X0306 4 2021-09-17 0 0001861795 Definitive Healthcare Corp. DH 0001824265 SEA VII Management, LLC 140 NEW MONTGOMERY STREET, 20TH FLOOR SAN FRANCISCO CA 94105 1 0 1 0 0001879386 SE VII DHC AIV, L.P. 140 NEW MONTGOMERY STREET, 20TH FLOOR SAN FRANCISCO 94105 1 0 1 0 0001626997 Spectrum VII Investment Managers' Fund, L.P. 140 NEW MONTGOMERY STREET, 20TH FLOOR SAN FRANCISCO 94105 1 0 1 0 0001879377 SE VII DHC AIV Feeder, L.P. 140 NEW MONTGOMERY STREET, 20TH FLOOR SAN FRANCISCO CA 94105 1 0 1 0 0001822087 Spectrum VII Co-Investment Fund, L.P. 140 NEW MONTGOMERY STREET, 20TH FLOOR SAN FRANCISCO CA 94105 1 0 1 0 0001824228 Spectrum Equity Associates VII, L.P. 140 NEW MONTGOMERY STREET, 20TH FLOOR SAN FRANCISCO CA 94105 1 0 1 0 Class A Common Stock 2021-09-17 4 S 0 66857 25.3125 D 2885876 I See notes Class B Common Stock 2021-09-17 4 C 0 641983 D 27710989 I See notes LLC Units of AIDH Topco, LLC 2021-09-17 4 C 0 641983 25.3125 D Class A Common Stock 641983 27710989 I See notes See Exhibit 99.1 for text of footnote (1). See Exhibit 99.1 for text of footnote (2). See Exhibit 99.1 for text of footnote (3). See Exhibit 99.1 for text of footnote (4). See Exhibit 99.1 for text of footnote (5). See Exhibit 99.1 for text of footnote (6). Christopher T. Mitchell, a Managing Director of Spectrum and Jeffrey C. Haywood, a Managing Director of Spectrum (together, the "Spectrum Directors"), each serve on the board of directors of the Issuer, and have been deputized to represent the Reporting Persons on the board of directors. By virtue of the Spectrum Directors' representation, for purposes of Section 16 of the Securities Exchange Act of 1934, each of the Reporting Persons may be deemed directors by deputization of the Issuer. The Spectrum Directors have filed separate Section 16 reports disclosing securities of the Issuer that they may be deemed to beneficially own for Section 16 purposes. Exhibit 99.1 (Footnotes to Form 4). SEA VII MANAGEMENT, LLC, By: /s/ Carolina A. Picazo, Chief Administrative Officer & Chief Compliance Officer 2021-09-21 SE VII DHC AIV, L.P., By: Spectrum Equity Associates VII, L.P., its general partner, By: SEA VII Management, LLC, its general partner, By: /s/Carolina A. Picazo, its Chief Administrative Officer & Chief Compliance Officer 2021-09-21 SE VII DHC AIV FEEDER, L.P., By: Spectrum Equity Associates VII, L.P., its general partner, By: SEA Management, LLC, its general partner, By: /s/ Carolina A. Picazo, Chief Administrative Officer & Chief Compliance Officer 2021-09-21 SPECTRUM VII INVESTMENT MANAGERS' FUND, L.P., By: SEA Management, LLC, its general partner, By: /s/ Carolina A. Picazo, Chief Administrative Officer & Chief Compliance Officer 2021-09-21 SPECTRUM VII CO-INVESTMENT FUND, L.P., By: /s/ Carolina A. Picazo, Chief Administrative Officer & Chief Compliance Officer 2021-09-21 SPECTRUM EQUITY ASSOCIATES VII, L.P., By: SEA Management, LLC, its general partner, By: /s/ Carolina A. Picazo, Chief Administrative Officer & Chief Compliance Officer 2021-09-21