-1(f) of the Exchange Act) adopted a Rule 10b5-1 trading arrangement, as defined in Item 408 of Regulation S-K, for the sale of our common stock. Shares in each 10b5-1 trading arrangement that are subject to restricted stock units and stock options may only be traded following satisfaction of applicable vesting requirements. In addition, because of pricing (such as future share price targets) and timing conditions in each 10b5-1 trading arrangement, it is not yet determinable how many shares actually will be sold under each plan prior to its expiration date.

On December 9, 2025, Melanie Goins, our General Counsel and Chief People Officer, entered into a 10b5-1 trading plan during an open insider trading window, intended to satisfy the affirmative defense of Rule 10b5-1(c) under the Exchange Act and the Company’s policies regarding insider transactions for trades over a period of time from March 9, 2026 until December 1, 2026 or such earlier time as when 45,000 shares of the Company’s common stock are sold.

During the quarter ended December 31, 2025, no other directors or officers adopted, modified, orterminated a “Rule 10b5-1 trading arrangement” or a “non-Rule 10b5-1 trading arrangement,” as defined in Item 408 of Regulation S-K.