X0306 4 2021-08-16 0 0001600641 1stdibs.com, Inc. DIBS 0001237860 ROSENBLATT DAVID S 51 ASTOR PLACE, THIRD FLOOR NEW YORK NY 10003 1 1 0 0 Chief Executive Officer Common Stock 2021-08-17 4 P 0 43073 14.9292 A 1464548 D Common Stock 2021-08-18 4 P 0 6927 15.835 A 1471475 D Common Stock 2021-08-16 4 P 0 44197 14.89 A 659499 I By 2012 David Rosenblatt Family Trust dtd 11/30/2012 Common Stock 2021-08-17 4 P 0 5803 14.38 A 665302 I By 2012 David Rosenblatt Family Trust dtd 11/30/2012 The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $14.26 to $14.46, inclusive. The reporting person undertakes to provide to Issuer, any security holder of 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. /s/ Melanie Goins, Attorney-In-Fact for David S. Rosenblatt 2021-08-18