144 0001629398 XXXXXXXX LIVE 0001600641 1stdibs.com, Inc. 001-40453 300 PARK AVENUE SOUTH 10TH FLOOR NEW YORK NY 10010 212-627-3929 Insight Venture Partners IX, L.P. 10% Stockholder COMMON RAYMOND JAMES & ASSOCIATES

880 CARILLON PKWY ST. PETERSBURG FL 33716

89352 536112.00 39745811 03/28/2024 NASDAQ COMMON 06/16/2015 Purchase - reflects 1:3 stock split Michael J. Bruno II N 3120840 06/16/2015 WIRED TO SELLER N Insight Venture Partners IX (Co-Investors), L.P.

1114 Avenue of the Americas, 36th Floor NEW YORK NY 10036

COMMON 03/14/2024 370 2271.02 Insight Venture Partners (Delaware) IX, L.P.

1114 Avenue of the Americas, 36th Floor NEW YORK NY 10036

COMMON 03/14/2024 1963 12048.70 Insight Venture Partners (Cayman) IX, L.P.

1114 Avenue of the Americas, 36th Floor NEW YORK NY 10036

COMMON 03/14/2024 9204 56493.23 Insight Venture Partners IX, L.P.

1114 AVENUE OF THE AMERICAS, 36TH FLOOR NEW YORK NY 10036

COMMON 03/14/2024 18522 113686.18 Insight Venture Partners IX (Co-Investors), L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/15/2024 178 1078.97 Insight Venture Partners (Delaware) IX, L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/15/2024 943 5715.81 Insight Venture Partners (Cayman) IX, L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/15/2024 4422 26803.07 Insight Venture Partners IX, L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/15/2024 8898 53933.45 Insight Venture Partners IX (Co-Investors), L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/18/2024 218 1312.60 Insight Venture Partners (Delaware) IX, L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/18/2024 1156 6960.39 Insight Venture Partners (Cayman) IX, L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/18/2024 5423 32652.43 Insight Venture Partners IX, L.P.

1114 AVENUES OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/18/2024 10913 65708.26 Insight Venture Partners IX (Co-Investors), L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/19/2024 108 649.39 Insight Venture Partners (Delaware) IX, L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/19/2024 572 3439.38 Insight Venture Partners (Cayman) IX, L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/19/2024 2680 16114.57 Insight Venture Partners IX, L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/19/2024 5394 32433.58 Insight Venture Partners IX (Co-Investors), L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/20/2024 714 4301.14 Insight Venture Partners (Delaware) IX, L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/20/2024 3789 22824.94 Insight Venture Partners (Cayman) IX, L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/20/2024 17769 107040.46 Insight Venture Partners IX, L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/20/2024 35760 215418.24 Insight Venture Partners IX (Co-Investors), L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/21/2024 396 2391.09 Insight Venture Partners (Delaware) IX, L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/21/2024 2102 12692.09 Insight Venture Partners (Cayman) IX, L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/21/2024 9858 59523.59 Insight Venture Partners IX, L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/21/2024 19841 119801.94 Insight Venture Partners IX (Co-Investors), L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/22/2024 293 1813.99 Insight Venture Partners (Delaware) IX, L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/22/2024 1557 9639.54 Insight Venture Partners (Cayman) IX, L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/22/2024 7302 45207.41 Insight Venture Partners IX, L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/22/2024 14695 90978.21 Insight Venture Partners IX (Co-Investors), L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/25/2024 396 2400.35 Insight Venture Partners (Delaware) IX, L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/25/2024 2102 12741.27 Insight Venture Partners (Cayman) IX, L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/25/2024 9857 59748.21 Insight Venture Partners IX, L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/25/2024 19838 120248.04 Insight Venture Partners IX (Co-Investors), L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/26/2024 611 3731.32 Insight Venture Partners (Delaware) IX, L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/26/2024 3245 19816.89 Insight Venture Partners (Cayman) IX, L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/26/2024 15218 92934.80 Insight Venture Partners IX, L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/26/2024 30624 187036.03 Insight Venture Partners IX (Co-Investors), L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/27/2024 412 2486.17 Insight Venture Partners (Delaware) IX, L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/27/2024 2189 13209.30 Insight Venture Partners (Cayman) IX, L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/27/2024 10264 61937.08 Insight Venture Partners IX, L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/27/2024 20657 124652.60 Insight Venture Partners IX (Co-Investors), L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/28/2024 1163 7001.26 Insight Venture Partners (Delaware) IX, L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/28/2024 6171 37149.42 Insight Venture Partners (Cayman) IX, L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/28/2024 28947 174260.67 Insight Venture Partners IX, L.P.

1114 AVENUE OF THE AMERICAS, 36TH FL NEW YORK NY 10036

COMMON 03/28/2024 58263 350743.26 03/28/2024 MOHAMMED ALSHATRI, as duly authorized representative of Raymond James & Associates, Inc., as attorney-in-fact for Insight Venture Partners IX, L.P.