1stDibs Investor Presentation Deck

Reconciliation of Quarterly Net Income to Adj. EBITDA Q1 2023 Q4 2022 (Amounts in thousands) Net loss Excluding: 13 Depreciation and amortization Stock-based compensation expense Other income, net Provision for income taxes Strategic alternative expenses Adjusted EBITDA (non-GAAP) Divided by: Net revenue Adjusted EBITDA Margin (non-GAAP) S S $ Q3 2023 (3,305) S 449 2,982 (1,928) (1,802) S 20,663 $ -8.7% Q2 2023 (8,320) S 427 3,252 (2,117) 2,179 (4,579) S 20,921 $ -21.9% 1€DIBS (8,133) S (6,861) S 939 3,106 (2,048) 882 (5,254) S 22,178 $ -23.7% 521 3,552 (1,804) 37 80 (4,475) S 22,957 $ -19.5% Q3 2022 (9,028) 708 3,154 (870) 580 (5,456) 22,729 -24.0%

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