Definitive Healthcare (DH) S-1 15 Nov 21 IPO registration Financial data

Cover Page

Cover Page	9 Months Ended
	Sep. 30, 2021
Cover [Abstract]
Document Type	S-1
Amendment Flag	false
Entity Filer Category	Non-accelerated Filer
Entity Registrant Name	Definitive Healthcare Corp.
Entity Central Index Key	0001861795
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	false

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($)	Sep. 30, 2021	May 24, 2021	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 189,752,000	$ 100	$ 24,774,000	$ 8,618,000
Accounts receivable, net	27,886,000		33,108,000	25,021,000
Prepaid expenses and other current assets	3,642,000		3,016,000	1,699,000
Current portion of deferred contract costs	5,359,000		2,947,000	769,000
Total current assets	226,639,000	100	63,845,000	36,107,000
Property and equipment, net	4,697,000		3,248,000	2,558,000
Other assets	747,000		472,000	607,000
Deferred contract costs, net of current portion	9,388,000		5,952,000	2,116,000
Deferred tax asset	161,000		161,000	212,000
Intangible assets, net	366,723,000		410,237,000	446,381,000
Goodwill	1,261,444,000		1,261,444,000	1,233,173,000
Total assets	1,869,799,000		1,745,359,000	1,721,154,000
Current liabilities:
Accounts payable	7,055,000		5,662,000	2,157,000
Accrued expenses and other current liabilities	19,296,000		17,321,000	10,348,000
Members' distribution payable				6,935,000
Current portion of deferred revenue	69,811,000		61,060,000	45,977,000
Current portion of term loan	6,875,000		4,680,000	4,500,000
Total current liabilities	103,037,000		88,723,000	69,917,000
Long term liabilities:
Deferred revenue	368,000		140,000	148,000
Tax receivable agreements liability	146,106,000		0
Term loan, net of current portion	265,388,000		457,197,000	434,849,000
Deferred tax liabilities	71,341,000		0
Other long-term liabilities	475,000		3,736,000
Total liabilities	586,715,000		549,796,000	504,914,000
Stockholder's equity
Common stock, par value		0.01
Additional paid in capital	700,773,000	99.99	0
Accumulated other comprehensive loss	24,000		(131,000)
Accumulated deficit	(7,798,000)		(109,855,000)	(55,758,000)
Noncontrolling interests	590,177,000		0
Total stockholder's equity	1,283,084,000	$ 100,000	1,195,563,000	1,216,240,000
Total liabilities and equity	1,869,799,000		1,745,359,000	1,721,154,000
Member Units [Member]
Stockholder's equity
Total stockholder's equity			1,195,694,000	1,216,240,000
Common Class A [Member]
Stockholder's equity
Common stock, par value	88,000		1,303,058,000	1,271,254,000
Total stockholder's equity	88,000
Common Class B [Member]
Stockholder's equity
Common stock, par value	$ 0		$ 2,491,000	$ 744,000

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical)	Sep. 30, 2021$ / sharesshares
Definitive Healthcare Corp [Member] | Common Class A [Member]
Common stock par or stated value per share | $ / shares	$ 0.001
Common stock shares authorized	600,000,000
Common stock shares issued	88,263,333
Common stock shares outstanding	88,263,333
Definitive Healthcare Corp [Member] | Common Class B [Member]
Common stock par or stated value per share | $ / shares	$ 0
Common stock shares authorized	65,000,000
Common stock shares issued	60,020,525
Common stock shares outstanding	57,220,661

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	6 Months Ended		9 Months Ended			12 Months Ended
	Dec. 31, 2019	Jul. 15, 2019	Sep. 30, 2021		Sep. 30, 2020	Dec. 31, 2020
Revenue	$ 40,045	$ 45,458	$ 119,841		$ 84,659	$ 118,317
Cost of revenue:
Cost of revenue exclusive of amortization shown below	4,668	4,830	13,895		7,876	11,085
Amortization	8,614	498	15,896		14,278	19,383
Gross Profit	26,763	40,130	90,050		62,505	87,849
Operating expenses:
Sales and marketing	10,814	16,039	39,003		23,542	34,332
Product development	3,484	3,961	12,817		7,566	11,062
General and administrative	6,365	3,979	18,891		8,105	12,927
Depreciation and amortization	22,459	1,967	28,814		30,037	40,197
Transaction expenses	14,703	1,151	3,332		748	3,776
Total operating expenses	57,825	27,097	102,857		69,998	102,294
Loss from operations	(31,062)	13,033	(12,807)		(7,493)	(14,445)
Other expense, net:
Foreign currency transaction gain			143			(222)
Interest expense, net	(18,204)	(165)	(23,956)		(27,802)	(36,490)
Loss from extinguishment of debt			(9,873)
Total other expense, net	(18,204)	(165)	(33,686)		(27,802)	(36,712)
Net Loss			(46,493)		(35,295)
Less: net loss attributable to Definitive OpCo prior to the Reorganization transactions			(33,343)		(35,295)
Less: Net loss attributable to noncontrolling interests			(5,172)
Net loss attributable to Definitive Healthcare Corp	$ (49,266)	$ 12,868	$ (7,978)		$ (35,295)	$ (51,157)
Net loss per share of Class A Common Stock:
Basic and diluted	$ (0.39)					$ (0.40)
Weighted average Common Stock outstanding:
Basic and diluted	126,794,329		88,263,333	[1]		127,682,376
Common Class A [Member]
Other expense, net:
Less: Net loss attributable to noncontrolling interests			$ (5,172)
Net loss per share of Class A Common Stock:
Basic and diluted			$ (0.09)
Weighted average Common Stock outstanding:
Basic and diluted			88,263,333,000
[1]	Basic and diluted net loss per share of Class A Common Stock is applicable only for the period from September 15, 2021 through September 30, 2021, which is the period following the initial public offering (“IPO”) and related Reorganization Transactions (as defined in Note 1 to the Unaudited Consolidated Financial Statements). See Note 16 for the number of shares used in the computation of net loss per share of Class A Common Stock and the basis for the computation of net loss per share.

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2019	Jul. 15, 2019	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Statement of Comprehensive Income [Abstract]
Net loss	$ (49,266)	$ 12,868	$ (46,493)	$ (35,295)	$ (51,157)
Other comprehensive loss:
Foreign currency translation adjustments			155		(131)
Comprehensive loss			(46,338)	(35,295)
Less: Net loss attributable to Definitive OpCo prior to the Reorganization Transactions			(33,201)
Less: Comprehensive loss attributable to noncontrolling interests			(5,167)
Comprehensive loss attributable to Definitive Healthcare Corp	$ (49,266)	$ 12,868	$ (7,970)	$ (35,295)	$ (51,288)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Changes in Members' Equity and Total Equity - USD ($) $ in Thousands	Total	Member Units [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Noncontrolling Interests [Member]	Common Class A [Member]	Common Class A [Member]Member Units [Member]	Common Class B [Member]	Common Class B [Member]Member Units [Member]	Legacy Class A [Member]	Legacy Class A [Member]Member Units [Member]	Legacy Class B [Member]Member Units [Member]
Balance at Beginning at Dec. 31, 2018	$ 73,827		$ (42,598)	$ 38,925								$ 77,500
Balance at Beginning, shares at Dec. 31, 2018												7,750,000	88,716
Adoption of ASC 606 (See Note 2)	5,415		5,415
Distribution to members	(468)		(468)
Vesting of Class B Units and unit-based compensation, Shares													180,137
Recapitalization (See Note 12)	(97,449)		31,844	(51,793)								$ (77,500)
Recapitalization (See Note 12), Shares												(7,750,000)	(268,853)
Capital contribution (See Note 3 and 12)	1,267,257							$ 1,267,257
Capital contribution (See Note 3 and 12), Shares								126,725,743
Impacts of Reorganization Transactions and Intial Public Offering IPO
Net loss subsequent to Reorganization Transactions	12,868			12,868
Equity-based compensation subsequent to Reorganization Transactions	5,807		5,807
Balance at Ending at Jul. 15, 2019	1,267,257	$ 97,449	(31,844)	51,793				$ 1,267,257				$ 77,500
Balance at Ending, shares at Jul. 15, 2019								126,725,743				7,750,000	268,853
Distribution to members	(6,492)			(6,492)
Capital contribution (See Note 3 and 12)	3,997							$ 3,997
Capital contribution (See Note 3 and 12), Shares								399,692
Impacts of Reorganization Transactions and Intial Public Offering IPO
Net loss subsequent to Reorganization Transactions	(49,266)			(49,266)
Equity-based compensation subsequent to Reorganization Transactions	744									$ 744
Balance at Ending at Dec. 31, 2019	1,216,240			(55,758)				$ 1,271,254
Balance at Ending, shares at Dec. 31, 2019								127,125,435		744
Balance at Ending at Dec. 31, 2019	1,216,240	1,216,240
Equity-based compensation		430
Impacts of Reorganization Transactions and Intial Public Offering IPO
Net loss subsequent to Reorganization Transactions		(13,835)
Balance at Ending at Mar. 31, 2020		1,202,835
Balance at Beginning at Dec. 31, 2019	1,216,240	1,216,240
Balance at Beginning at Dec. 31, 2019	1,216,240			(55,758)				$ 1,271,254
Balance at Beginning, shares at Dec. 31, 2019								127,125,435		744
Impacts of Reorganization Transactions and Intial Public Offering IPO
Net loss subsequent to Reorganization Transactions	(35,295)
Balance at Ending at Sep. 30, 2020		1,180,168
Balance at Beginning at Dec. 31, 2019	1,216,240	1,216,240
Balance at Beginning at Dec. 31, 2019	1,216,240			(55,758)				$ 1,271,254
Balance at Beginning, shares at Dec. 31, 2019								127,125,435		744
Distribution to members	(2,940)			(2,940)
Vesting of Class B Units	1,747									$ 1,747
Vesting of Class B Units and unit-based compensation, Shares										474,920
Capital contribution (See Note 3 and 12)	31,804							$ 31,804
Capital contribution (See Note 3 and 12), Shares								3,120,555
Comprehensive loss	(131)				$ (131)
Impacts of Reorganization Transactions and Intial Public Offering IPO
Net loss subsequent to Reorganization Transactions	(51,157)			(51,157)
Balance at Ending at Dec. 31, 2020	1,195,563			(109,855)	(131)			$ 1,303,058		$ 2,491
Balance at Ending, shares at Dec. 31, 2020								130,245,990		474,920
Balance at Ending at Dec. 31, 2020	1,195,563	1,195,694			(131)
Balance at Beginning at Mar. 31, 2020		1,202,835
Distribution to members		(48)
Equity-based compensation		442
Impacts of Reorganization Transactions and Intial Public Offering IPO
Net loss subsequent to Reorganization Transactions		(11,498)
Balance at Ending at Jun. 30, 2020		1,191,731
Distribution to members		(2,059)
Equity-based compensation		458
Impacts of Reorganization Transactions and Intial Public Offering IPO
Net loss subsequent to Reorganization Transactions		(9,962)
Balance at Ending at Sep. 30, 2020		1,180,168
Balance at Beginning at Dec. 31, 2020	1,195,563	1,195,694			(131)
Net loss prior to Reorganization Transactions	(10,487)	(10,487)
Other comprehensive income (loss) prior to Reorganization Transactions					163	$ 163
Equity-based compensation prior to Reorganization Transactions	406	406
Balance at Ending at Mar. 31, 2021	1,185,645	1,185,613			32
Balance at Beginning at Dec. 31, 2020	1,195,563	1,195,694			(131)
Balance at Beginning at Dec. 31, 2020	1,195,563			(109,855)	(131)			$ 1,303,058		$ 2,491
Balance at Beginning, shares at Dec. 31, 2020								130,245,990		474,920
Impacts of Reorganization Transactions and Intial Public Offering IPO
Net loss subsequent to Reorganization Transactions	(46,493)						$ (7,978)
Balance at Ending at Sep. 30, 2021	1,283,084		700,773	(7,978)	24	590,177	$ 88
Balance at Ending , Shares at Sep. 30, 2021							88,263,333		60,020,525
Balance at Beginning at Mar. 31, 2021	1,185,645	1,185,613			32
Net loss prior to Reorganization Transactions	(15,040)	(15,040)
Other comprehensive income (loss) prior to Reorganization Transactions	(19)				(19)
Equity-based compensation prior to Reorganization Transactions	1,615	1,615
Members' contributions prior to Reorganization Transactions	5,500	5,500
Distributions to members prior to Reorganization Transactions	(3,328)	(3,328)
Balance at Ending at Jun. 30, 2021	1,174,373	1,174,360			13
Net loss prior to Reorganization Transactions	(7,816)	(7,816)
Other comprehensive income (loss) prior to Reorganization Transactions	(2)				(2)
Equity-based compensation prior to Reorganization Transactions	(278)	(278)
Distributions to members prior to Reorganization Transactions	(3,811)	(3,811)
Impacts of Reorganization Transactions and Intial Public Offering IPO
Initial effect of the Reorganization Transactions and IPO on noncontrolling interests	(217,446)	$ (1,162,455)	351,075			593,861	$ 73
Initial effect of the Reorganization Transactions and IPO on noncontrolling interests , Shares							72,871,733		61,262,052
Issuance of Class A Common Stock in IPO, net of costs	441,418		441,400				$ 18
Issuance of Class A Common Stock in IPO, net of costs, Shares							17,888,888
Repurchase of Definitive Healthcare Corp. shares in connection with the IPO	(63,212)		(63,209)				$ (3)
Repurchase of Definitive Healthcare Corp. shares in connection with the IPO, Shares							(2,497,288)
Repurchase of Definitive OpCo units in connection with IPO	(29,600)		(29,600)
Repurchase of Definitive OpCo units in connection with IPO, Shares									(1,169,378)
Net loss subsequent to Reorganization Transactions				(7,978)		(5,172)					$ (13,150)
Other comprehensive income subsequent to Reorganization Transactions and IPO	13				13
Equity-based compensation subsequent to Reorganization Transactions	2,595		1,574			1,021
Forfeited incentive units, Shares									(72,149)
Vested incentive units, value			(467)			467
Balance at Ending at Sep. 30, 2021	$ 1,283,084		$ 700,773	$ (7,978)	$ 24	$ 590,177	$ 88
Balance at Ending , Shares at Sep. 30, 2021							88,263,333		60,020,525

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Changes in Members' Equity and Total Equity (Parenthetical) $ in Thousands	3 Months Ended
	Sep. 30, 2021USD ($)
Capital Unit, Class A [Member] | IPO [Member]
Stock Issuance Cost Net	$ 11,394

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2019	Jul. 15, 2019	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Cash flows provided by operating activities:
Net loss	$ (49,266)	$ 12,868	$ (46,493)	$ (35,295)	$ (51,157)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and Amortization	456	423	1,193	817	1,152
Amortization of intangible assets	30,617	2,042	43,517	43,498	58,429
Amortization of deferred contract costs	189	824	3,195	1,038	1,671
Equity-based compensation	744	5,807	4,338	1,330	1,747
Noncash paid in kind interest expense	3,041			7,371	7,371
Amortization of debt issuance costs	1,082		1,522	1,541	2,061
Provision for doubtful accounts receivable	333		76	579	895
Loss on extinguishment of debt			9,843
Changes in fair value of contingent consideration			3,169		2,636
Changes in operating assets and liabilities:
Accounts receivable	(12,494)	3,872	5,179	3,936	(8,294)
Prepaid expenses and other current assets	39	(203)	(561)	(39)	(709)
Deferred contract costs	(3,075)	(2,239)	(9,043)	(4,341)	(7,685)
Accounts payable, accrued expenses and other current liabilities	7,396	557	(3,965)	(7,283)	2,996
Deferred revenue	13,805	4,776	9,023	1,392	12,104
Net cash provided by operating activities	(7,133)	28,727	20,993	14,544	23,217
Cash flows used in investing activities:
Purchases of property, equipment, and other assets	(1,171)	(729)	(5,662)	(1,061)	(1,395)
Cash paid for acquisitions, net of cash acquired	(1,108,197)	(29,831)		(6,935)	(22,467)
Net cash used in investing activities	(1,109,368)	(30,560)	(5,662)	(7,996)	(23,862)
Cash flows provided by (used in) financing activities:
Proceeds from Term Loan	450,000		275,000
Proceeds from Delayed Draw Term Loan					18,000
Repayments of term loans	(1,125)		(472,742)	(3,375)	(4,545)
Proceeds from revolving credit facility				25,000	25,000
Payment of contingent consideration			(1,500)
Repayments on Revolving Line of Credit					(25,000)
Payment of debt issuance costs	(14,255)		(3,511)		(225)
Proceeds from equity offering, net of underwriting discounts			452,812
Repurchase of outstanding equity / Definitive OpCo units			(92,812)
Payments of IPO issuance costs			(5,913)
Member contributions	696,991		5,500		6,365
Member distributions	(6,492)	(468)	(7,139)	(2,109)	(2,940)
Net cash provided by financing activities	1,125,119	(468)	149,695	19,516	16,655
Net increase in cash and cash equivalents	8,618	(2,301)	165,026	26,064	16,010
Effect of exchange rate changes on cash and cash equivalents			(48)		146
Cash and cash equivalents, beginning of period	17,058	19,359	24,774	8,618	8,618
Cash and cash equivalents, end of period	8,618	17,058	189,752	34,682	24,774
Cash paid during the year for:
Cash paid for interest	9,939	277	27,587	$ 23,043	25,958
Cash paid for income taxes	0	60	13		0
Supplemental disclosure of non-cash investing activities:
Accrued purchases of data	0	0			3,389
Net decrease in accrued capital expenditures, including purchases of data			(3,020)
Supplemental disclosure of non-cash financing activities:
Increase in unpaid public offering costs			$ 5,481
Acquisitions:
Net assets acquired, net of cash acquired	1,689,395	29,831			43,571
Capital contribution	(574,263)	0			(25,439)
Contingent consideration	0	0			(2,600)
Consideration paid to former members included in accrued expenses	(6,935)	0			6,935
Net cash paid	$ 1,108,197	$ 29,831			$ 22,467

Organization

Organization	May 24, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	1. Organization Definitive Healthcare Corp. (the “Corporation”) was organized as a Delaware corporation on May 5, 2021 and its shares were funded at May 24, 2021. The Corporation’s fiscal year end is December 31. Pursuant to a reorganization into a holding corporation structure, the Corporation will become a holding corporation and its sole assets are expected to be an equity interest in AIDH TopCo, LLC. The Corporation will be the sole managing member of AIDH TopCo, LLC, and will operate and control all of the businesses and affairs of AIDH TopCo, LLC and, through AIDH TopCo, LLC and its subsidiaries, continue to conduct the business now conducted by these entities.

Description of Business

Description of Business	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Accounting Policies [Abstract]
Description of Business	1. Description of Business Definitive Healthcare Corp. (together with its subsidiaries, “Definitive Healthcare” or the “Company”), through its operating subsidiary, AIDH TopCo, LLC (“Definitive OpCo”), provides comprehensive and up-to-date . On October 27, 2020, Definitive OpCo completed the purchase of all of the outst a Business Combinations Organization Definitive Healthcare Corp. was formed on May 5, 2021 as a Delaware corporation for the purposes of facilitating an initial public offering (“IPO”) and other related transactions in order to carry on the business of Definitive OpCo, a Delaware limited liability company. Following consummation of the Reorganization Transactions, Definitive OpCo became an indirect subsidiary of Definitive Healthcare Corp. The Company is headquartered in Framingham, MA, with three other offices in the United States and one in Sweden. Initial Public Offering On September 17, 2021, Definitive Healthcare completed its IPO, in which it sold 17,888,888 shares of Class A Common Stock (including shares issued pursuant to the exercise in full of the underwriters’ option to purchase additional shares) at a public offering price of $27.00 per share for net proceeds of $452.8 million, after deducting underwriters’ discounts and commissions Reorganization Transactions In connection with the IPO, the Company completed the following transactions (the “Reorganization Transactions”). Definitive OpCo entered into an amended and restated limited liability company agreement (the “Amended LLC Agreement”) pursuant to which members of Definitive OpCo prior to the IPO who continue to hold LLC Units, have the right to require Definitive OpCo to exchange all or a portion of their LLC Units for newly issued shares of Class A Common Stock. Entities treated as corporations for U.S. tax purposes that hold LLC Units (individually, a “Blocker Company” and collectively, the “Blocker Companies”) each merged with a merger subsidiary and subsequently merged into Definitive Healthcare Corp. Except for AIDH Management Holdings, LLC, members of AIDH Management Holdings, LLC, received a number of shares of Definitive Healthcare Corp. Class B Common Stock with no par value per share. The total shares of Class B Common Stock outstanding is equal to the number of LLC Units outstanding. AIDH Management Holdings, LLC is a special purpose investment vehicle through which certain persons, primarily our employees and certain legacy investors, indirectly hold interests in Definitive OpCo; the holders of interests in AIDH Management Holdings, LLC received a number of shares of Definitive Healthcare Corp. Class B Common Stock. In connection with the Reorganization Transactions and Definitive Income Taxes	1. Description of Business AIDH TopCo, LLC (together with its subsidiaries, “AIDH TopCo” or the “Company”), is a Delaware limited liability company that was formed by investment funds affiliated with Advent International Corporation (“Advent”, the “Sponsor”) for the purpose of acquiring Definitive Healthcare Holdings, LLC (“Definitive Holdco”) and its subsidiary Definitive Healthcare LLC (“Definitive”). On July 16, 2019, AIDH Buyer, LLC (“AIDH Buyer”), a wholly owned subsidiary of the Company, acquired 100% of the issued and outstanding units of Definitive Holdco for $1.7 billion (the “Definitive Holdco Acquisition”). Refer to Note 3. Business Combinations References to “Successor” or “Successor Company” relate to the financial position and results of operations of the Company after the Definitive Holdco Acquisition. References to “Predecessor” or “Predecessor Company” refer to the financial position and results of operations of the legacy Definitive Holdco. Definitive Holdco was formed in 2015 for the purpose of acquiring Definitive, which was founded in 2011 to provide healthcare commercial intelligence that enables all companies that compete within or sell into the healthcare ecosystem to be more successful. The Company provides comprehensive and up-to-date The Company’s headquarters are located in Framingham, MA, with operations in three offices throughout the United States and one office in Sweden. On January 16, 2019, Definitive acquired substantially all of the assets and assumed substantially all of the liabilities of HIMSS Analytics, LLC (“HIMSS”). Refer to Note 3. Business Combinations On December 2, 2019, the Company acquired all of the outstanding common and preferred stock of Healthcare Sales Enablement, Inc. (“HSE”). Refer to Note 3. Business Combinations On October 27, 2020, the Company completed the purchase of all of the outstanding shares of Monocl, a cloud-based platform with millions of expert profiles. Refer to Note 3. Business Combinations

Summary of Significant Accounti

Summary of Significant Accounting Policies	May 24, 2021	Sep. 30, 2021	Dec. 31, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Polici e Basis of Accounting The Balance Sheet has been prepared in accordance with generally accepted accounting principles in the United States (“U.S. GAAP”). Separate statements of operations, changes in stockholders’ equity and cash flows have not been presented in the financial statement because there have been no activities in this entity or because the single transaction is fully disclosed below.	2. Summary of Significant Accounting Basis of Presentation The accompanying unaudited condensed consolidated statements Refer to Note 2. Summary of Significant Accounting Adoption of Recently Issued Financial Accounting Standards In August 2018, the FASB issued ASU No. 2018-15— Intangibles — Goodwill and Other — Internal-Use 350-40), internal-use impact Recently-Issued Accounting Pronouncements Not Yet Adopted In February 2016, the FASB issued ASU 2016-02— Leases recording a cumulative effect adjustment as of the adoption date, with certain practical expedients available. The Company, as an Emerging Growth Company as defined by the Jumpstart Our Business Startups Act of 2012 (the “JOBS Act”), can elect to take the extended transition period and adopt the standard following guidance for non-public The Company will adopt ASU 2016-02 2018-11, non-lease . In June 2016, the FASB issued ASU No. 2016-13— Financial Instruments Credit Losses (Topic 326) Measurement of Credit Losses on Financial Instruments In December 2019, the FASB issued ASU No. 2019-12— Income Taxes (Topic 740), Simplifying the Accounting for Income Taxes. In March 2020, the FASB issued ASU No. 2020-04— Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting No. 2020-04	2. Summary of Significant Accounting Policies Basis of Presentation The consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”). The Financial Accounting Standards Board (“FASB”) establishes these principles to ensure financial condition, results of operations, and cash flows are consistently reported. Any reference in these notes to applicable accounting guidance is meant to refer to the authoritative nongovernmental GAAP as found in the FASB Accounting Standards Codification (“ASC”). Principles of Consolidation The consolidated financial statements include the accounts of the Company and its consolidated subsidiaries. All significant intercompany accounts and transactions have been eliminated in consolidation. Use of Estimates in the Preparation of Financial Statements The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates, judgements, and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements, as well as the reported amounts of revenues and expenses during the reporting period. These estimates relate, but are not limited to, revenue recognition, allowance for doubtful accounts, contingencies, valuations and useful lives of intangible assets acquired in business combinations, equity-based compensation, and income taxes. Actual results could differ from those estimates. Revenue Recognition The Company derives revenue primarily from subscription license fees charged for access to the Company’s database platform, and professional services. The customer arrangements include a promise to allow customers to access subscription license to the database platform which is hosted by the Company over the contract period, without allowing the customer to take possession of the subscription license or transfer hosting to a third party. The Company recognizes revenue in accordance with ASC 606– Revenue from Contracts with Customers Revenue related to hosted subscription license arrangements, which often include non-distinct non-cancellable. The Company also enters into a limited number of contracts that can include various combinations of professional services, which are generally capable of being distinct and can be accounted for as separate performance obligations. Revenue related to these professional services is insignificant and is recognized at a point in time, when the performance obligations under the terms of the contract are satisfied and control has been transferred to the customer. When a contract contains multiple performance obligations, the contract transaction price is allocated on a relative standalone selling price (“SSP”) basis to each performance obligation. The Company typically determines SSP based on observable selling prices of its products and services. In instances where SSP is not directly observable, SSP is determined using information that may include market conditions and other observable inputs, or by using the residual approach. The Company accounts for an arrangement when it has approval and commitment from both parties, the rights are identified, the contract has commercial substance, and collectability of consideration is probable. The Company generally obtains written purchase contracts from its customers for a specified service at a specified price, with a specified term, which constitutes an arrangement. Revenue is recognized at the amount expected to be collected, net of any taxes collected from customers, which are subsequently remitted to governmental authorities. The timing of revenue recognition may not align with the right to invoice the customer, but the Company has determined that in such cases, a significant financing component generally does not exist. The Company has elected the practical expedient that permits an entity not to recognize a significant financing component if the time between the transfer of a good or service and payment is one year or less. Payment terms on invoiced amounts are typically 30 days. The Company does not offer rights of return for its products and services in the normal course of business, and contracts generally do not include customer acceptance clauses. The Company arrangements typically do not contain variable consideration. However, certain contracts with customers may include service level agreements that entitle the customer to receive service credits, and in certain cases, service refunds, when defined service levels are not met. These arrangements represent a form of variable consideration, which is considered in the calculation of the transaction price. The Company estimates the amount of variable considerations at the expected value based on its assessment of legal enforceability, anticipated performance and a review of specific transactions, historical experience and market and economic conditions. The Company historically has not experienced any significant incidents that affected the defined levels of reliability and performance as required by the contracts. Fair Value Measurements The Company measures assets and liabilities at fair value based on an expected exit price, which represents the amount that would be received on the sale of an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value may be based on assumptions that market participants would use in pricing an asset or liability. The authoritative guidance on fair value measurements establishes a consistent framework for measuring fair value on either a recurring or nonrecurring basis whereby inputs, used in valuation techniques, are assigned a hierarchical level as follows: Level 1 - Observable inputs that reflect unadjusted quoted prices in active markets for identical assets or liabilities Level 2 - Other inputs that are directly or indirectly observable in the marketplace Level 3 - Unobservable inputs that are supported by little or no market activity, including the Company’s own assumptions in determining fair value. Cash and Cash Equivalents The Company considers all short-term, highly liquid investments with an original maturity of three months or less to be cash and cash equivalents. Concentration of Credit Risk and Significant Customers Financial instruments that potentially subject the Company to concentrations of credit risk consist principally of cash and cash equivalents and accounts receivable. The Company holds cash at major financial institutions that often exceed Federal Deposit Insurance Corporation (“FDIC”) insured limits. The Company manages its credit risk associated with cash concentrations by concentrating its cash deposits in high quality financial institutions and by periodically evaluating the credit quality of the primary financial institutions holding such deposits. The carrying value of cash approximates fair value. Historically, the Company has not experienced any losses due to such cash concentrations. The Company does not have any off-balance-sheet Concentrations of credit risk with respect to trade account receivables are limited due to the large number of customers comprising the Company’s customer base. No single customer accounted for more than 10% of total net sales or accounts receivable in 2020 and 2019. Accounts Receivable, Net and Contract Assets Accounts receivable are stated at the amount management expects to collect from outstanding balances. Allowances for doubtful accounts are provided for those outstanding balances considered to be uncollectible based upon historical collection experience, changes in customer payment profiles, the aging of receivable balances, and management’s overall evaluation of the outstanding balances at year end. Balances that are still outstanding after management has made reasonable collection efforts are written off through a charge to the allowance for doubtful accounts. At December 31, 2020 and 2019, the allowance for doubtful accounts was $0.9 million and $0.5 million, respectively. Contract assets represent contractual rights to consideration in the future and are generated when contractual billing schedules differ from the timing of revenue recognition. The Company records accounts receivable when it has the unconditional right to issue an invoice and receive payment regardless of whether revenue has been recognized. If revenue is recognized in advance of the right to invoice, a contract asset (unbilled receivable) is recorded, which is included in accounts receivable, net in the consolidated balance sheet. Deferred Contract Costs Certain sales commissions earned by the Company’s employees are considered incremental and recoverable costs of obtaining a contract with a customer. These sales commissions for initial and renewal contracts are capitalized and are included in current portion of deferred contract costs and deferred contract costs, net of current portion. Capitalized amounts also include the associated payroll taxes and other fringe benefits associated with the payments to the Company’s employees. Costs capitalized related to new revenue contracts are amortized on a straight-line basis over four years, which reflects the average period of benefit, including expected contract renewals. When determining the period of benefit, the Company primarily considered its initial estimated customer life, the technological life of the subscription license, as well as an estimated customer relationship period. Costs capitalized related to renewal contracts are amortized on a straight-basis over 2 years, which reflects the average renewal period. Renewal contracts with a term of one year or less are expensed. The capitalized amounts are recoverable through future revenue streams under all non-cancellable Property and Equipment, Net Property and equipment are stated at cost, net of accumulated depreciation and amortization. The assets are depreciated on a straight-line basis over the estimated useful lives as follows: Furniture and equipment 5 years Computers and software 3 years Leasehold improvements Lesser of the asset life or lease term Upon retirement or sale, the cost of assets disposed and the related accumulated depreciation are removed from the accounts and any resulting gain or loss is recognized as gain or loss on disposal of assets in the consolidated statements of income (loss). Major replacements and improvements are capitalized, while general repairs and maintenance are charged to expense as incurred. Advertising and Promotional Expenses The Company expenses advertising costs as incurred in accordance with ASC 720— Other Expenses – Advertising Cost Software Development Costs The Company accounts for its software development costs in accordance with the guidance set forth in ASC 350-40, Intangibles – Goodwill and Other – Internal Use Software. Business Combinations The Company accounts for business combinations using the acquisition method in accordance with ASC 805, Business Combinations The estimates are inherently uncertain and subject to revision as additional information is obtained during the measurement period for an acquisition, which may last up to one year from the acquisition date. During the measurement period, the Company may record adjustments to the fair value of tangible and intangible assets acquired and liabilities assumed, with a corresponding offset to goodwill. After the conclusion of the measurement period or the final determination of the fair value of assets acquired or liabilities assumed, whichever comes first, any subsequent adjustments are recorded to earnings. In addition, uncertain tax positions and tax-related For any given acquisition, the Company may identify certain pre-acquisition Goodwill and Intangible Assets Goodwill is calculated as the excess of the purchase consideration paid in the acquisition of a business over the fair value of the identifiable assets acquired and liabilities assumed. Goodwill is not amortized and is tested for impairment at the reporting unit level, at least annually, and more frequently if events or circumstances occur that would indicate a potential decline in fair value. A reporting unit is an operating segment or a component of an operating segment. The Company first assesses qualitative factors to evaluate whether it is more likely than not that the fair value of a reporting unit is less than the carrying amount, or it may elect to bypass such assessment. If it is determined that it is more likely than not that the fair value of the reporting unit is less than its carrying value, or if the Company elects to bypass the qualitative assessment, management will perform a quantitative test by determining the fair value of the reporting unit. The estimated fair value of the reporting unit is based on a projected discounted cash flow model that includes significant assumptions and estimates, including the discount rate, growth rate, and future financial performance. Valuations of similarly situated public companies are also evaluated when assessing the fair value of the reporting unit. If the carrying value of the reporting unit exceeds the fair value, then a goodwill impairment loss is recognized for the difference. The Company performs its annual impairment assessment in the first month of the fourth quarter of each calendar year. Definite-lived intangible assets are amortized over their estimated useful lives, Customer relationships 14 – 15 years Technology 7 – 8 years Tradenames / trademark 17 – 19 years Data 1– 4 years Impairment of Long-Lived Assets The Company reviews the carrying value of property and equipment and other long-lived assets, including definite-lived intangible assets and property and equipment, for impairment whenever events and circumstances indicate that the carrying value of an asset may not be recoverable. If estimated undiscounted future cash flows expected to result from its use and eventual disposition are not expected to be adequate to recover the asset’s carrying value, an impairment charge is recorded for the excess of the asset’s carrying value over its estimated fair value. Deferred Revenue Deferred revenue consists of customer payments and billings in advance of revenue being recognized from the subscription services. If revenue has not yet been recognized, a contract liability (deferred revenue) is recorded. Deferred revenue that is anticipated to be recognized within the next 12 months is recorded as current portion of deferred revenue and the remaining portion is included in deferred revenue on the consolidated balance sheets. Debt Issuance Costs Costs incurred in connection with the issuance of long-term debt are deferred and amortized as interest expense over the terms of the related debt using the effective interest method for term debt and on a straight-line basis for revolving debt. To the extent that the debt is outstanding, these amounts are reflected in the consolidated balance sheets as direct deductions from the long-term portions of debt, except for the costs related to the Company’s revolving credit facilities, which are presented as a non-current non-revolving Deferred Initial Public Offering Costs The Company capitalizes deferred initial public offering (“IPO”) costs, which primarily consist of direct, incremental legal, professional, accounting and other third-party fees relating to the Company’s initial public offering, within other non-current Sales Tax The Company’s revenues may be subject to local sales taxes in certain states, if applicable. It is the Company’s policy to treat all such taxes on a “net” basis, which means the charges for sales taxes to the Company’s customers are not included in revenues and the remittance of such taxes is not presented as an expense. Income Taxes AIDH TopCo, LLC is taxed as a partnership. Definitive Healthcare Holdings, LLC is a wholly owned subsidiary of AIDH TopCo, LLC and is treated as a disregarded entity for income tax purposes. Accordingly, for federal and state income tax purposes, income, losses, and other tax attributes not generated by the HSE or Monocl subsidiaries pass through to the AIDH TopCo, LLC members’ income tax returns. The Company may be subject to certain taxes on behalf of its members in certain states. Definitive Healthcare Holdings was not subject to any federal income taxes for the tax years ended December 31, 2020 and 2019, nor was it subject to state income taxes in certain jurisdictions for the tax years ended December 31, 2020 and 2019. HSE and the Monocl US subsidiaries are taxed as corporations. Accordingly, these entities account for income taxes by recognizing tax assets and liabilities for the cumulative effect of all the temporary differences between financial statement carrying amounts and the tax basis of assets and liabilities. The foreign tax provision pertains to foreign income taxes due at the Swedish Monocl subsidiaries. Deferred taxes for the HSE, Monocl US and Swedish subsidiaries are determined using enacted federal, state, or foreign income tax rates in effect in the year in which the differences are expected to reverse. Valuation allowances are provided if based upon the weight of available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. The Company has provided for these taxes. The aggregate of such taxes is not material and is included in general and administrative in the accompanied statement of operations. Under the provisions of ASC 740 , Income Taxes Net Loss Per Unit Net income or loss per unit is computed in conformity with the two-class two-class two-class Basic net income or loss per unit is computed by dividing the net income or loss by the weighted-average number of common units of the Company outstanding during the period. Diluted net income or loss per unit is computed by giving effect to all potential units of common units, including outstanding incentive units, to the extent dilutive. The Company uses the treasury stock method to calculate potentially dilutive shares, as if they were converted into common stock at the beginning of the period. Basic and diluted net income or loss per unit was the same for each period presented as the inclusion of all potential units of common units outstanding would have been anti-dilutive. All net earnings (loss) for the Predecessor period from January 1, 2019 to July 15, 2019 were entirely allocable to Predecessor members. Additionally, due to the impact of the Definitive Holdco Acquisition, the Company’s capital structure for the Predecessor and Successor periods is not comparable. As a result, the presentation of earnings (loss) per share for the periods prior to such transaction is not meaningful and only earnings (loss) per unit for periods subsequent to the Definitive Holdco Acquisition are presented herein. See Note 16. Net Loss Per Unit Equity-based Compensation The Company periodically grants equity units to employees, consultants, directors, managers, or others providing service. These units are considered profit interests, which in general, entitle the holder of the unit to a pro rata share of the increase in fair value of the unit over the base value, which is determined at the award date, and are deemed to be equity instruments. Certain units have time-based and performance-based vesting criteria. The Company accounts for these profit interest units in accordance with ASC 718— Compensation – Stock Compensation. The Company classifies equity-based compensation expense in its consolidated statements of (loss) income in the same manner in which the award recipient’s salary and related costs are classified. Adoption of Recently Issued Financial Accounting Standards In May 2014, the FASB issued ASC 606— Revenue from Contracts with Customers 340-40, Other Assets and Deferred Costs – Contracts with Customers The Company adopted ASC 606 effective January 1, 2019 under the modified retrospective method, which resulted in an adjustment at January 1, 2019 of $5.4 million to members’ capital for the cumulative effect of applying the standard to all contracts not completed as of the adoption date. The adjustment primarily related to deferred contract costs, including incremental employee sales commissions and other employee compensation arrangements, and adjustments to deferred and unbilled revenues of $4.3 million and $1.1 million, respectively. The cost of all incremental commissions and other employee compensation arrangements are deferred and amortized on a straight-line basis over the expected period of benefit, generally between two and four years. The deferred and unbilled revenues were adjusted upon adoption to better align the recognition of revenues with the timing of transfer of control to the customer. The cumulative effect of applying the new guidance was recorded as an adjustment to members’ capital as of the adoption date. As a result of applying the modified retrospective method to adopt the new revenue guidance, the following adjustments were made to the consolidated balance sheet as of January 1, 2019. As reported ASC 606 As Adjusted Consolidated Balance Sheet: Accounts receivable, net $ 14,932 $ 367 $ 15,299 Current portion of deferred contract costs — 1,346 1,346 Total current assets 35,176 1,713 36,889 Deferred contract costs, net of current portion — 2,973 2,973 Total assets $ 87,061 $ 4,686 $ 91,747 Current portion of deferred revenue 32,187 (729 ) 31,458 Total current liabilities 36,676 (729 ) 35,947 Total liabilities 36,676 (729 ) 35,947 Members’ capital 50,385 5,415 55,800 Total liabilities and members’ capital $ 87,061 $ 4,686 $ 91,747 The following tables compare the reported consolidated balance sheet as of December 31, 2019 and statements of (loss) income for the periods from July 16, 2019 to December 31, 2019 and January 1, 2019 to July 15, 2019, to the adjusted amounts had ASC 605 , As Reported Adjustments As Adjusted Consolidated Balance Sheet: Accounts receivable, net $ 25,021 $ (250 ) $ 24,771 Current portion of contract assets 769 (769 ) — Total current assets 36,107 (1,019 ) 35,088 Contract assets, net of current portion 2,116 (2,116 ) — Total assets 1,721,154 (3,135 ) 1,718,019 Current portion of deferred revenue 45,977 990 46,967 Total current liabilities 69,917 990 70,907 Total liabilities 504,914 990 505,904 Members’ capital (deficit) 1,216,240 (4,125 ) 1,212,115 Total liabilities and members’ capital (deficit) $ 1,721,154 $ (3,135 ) $ 1,718,019 Predecessor Company As Reported Period from January 1, Adjustments As Adjusted Period from January 1, Revenue $ 45,458 $ (79 ) $ 45,379 Total cost of revenue 5,328 — 5,328 Gross profit 40,130 (79 ) 40,051 Sales and marketing 16,039 1,416 17,455 Total operating expenses 27,097 1,416 28,513 Income (loss) from operations 13,033 (1,495 ) 11,538 Total other expense, net (165 ) — (165 ) Net income (loss) $ 12,868 $ (1,495 ) $ 11,373 Successor Company As Reported Period from July 16, 2019 to December 31, 2019 Adjustments As Adjusted Period from July 16, 2019 to December 31, Revenue $ 40,045 $ (66 ) $ 39,979 Total cost of revenue 13,282 — 13,282 Gross profit 26,763 (66 ) 26,697 Sales and marketing 10,814 2,885 13,699 Total operating expenses 57,825 2,885 60,710 Loss from operations (31,062 ) (2,951 ) (34,013 ) Total other expense, net (18,204 ) — (18,204 ) Net loss $ (49,266 ) $ (2,951 ) $ (52,217 ) In January 2017, the FASB issued ASU No. 2017-04 —Goodwill and Other (Topic 350) – Simplifying the Test for Goodwill Impairment. 2017-04 In June 2018, the FASB issued ASU No. 2018-07 —Compensation—Stock Compensation (Topic 718), Improvements to Nonemployee Share-based Payment Accounting Recently-Issued Accounting Pronouncements Not Yet Adopted In February 2016, the FASB issued ASU 2016-02— Leases right-of-use In June 2016, the FASB issued ASU No. 2016-13 —Financial Instruments—Credit Losses (Topic 326)—Measurement of Credit Losses on Financial Instruments. In August 2018, the FASB issued ASU No. 2018-15— Intangibles—Goodwill and Other—Internal-Use 350-40), implementation costs incurred to develop or obtain internal-use In December 2019, the FASB issued ASU No. 2019-12— Income Taxes (Topic 740), Simplifying the Accounting for Income Taxes In March 2020, the FASB issued ASU No. 2020-04— Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting No. 2020-04

Business Combinations

Business Combinations	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Business Combinations [Abstract]
Business Combinations	3. Business Combinations On October 27, 2020, the Company completed the purchase of all outstanding shares of Monocl for a total estimated consideration of $46.3 million , summarized as follows: (in thousands) Cash consideration $ 18,307 Equity issuance 25,439 Contingent consideration 2,600 Purchase price $ 46,346 The assets acquired and liabilities assumed were recorded at their estimated fair values and the results of operations were included in the Company’s consolidated results as of the acquisition date. The contingent consideration performance targets for earnout payments are based on the contractual Annual Recurring Revenue (“ARR”) for each of the twelve-month periods ending December 31, 2020 and December 31, 2021. Potential payouts range from The Company estimated the fair value of contingent consideration to be $6.9 million and $5.2 million at September 30, 2021 and December 31, 2020, respectively, based on the achievement of 2020 ARR targets and the probability of achieving the 2021 targets. Refer to Note 9. Fair Value Measurements The purchase accounting for the Monocl acquisition was finalized as of December 31, 2020. The fair values assigned to tangible and identified intangible assets acquired and liabilities assumed were based on management’s estimates and assumptions. The final allocation of the acquisition-date fair values of assets and liabilities as of December 31, 2020, was as follows: (in thousands) Preliminary allocation: October 27, Cash $ 2,774 Accounts receivable 788 Prepaid expenses and other current assets 614 Property and equipment 20 Intangible assets 18,900 Accounts payable and accrued expenses (2,137 ) Deferred revenue (2,884 ) Total assets acquired and liabilities assumed 18,075 Goodwill 28,271 Purchase price $ 46,346 T Customer relationships represent the estimated fair value of the underlying relationships with the acquired entity’s business customers and are amortized using the annual pattern of cash flows (economic value method) over the estimated 14-year Data includes proprietary data on medical and scientific expert personnel. The technology recognized includes Monocl’s existing technology and provides users with a cloud-based platform with millions of expert profiles generated using machine learning and tailored algorithms through an online platform. This technology provides the automated collection of content sources, data processing and augmentation, and ultimately the generation of contextually relevant and continuously updated expert profiles. The trademark represents the estimated fair value of the registered trademarks, logo and domain names associated with the Monocl corporate brand. The data, technology, and trademark are amortized using the straight-line method over the estimated remaining useful life of 3 years, 8 years, and 19 years, respectively. In connection with the acquisition, the Company recognized acquisition related costs of $0.4 million which were recorded within transaction expenses in the accompanying consolidated statements of income (loss) . The results of operations of Monocl are included in the Company’s consolidated results since the date of acquisition. The revenue and net loss of Monocl reflected in the consolidated statements of operations for the year ended December 31, 2020 were $1.2 million and $1.6 million, respectively. Unaudited Pro Forma Supplementary Data: Nine Months Ended (in thousands) Revenue $ 91,750 Net loss (43,763 ) The pro forma net loss includes adjustments to amortization expense for the valuation of other intangible assets of $0.6 million and interest expense related to incremental borrowings used to finance the transaction of $0.8 million and for the nine months ended September 30, 2020. The unaudited pro forma supplementary data is provided for informational purposes only and should not be construed to be indicative of the Company’s results of operations had the acquisition been consummated on the date assumed or of the Company’s results of operations for any future date.	3. Business Combinations On October 27, 2020, the Company completed the purchase of all of the outstanding shares of Monocl Holding Company (“Monocl”), a cloud-based platform with millions of expert profiles, for a total estimated consideration of $46.3 million and up to $60.0 million, consisting of approximately $18.3 million of cash payable at closing, $25.4 million of rollover equity, and up to $15.0 million of contingent consideration. The contingent consideration, which relates to earn-out The consideration transferred for the transaction is summarized as follows (in thousands): Cash consideration $ 18,307 Equity issuance 25,439 Contingent consideration 2,600 Purchase price $ 46,346 Cash consideration for the acquisition was primarily provided through borrowings under the Company’s credit facility. The performance targets for the contingent consideration are based on the Annual Recurring Revenue (“ARR”), measured as annually contractual recurring revenue for each of the twelve-month periods ending December 31, 2020 and December 31, 2021. Potential payouts range from $0 to $5.0 million and $0 to $10 million based on ARR of below $8.5 million to over $9.5 million and below $12.0 million to over $16.0 million for each of the twelve month periods ending December 31, 2020 and 2021, respectively. The Company estimated the fair value of the contingent consideration to be $5.2 million at December 31, 2020 based on the achievement of Annual 2020 ARR targets and the probability of achieving the 2021 targets. Refer to note 9. Fair Value Measurements for more detail. The purchase accounting for the Monocl acquisition was finalized as of December 31, 2020. The final allocation of the acquisition-date fair values of assets and liabilities pertaining to this business combination as of December 31, 2020, was as follows (in thousands): October 27, 2020 Cash $ 2,774 Accounts receivable 788 Prepaid expenses and other current assets 614 Property and equipment 20 Intangible assets 18,900 Accounts payable and accrued expenses (2,137 ) Deferred revenue (2,884 ) Total assets acquired and liabilities assumed 18,075 Goodwill 28,271 Purchase price $ 46,346 As a result of the Monocl acquisition, the Company recorded goodwill, customer relationships, data, technology, and trademark of $28.3 million, $11.9 million, $3.0 million, $2.6 million and $1.4 million, respectively, as of the acquisition date. The goodwill recognized includes the fair value of the assembled workforce, which is not recognized as an intangible asset separable from goodwill, and any expected synergies gained through the acquisition. The Company determined that the goodwill resulting from the acquisition is not deductible for tax purposes. In connection with the acquisition, the Company also recorded deferred revenue of $2.9 million and a contingent consideration liability of $2.6 million. See Note 9. Fair Value Measurements Customer relationships represent the estimated fair value of the underlying relationships with the acquired entity’s business customers. The Company valued customer relationships using the income approach, specifically the excess earnings method. Significant assumptions include forecast of revenues, cost of revenues, estimated attrition rates, and discount rates reflecting the different risk profiles of the asset depending upon the acquisition. The value assigned to customer relationships is $11.9 million and is amortized using the annual pattern of cash flows (economic value method) over the estimated 14-year Data includes proprietary data on medical and scientific expert personnel. The Company used the cost approach, specifically the replacement cost method to value the data. The Fair value of the data was estimated to be $3.0 million and is amortized using the straight-line method over the estimated remaining useful life of 3 years. The technology recognized includes Monocl’s existing technology and provides users with a cloud-based platform with millions of expert profiles generated using machine learning and tailored algorithms through an online platform. This technology provides the automated collection of content sources, data processing and augmentation, and ultimately the generation of contextually relevant and continuously updated expert profiles. The Company used the income approach, specifically the relief-from-royalty method, to determine the value of technology, which was valued at $2.6 million and is amortized using the straight-line method over the estimated remaining useful life of 8 years. The trademark represents the estimated fair value of the registered trademarks, logo and domain names associated with the Monocl corporate brand. The Company estimated the fair value of the trademark using a relief from royalty method. Significant assumptions include forecast of royalty rate, company revenues, tax rate, and discount rate. The trademark was valued at $1.4 million and is amortized using the straight-line method over the estimated remaining useful life of 19 years. The weighted average amortization period for the customer relationships, tradenames, technology, and data is 15 years, 17 years, 8 years and 3 years, respectively. See Note 7 for the estimated total intangible amortization expense during the next five years. In connection with the acquisition, the Company recognized acquisition related costs of $0.4 million which were recorded within transaction expenses in the accompanying consolidated statements of income (loss). The net loss of Monocl is included in the Company’s consolidated results since the date of acquisition. The revenue and net loss of Monocl reflected in the consolidated statements of income (loss) for the year ended December 31, 2020 (Successor) were $1.2 million and $1.6 million, respectively. Unaudited Pro Forma Supplementary Data (in thousands) Year Ended Year Ended Revenue $ 122,333 $ 87,157 Net loss (58,350 ) (97,134 ) The unaudited pro forma supplementary data presented in the table above shows the effect of the Monocl and Definitive Holdco Acquisitions, as if the transactions had occurred at the beginning of fiscal year 2019. The pro forma net loss includes adjustments to amortization expense for the valuation of other intangible assets of $0.8 million and $1.2 million and interest expense related to incremental borrowings used to finance the transaction of $1.0 million and $1.2 million for the years ended December 31, 2020 and 2019, respectively. Acquisition expenses of $0.4 million were excluded from the pro forma net loss for the year ended December 31, 2020 and included in the pro forma net loss for the year-ended December 31, 2019. The unaudited pro forma supplementary data is provided for informational purposes only and should not be construed to be indicative of the Company’s results of operations had the acquisition been consummated on the date assumed or of the Company’s results of operations for any future date. 2019 acquisitions Definitive Holdco (“Definitive Holdco Acquisition”) On July 16, 2019, Advent, our Sponsor, entered into an agreement with Definitive Holdco (the “Agreement”) to, among other things, acquire 100% of its issued and outstanding units, for a total consideration of $1,699.6 million, consisting of $1,129.3 million of cash and $570.3 million of equity units issued to the sellers and former owners. For purposes of the Agreement, affiliated legal entities of Advent include Advent IX Funds, AIDH Holdings, Inc. (“AIDH Holdings”), AIDH TopCo, AIDH Buyer, and AIDH Finance Sub, LLC (“AIDH Finance Sub”). Advent IX Funds owns 100% of the outstanding units of AIDH Holdings. AIDH Holdings owns 55% of the outstanding units of the Company, with the remaining interests (45%) issued to the prior owners of Definitive Holdco as rollover units. The Company owns 100% of outstanding units of AIDH Buyer. Upon acquisition, AIDH Buyer owns 100% of Definitive Holdco. The transactions outlined in the Agreement were executed as follows: 1. Debt Financing. Immediately prior to closing of the Agreement, AIDH Finance Sub, an affiliated legal entity of Advent, entered into debt financing agreements for a $450.0 million term loan payable (the “2019 Term Loan”), a $100.0 million delayed draw term loan payable (the “2019 Delayed Draw Term Loan”), and a $25.0 million revolving debt facility (the “2019 Revolving Debt Facility). See Note 8, for more detail. These financing agreements were collateralized by 100% of AIDH Finance Sub capital prior to the Finance Merger, defined below. 2. Finance Merger. Upon closing the Agreement, AIDH Finance Sub was merged with Definitive Holdco (surviving entity). After the merger, the financing agreements were collateralized by 100% of AIDH Buyer and Definitive Holdco units. 3. Distribution and Purchase of Units. Immediately after the Finance Merger, net proceeds from the debt financing (approximately $432.4 million) were paid to the prior owners of Definitive Holdco. Additionally, AIDH Buyer distributed $1,267.3 million (cash of $697.0 million and rollover equity of $570.3 million in the Company) as purchase consideration for all outstanding units of Definitive Holdco. The consideration transferred for the transaction is summarized as follows (in thousands): Cash consideration $ 1,129,346 Common units issued 570,266 Purchase price $ 1,699,612 Of the total cash consideration, $1,122.4 million was paid upon closing and $6.9 million in July 2020. Cash consideration for the acquisition was partly provided by net proceeds from the 2019 Term Loan, as outlined above. The purchase accounting for the Definitive Holdco Acquisition, was finalized as of July 16, 2020. The final allocation of the acquisition-date fair values of assets and liabilities pertaining to this business combination as of July 16, 2020, was as follows (in thousands). Predecessor Successor Company Carrying Fair Value Final Cash $ 17,058 $ — $ 17,058 Accounts receivable 12,747 — 12,747 Deferred contract costs 5,735 (5,735 ) — Prepaid expenses and other current assets 1,539 150 1,689 Other assets 49 — 49 Property and equipment 2,201 — 2,201 Intangible assets 19,108 456,292 475,400 Accounts payable and accrued expenses (5,477 ) 684 (4,793 ) Deferred revenue (38,278 ) 6,278 (32,000 ) Total assets acquired and liabilities assumed 14,682 457,669 472,351 Goodwill $ 82,767 $ 1,144,494 1,227,261 Total purchase price $ 1,699,612 The adjustments set forth in the following consolidated balance sheet as of July 15, 2019, reflect the effect of the Debt Financing and Finance Merger (reflected in the column “Debt Financing / Finance Merger”), and the fair value adjustments to assets acquired and liabilities assumed, as a result of the purchase accounting, in connection with the Definitive Holdco Acquisition (reflected in the column “Fair Value Adjustments”) (in thousands): Predecessor Debt Fair Value Successor July 16, 2019 Cash $ 17,058 $ — $ — $ 17,058 Accounts receivable 12,747 — — 12,747 Prepaid expenses and other current assets 1,539 16 150 1,705 Deferred contract costs 5,735 — (5,735 ) — Property and equipment 2,201 — — 2,201 Intangible assets 19,108 — 456,292 475,400 Goodwill 82,767 — 1,144,494 1,227,261 Other assets 49 14,589 — 14,638 Total assets $ 141,204 $ 14,605 $ 1,595,201 $ 1,751,010 Accounts payable and accrued expenses $ 5,477 $ 10,407 $ (684 ) $ 15,200 Deferred revenue 38,278 — (6,278 ) 32,000 Term Loan — 436,553 — 436,553 Total liabilities 43,755 446,960 (6,962 ) 483,753 Members’ Capital 97,449 (432,355 ) 1,602,163 1,267,257 Total liabilities and equity $ 141,204 $ 14,605 $ 1,595,201 $ 1,751,010 The Company recorded adjustments to goodwill of $1,144.5 million, and intangible assets of $456.3 million, as of the acquisition date of July 16, 2019, including adjustments to customer relationships, technology, tradenames and data of $340.8 million, $48.5 million, $32.7 million and $34.3 million, respectively. The goodwill recognized includes the fair value of the assembled workforce, which is not recognized as an intangible asset separable from goodwill, and any expected synergies gained through the acquisition. The Company determined that the goodwill resulting from the acquisition was in part deductible for tax purposes. The Company performed an ASC 805 fair valuation of the acquired identifiable intangible assets as of July 16, 2019. Key assumptions used to determine such fair values included growth rates, retention/attrition, research and development expenses, operating expenses, selling and marketing expenses, tax rates, royalty rates, obsolescence, utilization factors and others. Customer relationships represent the estimated fair value of the underlying relationships with the Company’s customers. The Company valued customer relationships using the income approach, specifically the excess earnings method. Significant assumptions include forecast of revenues, cost of revenues, estimated attrition rates, and discount rates reflecting the different risk profiles of the asset depending upon the acquisition. The value assigned to customer relationships is $358.0 million and is amortized using the annual pattern of cash flows (economic value method) over the estimated 15-year The technology recognized includes Definitive’s existing technology, which provides users access to in-depth up-to-date Tradenames includes the estimated fair value of the acquired registered trademarks, logo and domain names associated with the Definitive Healthcare corporate brand. The Company estimated the fair value of the trademark using a relief from royalty method. Significant assumptions include forecast of royalty rate, company revenues, tax rate, and discount rate. The trademark was valued at $34.1 million and is amortized using the straight-line method over the estimated remaining useful life of 22 years. Data includes proprietary data and insights on healthcare providers, including coverage of providers across the healthcare ecosystem from hospitals to physician groups to ambulatory surgery centers and accountable care organizations. The Company used the cost approach, specifically the replacement cost method to value the data. The Fair Value of the Data was estimated to be $34.8 million and is amortized using the straight-line method over the estimated remaining useful live of 3 years. The fair value of deferred revenue was estimated at $32.0 million, using the income approach, specifically the cost build-up The following table reconciles the purchase price to the capital contribution made by Sponsor as July 16, 2019 (in thousands): Total purchase price $ 1,699,612 Transaction costs paid from proceeds 4,004 Less Debt Financing 436,359 Capital Contribution $ 1,267,257 The results of Definitive Holdco are included in the Company’s consolidated results since the date of acquisition. The revenue of Definitive Holdco reflected in the consolidated statements of income (loss) for the year ended December 31, 2020 (Successor), period from July 16, 2019 to December 31, 2019 (Successor) and the period from January 1, 2019 to July 15, 2019 (Predecessor) was $116.9 million, $40.0 million and $45.5 million, respectively. The net (loss) income of Definitive Holdco, reflected in the consolidated statements of income (loss) for the year ended December 31, 2020 (Successor), period from July 16, 2019 to December 31, 2019 (Successor) and the period from January 1, 2019 to July 15, 2019 (Predecessor) was ($49.9 million), ($49.2 million) and $12.9 million, respectively. Unaudited Pro Forma Supplementary Data (in thousands) Year Ended Revenue $ 84,122 Net loss (92,228 ) The unaudited pro forma supplementary data presented in the table above shows the effect of the Definitive Holdco acquisition, as if the transaction had occurred at the beginning of fiscal year 2019. The pro forma net loss for the year-ended December 31, 2019 includes interest expense related to incremental borrowings used to finance the transaction of $21.0 million, adjustments to amortization expense for the valuation of other intangible assets of $33.4 million and fair value adjustments for deferred revenue of $1.4 million. The unaudited pro forma supplementary data is provided for informational purposes only and should not be construed to be indicative of the Company’s results of operations had the acquisition been consummated on the date assumed or of the Company’s results of operations for any future date. HIMSS On January 15, 2019, the Predecessor Company acquired substantially all of the assets and assumed substantially all of the liabilities of HIMSS for a total purchase price of $29.8 million. The Company recognized goodwill of $19.1 million, intangible assets of $11.4 million, accounts receivable of $1.3 million, and deferred revenue of $2.0 million, in connection with the acquisition. The acquisition was made to increase the Company’s market footprint. The goodwill recognized consisted largely of the estimated value of the assembled workforce and anticipated growth opportunities. The fair value of acquired intangible assets was determined using certain variations of the income approach and market approach. The estimated fair value of deferred revenue was based upon the applicable guidance and was calculated as the estimated cost for the Company to fulfill the contractual obligations plus a normal profit margin. The Company has included the financial results of HIMSS in the consolidated financial statements from the date of acquisition, which were not material. The transaction costs associated with the acquisition were not material. HSE On December 2, 2019, the Company acquired 100% of the issued and outstanding common and preferred stock of HSE for a total purchase price of $6.8 million, consisting of $2.8 million of cash and $4.0 million of equity issued. The Company recognized goodwill of $5.9 million, intangible assets of $1.2 million, deferred tax assets of $0.2 million, accounts receivable of $0.1 million, accounts payable of $0.3 million and deferred revenue of $0.3 million, in connection with the acquisition. The acquisition was made to increase the Company’s market footprint. The goodwill arising from the acquisition consists largely of the estimated value of the assembled workforce and anticipated growth opportunities. The fair value of acquired intangible assets was determined using certain variations of the income approach and market approach. The fair values of current assets and liabilities were based upon their historical costs at the date of acquisition due to their short-term nature. The estimated fair value of deferred revenue was based upon the applicable guidance and was calculated as the estimated cost for the Company to fulfill the contractual obligations plus a normal profit margin. The Company has included the financial results of HSE in the consolidated financial statements from the date of acquisition, which were not material. The transaction costs associated with the acquisition were not material.

Revenue

Revenue	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Revenue	4. Revenue The Company disaggregates revenue from its arrangements with customers by type of service as it believes these categories best depict how the nature, amount, timing, and uncertainty of revenue and cash flows are affected by economic factors. The following table represents a disaggregation of revenue from arrangements with customers for the nine months ended September 30, 2021 and 2020, respectively: Nine Months Ended (in thousands) 2021 2020 Platform subscriptions $ 118,545 $ 83,814 Professional services 1,296 845 Total revenue $ 119,841 $ 84,659 The opening and closing balances of the Company’s receivables, deferred contract costs and contract liabilities from contracts with customers are as follows: (in thousands) September 30, December 31, Accounts receivable, net $ 27,886 $ 33,108 Deferred contract costs 5,359 2,947 Long-term deferred contract costs 9,388 5,952 Deferred revenues 70,179 61,200 Deferred Contract Costs A summary of the activity impacting the deferred contract costs for the nine months ended September 30, 2021 and the year ended December 31, 2020 is presented below: (in thousands) September 30, December 31, Balance at beginning of period $ 8,899 $ 2,885 Costs amortized (3,195 ) (1,670 ) Additional amounts deferred 9,043 7,684 Balance at end of period 14,747 8,899 Classified as: Current 5,359 2,947 Non-current 9,388 5,952 Total $ 14,747 $ 8,899 Contract Liabilities A summary of the activity impacting deferred revenue balances during the nine months ended September 30, 2021 and for the year ended December 31, 2020 is presented below: (in thousands) September 30, December 31, Balance at beginning of period $ 61,200 $ 46,125 Revenue recognized (119,841 ) (118,317 ) Additional amounts deferred 128,820 133,392 Balance at end of period $ 70,179 $ 61,200 Remaining Performance Obligations ASC 606 introduced the concept of transaction price allocated to the remaining performance obligations of a contract, which is different than unbilled deferred revenue under ASC 605. Transaction price allocated to remaining performance obligations represents contracted revenue that has not yet been recognized, which includes unearned revenue and unbilled amounts that will be recognized as revenue in future periods. Transaction price allocated to remaining performance obligations is influenced by several factors, including seasonality, the timing of renewals, and disparate contract terms. Revenue allocated to remaining performance obligations represents contracted revenue that has not yet been recognized, which includes unearned revenue and backlog. The Company’s backlog represents installment billings for periods beyond the current billing cycle. The majority of the Company’s noncurrent remaining performance obligations will be recognized in the next 13 to 36 months . The remaining performance obligations consisted of the following: (in thousands) September 30, December 31, Current $ 128,653 $ 114,284 Non-current 78,900 58,250 Total $ 207,553 $ 172,534	4. Revenue The Company disaggregates revenue from its arrangements with customers by type of service as it believes these categories best depict how the nature, amount, timing, and uncertainty of revenue and cash flows are affected by economic factors. The following table represents a disaggregation of revenue from arrangements with customers for the year ended December 31, 2020 (Successor) and the periods from July 16, 2019 to December 31, 2019 (Successor) and January 1, 2019 to July 15, 2019 (Predecessor) (in thousands). Successor Company Predecessor Year Ended Period from Period from Platform subscriptions $ 117,080 $ 39,872 $ 45,244 Professional services 1,237 173 214 Total revenue $ 118,317 $ 40,045 $ 45,458 The opening and closing balances of the Company’s receivables, deferred contract costs and contract liabilities from contracts with customers are as follows (in thousands): Successor Company Predecessor December 31, December 31, July 16, July 15, January 1, Accounts receivables, net $ 33,108 $ 25,021 $ 12,747 $ 12,747 $ 15,299 Deferred contract costs 2,947 769 — 1,906 1,346 Long-term deferred contract costs 5,952 2,116 — 3,829 2,973 Deferred revenues $ 61,200 $ 46,125 $ 32,000 $ 38,278 $ 31,458 Deferred Contract Costs A summary of the activity impacting the deferred contract costs during the year ended December 31, 2020 and the periods from July 16, to December 31, 2019 (Successor) and January 1, 2019 to July 15, 2019 (Predecessor) is presented below (in thousands): Successor Company Predecessor Year Ended Period from Period from Balance at beginning of period $ 2,885 $ 5,735 $ — Adoption of ASC 606 — — 4,320 Costs amortized (1,670 ) (189 ) (824 ) Additional amounts deferred 7,684 3,074 2,239 Acquisition-related adjustment — (5,735 ) Balance at end of period $ 8,899 $ 2,885 $ 5,735 Classified as: Current 2,947 769 — Non-current 5,952 2,116 — Total deferred contract costs (deferred commissions) $ 8,899 $ 2,885 $ — Contract Liabilities A summary of the activity impacting deferred revenue balances during the year ended December 31, 2020 and the periods from July 16, 2019 to December 31, 2019 and January 1, 2019 to July 15, 2019, is presented below (in thousands): Successor Company Predecessor Year Ended Period from Period from Balance at beginning of period $ 46,125 $ 38,278 $ 32,187 Adoption of ASC 606 — — (729 ) Acquisition adjustment — (6,278 ) — Revenue recognized 1 (118,317 ) (40,045 ) (45,458 ) Additional amounts deferred 1 133,392 54,170 52,278 Balance at end of period $ 61,200 $ 46,125 $ 38,278 1 Amounts include total revenue deferred and recognized during each respective period. Remaining Performance Obligations ASC 606 introduced the concept of transaction price allocated to the remaining performance obligations of a contract, which is different than unbilled deferred revenue under ASC 605. Transaction price allocated to remaining performance obligations represents contracted revenue that has not yet been recognized, which includes unearned revenue and unbilled amounts that will be recognized as revenue in future periods. Transaction price allocated to remaining performance obligations is influenced The remaining performance obligations consisted of the following (in thousands): Successor Company December 31, December 31, Current (1) $ 114,284 $ 82,291 Noncurrent (1) 58,250 40,475 Total $ 172,534 $ 122,766 (1) The above table has been corrected for certain errors. Previously reported current, noncurrent and total amounts were $121,623, $51,368, and $172,991 respectively for 2020 and $90,237, $32,957, and $123,194 respectively for 2019.

Accounts Receivable

Accounts Receivable	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Accounts Receivable, after Allowance for Credit Loss, Current [Abstract]
Accounts Receivable	5. Accounts Receivable Accounts receivable consisted of the following: (in thousands) September 30, December 31, Accounts receivable $ 28,243 $ 33,635 Unbilled receivable 496 329 28,739 33,964 Less: allowance for doubtful accounts (853 ) (856 ) Accounts receivable, net $ 27,886 $ 33,108	5. Accounts Receivable Accounts receivable consisted of the following (in thousands): Successor Company December 31, December 31, Accounts receivable $ 33,635 $ 25,220 Unbilled receivable 329 251 $ 33,964 $ 25,471 Less: allowance for doubtful accounts (856 ) (450 ) Accounts receivable, net $ 33,108 $ 25,021

Property and Equipment

Property and Equipment	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Property and Equipment	6. Property and Equipment Property and equipment consisted of the following: (in thousands) September 30, December 31, Computers and software $ 4,455 $ 3,141 Furniture and equipment 1,580 1,109 Leasehold improvements 2,766 1,781 Construction — 128 8,801 6,159 Less: accumulated depreciation and amortization (4,104 ) (2,911 ) Property and equipment, net $ 4,697 $ 3,248 Depreciation and amortization expense associated with property and equipment was $1.2 million and $0.8 million for the nine months ended September 30, 2021 and 2020, respectively.	6. Property and Equipment Property and equipment consisted of the following (in thousands): Successor Company December 31, December 31, Computers and software $ 3,141 $ 2,042 Furniture and equipment 1,109 777 Leasehold improvements 1,781 1,188 Construction in process 128 310 $ 6,159 $ 4,317 Less: accumulated depreciation and amortization (2,911 ) (1,759 ) Property and equipment, net $ 3,248 $ 2,558 Depreciation and amortization expense was $1.2 million for the year ended December 31, 2020 (Successor), and $0.5 million and $0.4 million for the periods from July 16, 2019 through December 31, 2019 (Successor), and January 1, 2019 through July 15, 2019 (Predecessor), respectively.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	7. Goodwill and Intangible Assets The carrying amounts of goodwill and intangible assets, as of September 30, 2021 and December 31, 2020, consist of the following: September 30, 2021 (in thousands) Gross Accumulated Net Carrying Finite-lived intangible assets: Customer relationships $ 370,030 $ (84,159 ) $ 285,871 Developed technologies 51,100 (15,648 ) 35,452 Tradenames 35,500 (4,510 ) 30,990 Database 42,656 (28,246 ) 14,410 Total finite-lived intangible assets 499,286 (132,563 ) 366,723 Goodwill 1,261,444 — 1,261,444 Total goodwill and Intangible assets $ 1,760,730 $ (132,563 ) $ 1,628,167 December 31, 2020 (in thousands) Gross Accumulated Net Carrying Finite-lived intangible assets: Customer relationships $ 370,030 $ (58,097 ) $ 311,933 Developed technologies 51,100 (10,218 ) 40,882 Tradenames 35,500 (2,952 ) 32,548 Database 42,656 (17,782 ) 24,874 Total finite-lived intangible assets 499,286 (89,049 ) 410,237 Goodwill 1,261,444 — 1,261,444 Total goodwill and Intangible assets $ 1,760,730 $ (89,049 ) $ 1,671,681 Amortization expense associated with finite-lived intangible assets was $43.5 million for both the nine months ended September 30, 2021 and 2020, of which $15.9 million and $14.3 million was included in cost of revenue for the respective periods. There were no changes to the carrying amount of goodwill in the nine months ended September 30, 2021. The Company determined it had one reporting unit. There was no impairment of goodwill in the nine months ended September 30, 2021 or 2020.	7. Goodwill and Intangible Assets The carrying amounts of goodwill and intangible assets, as of December 31, 2020 and 2019, consist of the following (in thousands): December 31, 2020 (Successor) Gross Carrying Accumulated Net Carrying Finite-lived intangible assets: Customer relationships $ 370,030 $ (58,097 ) $ 311,933 Developed technologies 51,100 (10,218 ) 40,882 Tradenames 35,500 (2,952 ) 32,548 Data 42,656 (17,782 ) 24,874 Total finite-lived intangible assets 499,286 (89,049 ) 410,237 Goodwill 1,261,444 — 1,261,444 Total goodwill and Intangible assets $ 1,760,730 $ (89,049 ) $ 1,671,681 December 31, 2019 (Successor) Gross Carrying Accumulated Net Carrying Finite-lived intangible assets: Customer relationships $ 358,130 $ (21,075 ) $ 337,055 Developed technologies 48,500 (3,206 ) 45,294 Tradenames 34,100 (928 ) 33,172 Data 36,268 (5,408 ) 30,860 Total finite-lived intangible assets 476,998 (30,617 ) 446,381 Goodwill 1,233,173 — 1,233,173 Total goodwill and Intangible assets $ 1,710,171 $ (30,617 ) $ 1,679,554 Amortization expense associated with finite-lived intangible assets was $58.4 million for the year ended December 31, 2020 (Successor), of which $19.4 million was included in cost of revenue for the said period. Amortization expense associated with finite-lived intangible assets was $30.6 million and $2.0 million for the periods from July 16, 2019 through December 31, 2019 (Successor), and January 1, 2019 through July 15, 2019 (Predecessor), respectively. Estimated total intangible amortization expense during the next five years and thereafter is as follows (in thousands): 2021 $ 58,143 2022 53,653 2023 45,709 2024 42,485 2025 38,296 Thereafter 171,951 Total $ 410,237 The changes in the carrying amount of goodwill for the year ended December 31, 2020 (Successor) and the periods from July 16, 2019 to December 31, 2019 (Successor) and January 1, 2019 through July 15, 2019 (Predecessor) were as follows (in thousands): Balance at January 1, 2019 (Predecessor) $ 63,623 HIMSS acquisition (Note 3) 19,145 Balance at July 15, 2019 (Predecessor) 82,768 Definitive Holdco Acquisition (Note 3) $ 1,144,494 Balance at July 16, 2019 (Successor) $ 1,227,262 HSE acquisition (Note 3) 5,911 Balance at December 31, 2019 (Successor) 1,233,173 Monocl acquisition (Note 3) 28,271 Balance at December 31, 2020 (Successor) $ 1,261,444 The Company determined it had one reporting unit. The Company performed its annual impairment assessment in the fourth quarter of 2020 and 2019 and determined there was no impairment in 2020 or 2019.

Long-term debt

Long-term debt	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Debt Disclosure [Abstract]
Long-Term Debt	8. Long-Term Debt Long-term debt consisted of the following as of September 30, 2021 and December 31, 2020, respectively: September 30, 2021 (in thousands) Principal Unamortized debt Total debt, 2021 Term Loan $ 275,000 $ (2,737 ) $ 272,263 Less: current portion of long-term debt 6,875 Long-term debt $ 265,388 December 31, 2020 (in thousands) Principal Unamortized debt Total debt, 2019 Term Loan $ 444,375 $ (10,865 ) $ 433,510 Paid in kind interest on 2019 Term Loan 10,412 — 10,412 2019 Delayed Draw Term Loan 17,955 — 17,955 Total debt $ 472,742 $ (10,865 ) $ 461,877 Less: current portion of long-term debt 4,680 Long-term debt $ 457,197 On September 17, 2021, the Company totaling $474.6 million using the proceeds from the 2021 Term Loan, as described below, of $275.0 million and net proceeds of the IPO of $199.6 million , inclusive of accrued interest expense. rate for these loans under the 2019 Credit Agreement, as described below, was 6.25% as of the repayment date. The Company recognized a $9.9 million loss on the extinguishment of debt relating to the write off of unamortized debt issuance costs. 2021 Credit Agreement On September 17, 2021, Definitive Healthcare Holdings, LLC, a Delaware limited liability company (“DH Holdings”), an indirect subsidiary of Definitive Healthcare Corp., America The 2021 Term Loan is subject to annual amortization of principal, payable in equal quarterly installments on the last day of each fiscal quarter, commencing on December 31, 2021 (the “Initial Amortization Date”), equal to approximately 2.5% per annum of the principal amount of the term loans in the first year and second year after the Initial Amortization Date and approximately 5.0% per annum of the principal amount of the term loans in the third year, fourth year and fifth year after the Initial Amortization Date. A balloon payment of approximately $220.0 million will be due at the maturity of the 2021 Term Loan. There was $275.0 million outstanding on the 2021 Term Loan at September 30, 2021. DH Holdings is required to pay the lenders under the 2021 Credit Agreement an unused commitment fee of between 0.25% and 0.30% per annum on the undrawn commitments under the 2021 Revolving Line of Credit, depending on the total net leverage ratio, quarterly in arrears. The expense is included in interest expense in the statements of operations. There was no outstanding balance on the 2021 Revolving Line of Credit at September 30, 2021. For both the 2021 Term Loan and 2021 Revolving Line of Credit, DH Holdings may elect from several interest rate options based on the LIBO Rate or the Base Rate plus an applicable margin. The applicable margin will be based on the total leverage ratio beginning in the fiscal year ended December 31, 2022. As of September 30, 2021, the effective interest rate was 2.37%. In connection with the 2021 Credit Agreement, the Company capitalized financing costs totaling $3.5 million, $2.8 million for the 2021 Term Loan facility and $0.8 million for the 2021 Revolving Line of Credit. The financing costs associated with the 2021 Term Loan facility are recorded as a contra-debt balance in Term loan, net of current portion in the condensed consolidated balance sheets and are amortized over the remaining life of the loan using the effective interest method. The financing costs associated with the 2021 Revolving Line of Credit are recorded in Other assets in the condensed consolidated balance sheet are amortized over the life of the arrangement. 2019 Credit Agreement On July 16, 2019, DH Holdings entered into a credit agreement (the “2019 Credit Agreement”) by and among DH Holdings, the lenders party thereto and Owl Rock Capital Corporation, as administrative agent. Under the 2019 Credit Agreement, a $450.0 million term loan facility (the “2019 Term Loan”), a $100.0 million delayed draw term loan facility (the “2019 Delayed Draw Term Loan”) and a $25.0 million revolving line of credit (the “2019 Revolving Line of Credit”) were made available to DH Holdings. The 2019 Credit Agreement included customary affirmative, negative and financial covenants. All facilities under the 2019 Credit Agreement were guaranteed, by DH Holdings’s wholly-owned domestic restricted subsidiary, Definitive Healthcare LLC, a Massachusetts limited liability company and AIDH Buyer, LLC, a Delaware limited liability company and the direct parent company of DH Holdings, and were secured by a lien on substantially all of the assets of DH Holdings and the guarantors, including a pledge of the equity of DH Holdings, in each case, subject to customary exceptions. The 2019 Term Loan had a maturity date of July 16, 2026 and was issued with an original issue discount of $11.3 million and amortized to interest expense over the term of the agreement using the effective interest method. Interest on a portion of the loan ($100.0 million of the $450.0 million principal amount) was treated as paid in kind and added to the principal balance to be paid off at maturity. DH Holdings could elect from several interest rate options based on the Eurodollar The 2019 Delayed Draw Term Loan had a maturity of July 16, 2026. The 2019 Delayed Draw Term Loan was issued with an original issue discount of $1.3 million. DH Holdings could draw down funds under the 2019 Delayed Draw Term Loan until July 16, 2021. As of December 31, 2020, DH Holdings drew $18.0 million on the 2019 Delayed Draw Term Loan, in connection with the Monocl acquisition. DH Holdings could elect from several interest rate options based on the Eurodollar The 2019 Revolving Line of Credit had a maturity of July 16, 2024. DH Holdings could elect from several interest rate options based on the Eurodollar Rate or the Base Rate plus an applicable margin. During 2020, $ million was drawn on the 2019 Revolving Line of Credit and subsequently paid back in 2020. There was outstanding balance on the 2019 Revolving Line of Credit at December 31, 2020. draws on the 2019 Revolving Line of Credit were made in 2021 and the 2019 Credit Agreement was terminated on September 17, 2021 . In connection with the 2019 Credit Agreement, the Company originally capitalized financing costs totaling $14.1 million, $13.4 million for the 2019 Term Loan and $0.7 million for the 2019 Revolving Line of Credit. In October 2020, the Company capitalized an additional $0.2 million in financing costs associated with the 2019 Delayed Draw Term Loan borrowing. These financing costs were recorded as deferred financing costs in the condensed consolidated balance sheets and amortized over the remaining lives of the respective borrowing using the effective interest method. The Company expensed capitalized financing costs for the 2019 Credit Agreement through interest expense of $1.5 million for the nine months ended September 30, 2021 and 2020, respectively. At December 31, 2020, the unamortized financing costs for the 2019 Revolving Line of Credit of $0.5 million was classified in other assets in the consolidated balance sheet.	8. Long-Term Debt Long-term debt consisted of the following as of December 31, 2020 and 2019, respectively (in thousands): December 31, 2020 (Successor) Principal Unamortized debt Total debt, net 2019 Term Note $ 444,375 $ (10,865 ) $ 433,510 Paid in kind interest on 2019 Term Note 10,412 10,412 2019 Delayed Draw Term Note 17,955 17,955 Total debt $ 472,742 $ (10,865 ) 461,877 Less: current portion of long-term debt 4,680 Long-term debt $ 457,197 December 31, 2019 (Successor) Principal Unamortized debt Total debt, net 2019 Term Note $ 448,875 $ (12,567 ) $ 436,308 Paid in kind interest on 2019 Term Note 3,041 3,041 Total debt $ 451,916 $ (12,567 ) 439,349 Less: current portion of long-term debt 4,500 Long-term debt $ 434,849 Term Loan Payable On July 16, 2019, the Company entered into a term loan facility, delayed draw term loan, and revolving line of credit (collectively, “2019 Loan Agreement”). The term loan facility (“2019 Term Note”) is for $450.0 million, which has a maturity date of July 16, 2026. The 2019 Term Note was issued with an original issue discount of $11.3 million. This discount is amortized to interest expense over the term of the agreement using the effective interest method. Interest on a portion of the loan ($100.0 million of the $450.0 million principal amount) is treated as paid in kind and added to the principal balance to be paid off at maturity. The Company can elect from several interest rate options based on the Eurodollar Rate or the Base Rate plus an applicable margin (As of December 31, 2020, the interest rate was 6.5% on both the $350.0 million loan and the $100.0 million paid in kind loan. At December 31, 2019, the interest rate was 8.404% on the $100.0 million paid in kind loan and 7.404% on the $350.0 million loan). Quarterly principal payments of $1.1 million began in December 2019 and are required through the note’s maturity, at which time a balloon payment of $419.6 million, excluding the paid in kind portion, will be due. The paid in kind interest is payable on the maturity date. The note is subject to certain financial covenants and is collateralized by first security interests on the Company’s assets. The loan is subject to excess cash flow payments annually beginning in the fiscal year ended December 31, 2020 based on the total leverage ratio. There was $454.8 million and $451.9 million outstanding on the 2019 Term Note at December 31, 2020 and 2019, respectively, including $10.4 million and $3.0 million of paid in kind interest, respectively. Delayed Draw Term Loan Payable On July 16, 2019, as part of the 2019 Loan Agreement, the Company entered into a delayed draw term loan (“2019 Delayed Draw Term Note”) of $100.0 million which has a maturity of July 16, 2026. The 2019 Delayed Draw Term Note was issued with an original issue discount of $1.3 million. The Company may draw down funds under the 2019 Delayed Draw Term Note until July 16, 2021. As of December 31, 2020, the Company drew $18.0 million on the 2019 Delayed Draw Term Note, in connection with the Monocl acquisition. The Company can elect from several interest rate options based on the Eurodollar Rate or the Base Rate plus an applicable margin. Quarterly in arrears through July 16, 2021, the Company is required to pay the bank a fee equal to 1% per annum of the amount of the 2019 Delayed Draw Term Note unused capacity. Quarterly principal payments begin in September 2021 in quarterly installments equal to 0.25% of the aggregate amount outstanding on the 2019 Delayed Draw Term Note, and are required through the note’s maturity, at which time a payment of the entire outstanding principal balance will be due. The note is subject to certain financial covenants and is collateralized by first security interests on the Company’s assets. The outstanding balance on the 2019 Delayed Draw Term Note was $18.0 million at December 31, 2020. There was no outstanding balance at December 31, 2019. Revolving Line of Credit On July 16, 2019, as part of the 2019 Loan Agreement, the Company entered into a revolving line of credit (“2019 Revolving Line of Credit”) of $25.0 million which has a maturity of July 16, 2024. The Company can elect from several interest rate options based on the Eurodollar Rate or the Base Rate plus an applicable margin. Quarterly in arrears, the Company is required to pay the bank a fee equal to 0.5% of the amount of the 2019 Revolving Line of Credit’s unused capacity. The expense is included in interest expense in the statement of income (loss). The 2019 Revolving Line of Credit is subject to certain financial covenants. During 2020, $25.0 million was drawn on the on the Revolving Line of Credit and subsequently paid back. There was no outstanding balance on the 2019 Revolving Line of Credit at December 31, 2020 or 2019. Line of Credit On January 8, 2019, in conjunction with the acquisition of HIMSS, the Company entered into a revolving line of credit (“2019 Revolver”) of $15.0 million with a maturity date of January 8, 2021. Loans under the 2019 Revolver were subject to several interest rate options based on the Eurodollar Rate or the Base Rate plus an applicable margin and were collateralized by a first security interest in the Company’s assets. Quarterly in arrears, the Company was required to pay the bank a fee equal to 0.3% of the amount of the 2019 Revolver’s unused capacity. The expense was included in interest expense on the consolidated statement of operations. The 2019 Revolver was subject to certain financial covenants. The Company drew down $13.0 million to fund the acquisition of HIMSS. During 2019, the 2019 Revolver was paid in full with cash on hand and terminated. Financing Costs Capitalized financing costs represent costs incurred by the Company to obtain financing and are amortized over the term of the applicable loan using the effective interest method. During the year ended December 31, 2019, the Company incurred $1.6 million and $12.5 million of financing costs and original issue discounts, respectively. The amount is amortized to interest expense through the maturity dates of the underlying debt. The original issue discount is treated as a debt discount. The Company expensed capitalized financing costs and the debt discount through interest expense of $0.9 million during the period from July 16, 2019 through December 31, 2019 (Successor). No capitalized financing costs were expensed during the period from January 1, 2019 through July 15, 2019. As of December 31, 2020 and 2019, the unamortized financing costs for the 2019 Revolving Line of Credit of $0.5 million and $0.6 million, respectively, was classified in other assets in the consolidated balance sheet. Future principal payments as of December 31, 2020 are as follows (in thousands): 2021 $ 4,680 2022 4,680 2023 4,680 2024 4,680 2025 4,680 Thereafter 449,342 $ 472,742

Fair Value Measurements

Fair Value Measurements	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	9. Fair Value Measurements ASC 820, Fair Value Measurements and Disclosures The Company’s financial assets and liabilities subject to the three-level fair value hierarchy consist principally of cash and equivalents, accounts receivable, accounts payable, long-term and short-term debt and contingent consideration payable. The estimated fair value of cash and equivalents, accounts receivable and accounts payable approximates their carrying value due to due to their short maturities (less than 12 months). The Company’s short- and long-term debt are recorded at their carrying values in the consolidated balance sheets, which may differ from their respective fair values. The carrying values and estimated fair values of the Company’s short- and long-term debt approximate their carrying values as of December 31, 2020, and 2019, based on interest rates currently available to the Company for similar borrowings. The contingent consideration, which resulted from the earn-outs associated with the Monocl acquisition, is measured at fair value on a recurring basis. The fair value was estimated using a variation of the income approach, known as the real options method, where ARR was simulated in a risk-neutral framework using Geometric Brownian Motion, a well-accepted model of stock price behavior that is used in option pricing models such as the Black-Scholes option pricing model. The risk-neutral expected (probability-weighted) earnout payments were then calculated based on simulation results. An increase to a probability of achievement would result in a higher fair value measurement. At September 30, 2021 and December 31, 2020, the fair value of the contingent consideration was estimated at $6.9 million and $5.2 million, respectively. The current portion of the earn-out non-current Earn-out (in thousands) Fair Value Valuation Technique Unobservable Inputs Discount Rate Earn-out $ 6,905 Income Approach (Real Option Method) Discount rate 2.38 % The table below presents a reconciliation of earnout liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3): (in thousands) September 30, December 31, Balance at beginning of period $ 5,236 $ — Additions — 2,600 Net change in fair value and other adjustments 3,169 2,636 Payments (1,500 ) — Balance at end of period $ 6,905 $ 5,236 Adjustments to the earn-out the potential to make a maximum of $10.0 million and a minimum of $0.0 million (undiscounted) in earn-out earn-out Certain assets and liabilities, including property, plant and equipment, goodwill and other intangible assets, are measured at fair value on a non-recurring Summary of Significant Accounting Policies	9. Fair Value Measurements AC 820, Fair Value Measurements and Disclosures (“ASC 820”), defines fair value as the price that would be received for an asset, or paid to transfer a liability, in an orderly transaction between market participants on the measurement date, and establishes a three-level fair value hierarchy that prioritizes the inputs used to measure fair value. The Company’s financial assets and liabilities subject to the three-level fair value hierarchy consist principally of cash and equivalents, accounts receivable, accounts payable, long-term and short-term debt and contingent consideration payable. The estimated fair value of cash and equivalents, accounts receivable and accounts payable approximates their carrying value due to due to their short maturities (less than 12 months). The Company’s short- and long-term debt are recorded at their carrying values in the consolidated balance sheets, which may differ from their respective fair values. The carrying values and estimated fair values of the Company’s short- and long-term debt approximate their carrying values as of December 31, 2020, and 2019, based on interest rates currently available to the Company for similar borrowings. The contingent consideration, which resulted from the earn-outs associated with the Monocl acquisition, is measured at fair value on a recurring basis. The current portion of the earn-out non-current Earn-out achievement would result in a higher fair value measurement. The fair value of the contingent consideration was $5.2 million as of December 31, 2020, with $1.5 million current and $3.7 million non-current. earn-out earn-out earn-out The table below presents a reconciliation of earnout liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) (in thousands): Successor Company Predecessor Company Year ended Period from Period from Balance at beginning of period $ — $ — $ — Additions 2,600 — — Net change in fair value and other adjustments 2,636 — — Payments — — — Balance at end of period $ 5,236 $ — $ — The valuation techniques and significant unobservable inputs used in recurring Level 3 fair value measurements were as follows as of December 31, 2020: Fair Value Valuation Technique Unobservable Inputs Discount Rate Earn-out $ 5,236 Income Approach (Real Option Method) Discount rate 6.5 % Certain assets and liabilities, including property, plant and equipment, goodwill and other intangible assets, are measured at fair value on a non-recurring Summary of Significant Accounting Policies Goodwill and Intangible Assets

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Payables and Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	10. Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consisted of the following: (in thousands) September 30, 2021 December 31, 2020 Payroll and payroll-related $ 7,246 $ 7,792 Accrued interest 233 5,365 Contingent consideration, current 6,905 1,500 Sales taxes 1,146 649 Deferred rent 112 583 Other 3,654 1,432 Accrued expenses and other current liabilities $ 19,296 $ 17,321	10. Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consisted of the following (in thousands): Successor Company December 31, 2020 December 31, 2019 Payroll and payroll-related $ 7,792 $ 3,879 Accrued interest 5,365 4,215 Contingent consideration, current 1,500 — Sales taxes 649 1,916 Deferred rent 583 17 Other 1,432 321 Accrued expenses and other current liabilities $ 17,321 $ 10,348

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	11. Commitments and Contingencies The Company leases office facili t Total rent expense for the nine months ended September 30, 2021 was $2.1 million, respectively, and rent expense for the nine months ended September 30, 2020 was $1.4 million, respectively. Rent expense was classified in selling, general, and administrative expense in the condensed consolidated statements of operations for all periods presented.	11. Commitments and Contingencies The Company leases office facilities in Massachusetts, Vermont and Sweden, the terms of which expire at various times through the year 2030. Beginning in 2017, the Predecessor subleased one of its Massachusetts offices. The sublease term expired in August 2019 and the Company recorded sublease rental income of $0.1 million for the year ended December 31, 2019. The income was recorded as an offset to rent expense in the consolidated statements of income (loss). There was no income from any sublease agreements recorded in 2020. Total rent expense was $1.8 million for the year ended December 31, 2020 (Successor) and $0.6 million and $0.5 million for the periods from July 16, 2019 through December 31, 2019 (Successor) and from January 1, 2019 through July 15, 2019 (Predecessor), respectively, and was classified in selling, general, and administrative expense in the consolidated statements of income (loss). The Company signed a new office lease agreement in 2019 which commenced in 2020 and will continue through 2027. The table below is inclusive of the new lease. Minimum future rental payments are expected to be as follows for each of the years ending December 31 (in thousands): 2021 $ 3,035 2022 2,673 2023 2,043 2024 2,338 2025 2,193 Thereafter 4,790 $ 17,072 The Company also enters into other purchase obligations in the normal course of doing business. The estimated annual minimum purchase commitments under those agreements were as follows for each of the years ending December 31 (in thousands): 2021 $ 5,396 2022 5,257 2023 5,098 2024 3,925 2025 2,370 Thereafter — $ 22,046

Members' capital

Members' capital	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Members' capital	12. Members’ capital Successor As described in Note 1. Overview Combinations Upon formation of the Company, two classes of units were established: Class A Units (“Class A Units”) and Class B Units (“Class B Units”), collectively the Units. On July 16, 2019, 100% of the issued and outstanding Legacy Common Units of Definitive Holdco were acquired by AIDH Buyer, an affiliated legal entity of Advent and a wholly owned subsidiary of the Company. As part of the Definitive Holdco Acquisition, the Company issued 127,725,743 Class A Units at $10 per unit for total contributed capital of $1,267.3 million. Additionally, the outstanding units of the Legacy Class B Series B, Series C, Series D, and Series E were sold to AIDH Buyer and the holders received a combination of cash and equity in the Company. In conjunction with the acquisition of Definitive Holdco by the Company in July 2019, the Company paid $6.9 million to the selling shareholders in July 2020 which had been recorded as a members’ distribution payable on the balance sheet at December 31, 2019 (see Note 3. Business Combinations In 2019, the Company contributed $4.0 million worth of its Class A Units to partially fund the acquisition of HSE that occurred in December 2019 (see Note 3. Business Combinations In 2020, the Company contributed $25.4 million worth of its Class A units to partially fund the acquisition of Monocl that occurred in October 2020 (see Note 3. Business Combinations There was 130,245,990 and 127,125,435 issued and outstanding Class A units as of December 31, 2020 and December 31, 2019, respectively. Predecessor Upon formation of the Predecessor Company, two classes of common units were established; Class A Common Units (“Legacy Class A Units”) and Class B Common Units (“Legacy Class B Units”), collectively the Legacy Common Units. In December 2016, the Predecessor amended and restated the Limited Liability Company Agreement of Definitive Holdco, resulting in the formation of DHC Class B Holdings, LLC (“DHCB”). Per the terms of Limited Liability Company Agreement of DHC Class B Holdings, LLC (the “DHCB Holdings Agreement”), DHCB’s units represented an indirect interest in Class B Units of the Company. Upon formation of DHCB all previously issued Class B Units were exchanged for DHCB Series B Units, and the previously authorized Class B Units were transferred to DHCB. The DHCB Holdings Agreement allowed for the creation a series of units (the “Incentive Equity Pool”), upon approval by the Management Board, up to the cumulative authorized amount of 407,750. The rights and obligations of the holders of the Common Units were governed by the Amended and Restated Limited Liability Company Agreement of Definitive Healthcare Holdings, LLC, (the “Agreement”). The Agreement provided for the limitation of the holders liability to be that of their respective capital contributions as defined in the Agreement. Per the Agreement, all unit holders were entitled to receive the following distributions from the Company: tax distributions, distributions on liquidation or sale of the Company, or distributions prior to liquidation or sale of the Company. Per the terms of the Agreement tax distributions should be made for the amount of income allocated to the Member multiplied by the applicable federal income tax rate. As of December 31, 2018, 7,750,000 Legacy Class A Units were authorized, issued, and outstanding and 407,750 Legacy Class B Units (Series A though E) were authorized to be issued to employees and consultants as incentive units, of which 88,716 units were outstanding As of July 15, 2019, there were 7,750,000 and 268,853 of issued and outstanding Legacy Class A and Legacy Class B Units, respectively. On July 16, 2019, 100% of the Legacy Class A Units were acquired by AIDH Buyer, in conjunction with the sale of the Legacy Class A Units, the outstanding units of Series B, C, D, and E were sold and the holders received a combination of cash and equity in the Company.

Equity-based Compensation

Equity-based Compensation	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Equity-based Compensation	13. Equity-Based Compensation Equity-based compensation expense is allocated to all departments in the accompanying condensed consolidated statements of operations based on the recipients of the compensation . A summary of the expense by line item in the consolidated statements of operations for the nine months ended September 30, 2021 and 2020, respectively, is provided in the following table. Nine Months Ended (in thousands) 2021 2020 Cost of revenue $ 79 $ 46 Sales and marketing 567 380 Product development 341 267 General and administrative 3,351 637 Total compensation expense $ 4,338 $ 1,330 2021 Equity Incentive Plan As of September 15, 2021, in connection with its IPO, the Company adopted the Definitive Healthcare Corp. 2021 Equity Incentive Plan (the “2021 Plan”). The types of grants available under the 2021 Plan include stock options (both incentive and non-qualified), The aggregate number of shares of Class A Common Stock available for grant under the 2021 Plan was 8,989,039 shares at September 30, 2021. As of September 30, 2021, 1,464,681 RSUs have been granted under the 2021 Plan. The outstanding RSUs have time-based and/or performance-based vesting criteria. Outstanding time-based RSUs generally vest partially on the one year anniversary of each grant and quarterly over the subsequent two- The following table summarizes the Company’s unvested time-based and performance-based RSU activity for the nine months ended September 30, 2021. Time-Based Performance-Based Restricted Stock Units Weighted Average Grant Date Fair Value Restricted Stock Units Weighted Average Grant Date Fair Value Unvested at beginning of period — $ — — $ — Granted 1,300,328 $ 27.00 164,353 $ 27.00 Vested — $ — — $ — Forfeited (2,656 ) $ 27.00 — $ — Unvested at end of period 1,297,672 $ 27.00 164,353 $ 27.00 The Company recognized $0.4 million in stock-based compensation expense associated with RSUs granted in 2021. Total unrecognized expense was estimated to be $39.1 million for both time-based vesting and performance-based vesting awards at September 30, 2021, to be recognized over a weighted-average period of approximately 4.0 years. 2019 Equity Incentive Plan In July 2019, the Company and its Board of Members approved the 2019 Equity Incentive Plan (“the 2019 Plan”) under which the Parent Company had reserved approximately 8,088,877 Class B Units (the “2019 Incentive Equity Pool”). The 2019 Incentive Equity Pool was utilized for the issuance of units to employees, consultants, directors, managers, or others providing services to the Company pursuant to Board of Members approval. These interests were considered profit interests, which, in general, entitle the holder of the unit to a pro rata share of the increase in value of the unit over the base value determined at the award date and were subject to such vesting and other restrictions as the Board of Members deemed appropriate. Any units forfeited or repurchased were available for future grants under the 2019 Incentive Equity Pool. The units had time-based and/or performance-based vesting criteria. Generally, the time-based units vested in equal annual installments over a four-year period on the anniversary date of the vest date. The performance-based units vested based on the achievement of specified returns on investments upon a change of control or qualifying event, as defined in the agreement. In connection with the IPO, performance-based forfeiture conditions for unvested units were waived through a modification of the awards and, after the IPO, all such unvested awards became subjected to time-vesting over three years from the IPO Date. As a result of the modification of the terms of such performance-vesting awards, we recorded compensation expense based on the fair value of the units that otherwise would have been forfeited, using the IPO price of $27.00 per share. The total compensation expense related to modification was $9.0 million, which will be recognized over the respective remaining service periods. The Company recorded $0.2 million in stock-based compensation expense associated with these performance-vesting units in the third quarter of 2021. In connection with the retirement of an executive officer, the Company accelerated the vesting of 24,049 unvested time-vesting Class B units and 48,099 of his unvested performance-vesting Class B units. The Company recorded incremental compensation expense of approximately $1.9 million during the third quarter 2021. Upon separation, the remaining 72,149 in Effective September 15, 2021, the Company will no longer grant any awards under the 2019 Plan, though previously granted awards under the 2019 Plan remain outstanding and governed by the 2019 Plan, except for the modifications discussed above. For awards granted in the 2019 Plan, the Company assessed the fair value of the awards as of the grant date. The fair value of the units was estimated using a two-step September 15, 2021 December 31, 2020 Expected option term 0.30 — 5.5 years Risk-free rate of return 0.01% — 1.73% Applied volatility 30% 35% In connection with the Reorganization Transactions and the IPO, unvested Class B Units held directly by employees of the Company or indirectly through Definitive OpCo, were exchanged for unvested Definitive OpCo units based on their respective participation thresholds and the IPO price of $27.00 per share. The time-based units issued upon the exchange remain subject to the same service vesting requirements as the original Class B Units. The pre-IPO performance-based units were exchanged for time-based units and will vest over a three-year period beginning on the date of the IPO. The following table summarizes the Company’s unvested time-based and performance-based unit activity from January 1, 2021 through September 30, 2021. Time-Based Performance-Based Non-Vested Weighted Non-Vested Weighted Non-vested 1,404,720 $ 3.65 1,840,423 $ 2.35 Granted 1,477,323 1.41 1,177,308 0.41 Vested (437,731 ) 3.64 — — Forfeited (13,770 ) 3.65 (18,361 ) 2.35 Non-vested 2,430,542 $ 2.29 2,999,370 $ 1.59 Effect of Reorganization Transactions and IPO (1,165,679 ) 2.08 (1,318,171 ) 1.39 Performance-based units exchanged for time-based units 1,681,199 1.74 (1,681,199 ) 1.74 Vested (74,049 ) 2.75 — — Forfeited (72,149 ) 2.78 — — Non-vested 2,799,864 $ 2.02 — $ — In connection with the Reorganization Transactions and the IPO, 912,651 vested Class B Units held directly by employees of the Company or indirectly through Definitive OpCo were exchanged into 578,217 vested Definitive OpCo units based on their respective participation thresholds and the IPO price of $27.00 The Company recorded $1.5 million in stock-based compensation expense associated with time-based units in the nine months ended September 30, 2021 .	13. Equity-based Compensation 2019 Incentive Equity Plan In July 2019, the Company and its Board of Members approved the 2019 Equity Incentive Plan under which the Parent Company has reserved approximately 8,088,877 Class B Units (the “2019 Incentive Equity Pool”). The 2019 Incentive Equity Pool is to be utilized for the issuance of units to employees, consultants, directors, managers, or other providing services to the Company pursuant to Board of Members approval. These interests are considered profit interests, which, in general, entitle the holder of the unit to a pro rata share of the increase in value of the unit over the base value determined at the award date and may be subject to such vesting and other restrictions as the Board of Members may deem appropriate. Any units forfeited or repurchased shall be available for future grants under the 2019 Incentive Equity Pool. The units have time-based and performance-based vesting criteria. Generally, the time-based units vest in equal annual installments over a four-year period on the anniversary date of the vest date. The performance-based units vest based on the achievement of specified returns on investments upon a change of control, as defined in the agreement. Upon initial public offering unvested performance-based units would convert to restricted shares subject to 3 year vesting. The Company assesses the fair value of the awards as of the grant date. The fair value of the units was estimated using a two-step Successor Company Year ended Period from Expected option term 5.5 years 5.5 years Risk-free rate of return 1.73 % 1.73 % Applied volatility 35 % 35 % The expected option term represents management’s estimate of time to an exit event. The risk-free rate of return is based upon government securities with durations approximately equal to the option term. Applied volatility is based on the average volatility of the guideline companies. The following table summarizes the Company’s unvested time-based and performance-based unit activity under the 2019 plan for the year ended December 31, 2020 (Successor) and the periods from July 16, 2019 and December 31, 2019 (Successor) and January 1, 2019 to July 15, 2019 (Predecessor): Time-based Performance-based 2019 Plan Non-Vested Weighted Non-Vested Weighted Non-vested — $ — — $ — Granted — — — — Vested — — — — Non-vested — $ — — $ — Granted 1,899,682 3.65 1,899,682 2.35 Vested — — — — Forfeited — — — — Non-vested 1,899,682 $ 3.65 1,899,682 $ 2.35 Granted 97,611 3.65 97,611 2.35 Vested (474,920 ) 3.65 — — Forfeited (117,653 ) 3.65 (156,870 ) 2.35 Non-vested 1,404,720 $ 3.65 1,840,423 $ 2.35 During the year ended December 31, 2020 (Successor) and the period from July 16, 2019 to December 31, 2019 (Successor), 195,222 and 3,799,364 units, respectively, were granted under the plan. 2015 Incentive Equity Plan On July 16, 2019, in conjunction with the purchase of the issued and outstanding Common Units of the Definitive Holdco by AIDH Buyer, LLC, the outstanding units of Series B, Series C, Series D, and Series E were sold to AIDH Buyer, LLC and the holders received a combination of cash and equity in AIDH TopCo, LLC, and the 2015 Equity Incentive Plan was terminated. The 2015 Equity Incentive Plan under which the Company has reserved 407,750 Class B Units (the “2015 Incentive Equity Pool”) was approved in February 2015 by the Predecessor and Board of Managers. In December 2016, in connection with the amended and restated Limited Liability Company Agreement entered into, the 2015 Incentive Equity Pool was transferred to DHCB. The 2015 Incentive Equity Pool was utilized for the issuance of units to employees, consultants, directors, managers, or others providing service to the Company pursuant Board of Managers approval. Units granted out of the 2015 Incentive Equity Pool are designated series based on the period of grant, and prior to July 16, 2019, the outstanding units consisted of Series B, Series C, Series D, and Series E. These interests were considered profits interests, which in general, entitled the holder of the unit to a pro rata share of the increase in value of the unit over the base value determined at the award date and may be subject to such vesting and other restrictions as the Board of Managers may deem appropriate. Any units forfeited or repurchased were available for future grants under the 2015 Incentive Equity Pool. The following table summarizes the 2015 Plan activity for the periods from January 1, 2019 through July 15, 2019 (Predecessor), and July 16, 2019 through December 31, 2019 (Successor). 2015 Plan Non-Vested Weighted Non-vested 131,545 $ 9.00 Granted 48,592 98.75 Vested (180,137 ) 33.21 Forfeited — — Non-vested — $ — Granted — — Vested — — Forfeited — — Non-vested — $ — As of December 31, 2018 (Predecessor), the Company had authorized and issued, subject to vesting, 1 share of Class B Series A units, 73,418 shares of Class B Series B units, 57,105 shares of Class B Series C units, and 89,737 shares of Class B Series D units. During the year ended December 31, 2019, the Company authorized and issued 48,592 shares of Class B Series E units. On July 16, 2019, all shares of Series A, Series B, Series C, Series D, and Series E units vested upon the qualifying event and were cancelled. The Plan was also terminated on July 16, 2019. The Company recorded total unit-based compensation of $1.7 million for the year ended December 31, 2020 (Successor) and $0.7 million and $5.8 million for the periods from July 16, 2019 through December 31, 2019 (Successor) and from January 1, 2019 through July 15, 2019 (Predecessor), respectively, as follows in the table below (in thousands): Successor Company Predecessor Year ended Period From Period From Time-based: 2015 plan $ — $ — $ 5,807 2019 plan 1,747 744 — Total time-based 1,747 744 5,807 Performance based: 2015 plan — — — 2019 plan — — — Total performance-based — — — Total compensation expense $ 1,747 $ 744 $ 5,807 Equity-based compensation expense is allocated to all departments in the accompanying consolidated statements of income (loss) based on the recipients of the compensation. A summary of the expense by line item in the consolidated statements of income (loss) for the year ended December 31, 2020 (Successor) and the periods from July 16, 2019 to December 31, 2019 (Successor), and from January 1, 2019 to July 15, 2019 (Predecessor) is provided in the following table (in thousands). Successor Company Predecessor Year ended Period From Period From Cost of revenue $ 62 $ 28 $ 256 Sales and Marketing 473 213 4,252 Product Development 356 126 665 General and administrative 856 377 634 Total compensation expense $ 1,747 $ 744 $ 5,807 The Company does not consider the vesting of the performance-based units to be probable and has not recorded any associated compensation expense. Accordingly, the Company had $4.3 million of unrecognized unit-based compensation expense for the performance-based units as of December 31, 2020. As of December 31, 2020, the Company had $4.4 million of unrecognized unit-based compensation for time-based units, expected to be recognized over a weighted average remaining requisite period of 2.6 years.

Retirement Plan

Retirement Plan	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Retirement Benefits [Abstract]
Retirement Plan	14. Retirement Plan The Company has a 401(k) plan covering all employees who have met certain eligibility requirements. The Company incurred $1.7 million in employer matching contributions during the nin e .	14. Retirement Plan The Company has a 401(k) plan covering all employees who have met certain eligibility requirements. The Company made matching contributions in accordance with the plan documents. The Company incurred $1.6 million in employer matching contributions during the year ended December 31, 2020 and $0.5 million and $0.6 million during the periods from July 16, 2019 to December 31, 2019 (Successor), and from January 1, 2019 to July 15, 2019 (Predecessor), respectively.

Stockholders' Equity and Member

Stockholders' Equity and Members' Deficit	May 24, 2021	Sep. 30, 2021
Stockholders' Equity Note [Abstract]
Stockholders' Equity and Members' Deficit	3. Stockholder’s Equity The Corporation is authorized to issue 100 shares of Common Stock, par value $0.01 per share. In exchange for $100, the Corporation has issued 1 share of common stock, which is held by Advent International GPE IX Limited Partnership as of May 24, 2021.	12. Stockholders’ Equity and Members’ Equity The Company has Class A Common Stock, Class B Common Stock and Preferred Stock. Holders of outstanding shares of Class A Common Stock and Class B Common Stock will vote as a single class on all matters on which stockholders are entitled to vote generally, except as otherwise required by law. Class B Common Stock issued to holders of Definitive OpCo Units that are unvested shall have no vote per share until such time as such Units have vested . Class A Common Stockholders are entitled to receive dividends, if declared by our board of directors out of legally available funds. Upon our liquidation, dissolution or winding up and after payment in full of all amounts required to be paid to creditors and to the holders of Preferred Stock having liquidation preferences, if any, the holders of shares of our Class A Common Stock will be entitled to receive pro rata our remaining assets available for distribution. Class B Common Stockholders are not entitled to economic interests in Definitive Healthcare Corp. and do not have any right to receive dividends or to receive a distribution upon a liquidation or winding up of Definitive Healthcare Corp. Shares of Preferred Stock have not been issued at September 30, 2021. The board of directors may authorize one or more series of Preferred Stock (including convertible Preferred Stock) and will determine, with respect to any series of Preferred Stock, the voting rights, preferences, participation, or other special rights and limitations. Under the Amended Definitive OpCo LLC Agreement, the holders of LLC Units have the right to require Definitive OpCo to exchange all or a portion of their LLC Units for newly issued shares of Class A Common Stock, which may consist of unregistered shares, on a one-for-one one-for-one As described in Note 1. Description of Business The table below provides a summary of the number of Class A and Class B units authorized, issued and outstanding as of December 31, 2020, respectively. December 31, 2020 Class A units: Authorized, issued and outstanding Class A units 130,245,990 Class B units: Authorized Class B units 8,088,877 Issued Class B units 3,720,063 Outstanding Class B units (Vested Class B units) 474,920 During 2021, the Company issued 363,516 new Class A units worth $5.8 million, consisting of a capital contribution of $5.5 million and equity-based compensation expense of $0.3 million. Refer to Note 13. Equity-Based Compensation

Income Taxes

Income Taxes	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	15. Income Taxes As described in Note 1. Business Organization Stockholders’ Equity and Members’ Equity As of September 30, 2021, management performed an assessment of the recoverability of deferred tax assets. Management determined, based on the accounting standards applicable to such assessment, that sufficient negative evidence to conclude it was more likely than not that its deferred tax assets would not be realized and has recorded a valuation allowance against substantially all of its deferred tax assets. In the event that management determines the Company would be able to realize its deferred tax assets in the future in excess of their net recorded amount, an adjustment to the valuation allowance would be made which would reduce the provision for income taxes. As of September 30, 2021 the Company has a net deferred tax liability of $ 71.3 The Company recognizes uncertain income tax positions when it is more-likely-than-not nine . In connection with the IPO, the Company entered into a Tax Receivable Agreement (“TRA”) and recorded a liability under the TRA of million as of September 30, 2021 through equity as part of the Reorganization Transactions. Under the TRA, the Company generally will be required to pay certain of our pre-IPO owners	15. Income Taxes The components of the income tax provision are as follows (in thousands): Successor Company Predecessor Year ended Period from Period from Current tax provision: Federal $ 10 $ — $ — State 1 — — Foreign — — — Total current tax provision $ 11 $ — $ — Deferred tax provision: Federal $ 58 $ — $ — State (7 ) — 49 Foreign — — — Total deferred tax provision 51 — 49 Total provision $ 62 $ — $ 49 Deferred taxes are recognized for temporary differences between the basis of assets and liabilities for financial statement and income tax purposes. The significant components of the deferred tax assets are comprised of the following (in thousands): Successor Company December 31, 2020 December 31, 2019 Deferred tax assets: Foreign, U.S. and state net operating loss carryforwards $ 1,517 $ 212 Accrued Expenses 12 — Unrealized foreign exchange losses 62 — Subtotal 1,591 212 Less valuation allowance (1,430 ) — Total deferred tax assets 161 212 Net deferred tax assets $ 161 $ 212 A reconciliation of income tax expense computed at the statutory federal income tax rate to income taxes as reflected in the financial statements is as follows: Successor Company Predecessor Year ended Period from Period from Federal income tax expense at statutory rate 21.00 % 21.00 % 0.00 % State income tax, net of federal benefit (0.14 ) 0.04 0.00 Permanent differences (0.98 ) (2.73 ) 0.00 Research and development credit 0.00 0.00 0.00 Foreign rate differential (0.01 ) 0.00 0.00 Change in valuation allowance 0.60 0.00 0.00 Provision to return adjustments 0.46 0.00 0.00 Other 6.50 (0.04 ) 0.37 Pass through income not subject to tax (27.55 ) (18.27 ) 0.01 Effective income tax rate (0.12 %) 0.00 % 0.38 % As of December 31, 2020 and 2019, the HSE subsidiary had U.S. federal net operating loss carryforwards of approximately $0.6 million and $1.1 million, respectively, a portion of which expire at various dates through 2037, and a portion of which may be carried forward indefinitely. As of December 31, 2020 and 2019, HSE had U.S. state net operating loss carryforwards of approximately $0.6 million and $1.5 million, respectively, a portion of which expire at various dates through 2037, and a portion of which may be carried forward indefinitely. As of December 31, 2020, the Swedish Monocl subsidiaries had foreign net operating loss carryforwards of approximately $6.9 million, which may be available to offset future Swedish income tax liabilities and may be carried forward indefinitely. ASC 740 requires a valuation allowance to reduce the deferred tax assets reported if, based on the weight of the evidence, it is more likely than not that some portion or all of the deferred tax assets will not be realized. After consideration of all the evidence, both positive and negative, the Company has recorded a valuation allowance against the deferred tax assets of the Swedish Monocl subsidiaries at December 31, 2020, because the Company’s management has determined that it is more likely than not that the Company will not recognize the benefits of its foreign deferred tax assets primarily due to its historical loss position and, as a result, a valuation allowance of approximately $1.4 million has been established at December 31, 2020. The valuation allowance increased by approximately $1.4 million in the tax year ended December 31, 2020. The increase in valuation allowance for the year ended December 31, 2020 primarily related to the net operating losses in the Swedish Monocl subsidiary. Under the provisions of the Internal Revenue Code, the net operating loss and tax credit carryforwards are subject to review and possible adjustment by the Internal Revenue Service and state tax authorities. Net operating loss and tax credit carryforwards may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant shareholders over a three-year period in excess of 50 percent, as defined under Sections 382 and 383 of the Internal Revenue Code, respectively, as well as similar state provisions. This could limit the amount of tax attributes that can be utilized annually to offset future taxable income or tax liabilities. The amount of the annual limitation is determined based on the value of us immediately prior to the ownership change. Subsequent ownership changes may further affect the limitation in future years. In the future, the Company may complete financings that could result in a change in control, which will reduce the deferred tax assets for tax attributes the Company believes will expire unused due to the change in control limitations. On March 27, 2020, the Coronavirus Aid, Relief, and Economic Security (CARES) Act was signed into law making several changes to the Internal Revenue Code. The changes include but are not limited to: increasing the limitation on the amount of deductible interest expense, allowing companies to carryback certain net operating losses, and increasing the amount of net operating loss carryforwards that corporations can use to offset taxable income. The tax law changes in the Act did not have a material impact on the Company’s income tax provision. The Company will recognize interest and penalties related to uncertain tax positions in income tax expense. As of December 31, 2020, and 2019, there was no accrued interest or penalties related to uncertain tax positions and no such amounts have been recognized. The Company or one of its subsidiaries file income tax returns in the United States, and various state and foreign jurisdictions. The federal, state and foreign income tax returns are generally subject to tax examinations for the tax years ended December 31, 2017 through December 31, 2020. To the extent the Company has tax attribute carryforwards, the tax years in which the attribute was generated may still be adjusted upon examination by the Internal Revenue Service, state or foreign tax authorities to the extent utilized in a future period.

Loss Per Share

Loss Per Share	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Earnings Per Share [Abstract]
Loss Per Share	16. Loss Per Share Basic net loss per share of Class A Common Stock is computed by dividing net income attributable to Definitive Healthcare Corp. by the weighted-average number of shares of Class A Common Stock outstanding during the period, excluding unvested equity awards and subsidiary member units not exchanged. Diluted earnings per share of Class A Common Stock is calculated by dividing net income attributable to Definitive Healthcare Corp, adjusted for the assumed exchange of all potentially dilutive securities by the weighted-average number of shares of Class A Common Stock outstanding. Prior to the IPO, the Definitive OpCo membership structure included Class A and Class B member units. The Company analyzed the calculation of earnings per unit for periods prior to the IPO and determined that it resulted in values that would not be meaningful to the users of these unaudited consolidated financial statements. Therefore, earnings per share information has not been presented for the nine months ended September 30, 2020. The following table sets forth reconciliations of the numerators and denominators used to compute basic and diluted net loss per share of Class A Common Stock for the nine-months ended September 30, 2021. The basic and diluted earnings per share for the nine-months ended September 30, 2021 reflects only the period from September 15, 2021 to September 30, 2021, which represents the period wherein the Company had outstanding Class A Common Stock. (in thousands) Nine Months Ended 2021 Numerator: Net loss $ (46,493 ) Less: Net loss attributable to Definitive OpCo before Reorganization Transactions (33,343 ) Less: Net loss attributable to noncontrolling interests (5,172 ) Net loss attributable to Definitive Healthcare Corp. $ (7,978 ) The following table sets forth the computation of basic and diluted net loss per share of Class A Common Stock (per share amounts unaudited): (in thousands, except number of shares and per share amounts) Nine Months Ended 2021 Basic net loss per share attributable to common stockholders Numerator: Allocation of net loss attributable to Definitive Healthcare Corp. $ (7,978 ) Weighted average number of shares of Class A outstanding 88,263,333 Net loss per share, basic and diluted $ (0.09 ) Shares of the Company’s Class B Common Stock do not participate in the earnings or losses of Definitive Healthcare Corp. and are therefore not participating securities. As such, separate presentation of basic and diluted earnings per share of Class B Common Stock under the two-class The following table presents potentially dilutive securities excluded from the computation of diluted net loss per share for the period presented because their effect would have been anti-dilutive: Nine Months Ended Definitive OpCo Units 57,192,893	16. Net Loss per Unit The following table presents the calculation of basic and diluted net income/(loss) per unit (“EPU”) for the Company’s common units: Successor Company Year Ended Period from Net loss $ (51,157 ) $ (49,266 ) Weighted-average units used to compute basic and diluted net loss per unit 127,682,376 126,794,329 Net loss per unit, basic and diluted $ (0.40 ) $ (0.39 ) The Company has issued potentially dilutive instruments in the form of Class B Profit Interest Units granted to the Company’s employees. As of December 31, 2020, there were 474,920 vested Class B Profit Interest Units. The Company’s LLC operating agreement precludes Class B members from participating in distributions until Class A members’ capital contributions have been recovered and until performance hurdle rates have been exceeded. The Company does not include any of these instruments in its calculation of diluted loss per unit during the period from July 16, 2019 to December 31, 2019 (Successor) and for the year ended December 31, 2020 (Successor) because to include them would be anti-dilutive due to the Company’s net loss during the period.

Segment and Geographic Data

Segment and Geographic Data	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Segment Reporting [Abstract]
Segment and Geographic Data	17. Segment and Geographic Data The Company operates as one operating segment. Operating segments are defined as components of the Company for which separate financial information is available and evaluated regularly by the Company’s chief operating decision maker in deciding how to allocate resources and in assessing performance. The chief operating decision maker for the Company is the chief executive officer. The chief executive officer reviews financial information presented on a consolidated basis, accompanied by information about revenue by type of service and geographic region, for purposes of allocating resources and evaluating financial performance. Revenues by geographic area presented based upon the location of the customer are as follows: For the Nine Months Ended September 30, (in thousands) 2021 2020 United States $ 114,339 $ 84,659 Rest of world 5,502 — Total revenues $ 119,841 $ 84,659 For a summary of our revenue disaggregated by service, refer to Note 4. Revenue Long-lived assets by geographical region are based on the location of the legal entity that owns the assets. Long-lived assets by geographic area presented based upon the location of the assets are as follows: (in thousands) September 30, 2021 December 31, 2020 United States $ 4,311 $ 3,120 Rest of world 386 128 Total long-lived assets $ 4,697 $ 3,248	17. Segment and Geographic Data The Company operates as one operating segment. Operating segments are defined as components of the Company for which separate financial information is available and evaluated regularly by the Company’s chief operating decision maker in deciding how to allocate resources and in assessing performance. The chief operating decision maker for the Company is the chief executive officer. The chief executive officer reviews financial information presented on a consolidated basis, accompanied by information about revenue by type of service and geographic region, for purposes of allocating resources and evaluating financial performance. Revenues by geographic area presented based upon the location of the customer are as follows (in thousands): Successor Company Predecessor Year Ended Period from Period from United States $ 117,755 $ 40,045 $ 45,458 Rest of world 562 — — Total revenues $ 118,317 $ 40,045 $ 45,458 For a summary of our revenue disaggregated by service, refer to Note 4. Revenue Long-lived assets by geographical region are based on the location of the legal entity that owns the assets. Long-lived assets by geographic area presented based upon the location of the assets are as follows (in thousands): Successor Company December 31, 2020 December 31, 2019 United States $ 3,120 $ 2,558 Rest of world 128 — Total long-lived assets $ 3,248 $ 2,558

Related Parties

Related Parties	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Related Party Transactions [Abstract]
Related Parties	18. Related Parties The Company has engaged in revenue transactions within the ordinary course of business with entities affiliated with its private equity sponsors and with members of the Company’s board of directors. During each of the nine months ended September 30, 2021 and 2020 the Company recorded revenue of $0.7 million and $0.6 million, respectively. The associated receivable for the revenue transactions amounted to million and $0.7 million at September 30, 2021 and December 31, 2020, respectively. The Company reimburses its private equity sponsors for services and any related travel and out-of-pocket out-of-pocket On September 17, 2021, Definitive OpCo entered into an agreement to reimburse approximately $0.9 million in aggregate documented expenses incurred by Advent International, 22C Capital LLC (“22C Capital”), Spectrum Equity Management, L.P. (“Spectrum Equity”), Jason Krantz and MHDH AB and in connection with the Reorganization Transactions. The amounts were included in accrued expenses and other current liabilities as of September 30, 2021 and are expected to be paid in the fourth quarter of 2021. D .	18. Related Parties The Company reimburses its private equity sponsors for services and any related travel and out-of-pocket expenses. During the years ended December 31, 2020, and 2019, the Company had expenses for services, travel and out-of-pocket expenses to its private equity sponsors of $0.1 million and $0.0 million, respectively. The associated payable for the service transactions was de minimis at December 31, 2020 and 2019. The Company has engaged in revenue transactions within the ordinary course of business with entities affiliated with its private equity sponsors and with members of the Company’s board of directors. During the years ended December 31, 2020, and 2019 the Company recorded revenue of $0.4 million and $0.2 million, respectively. The associated receivables for the revenue transactions were $0.1 million and $0.1 million at December 31, 2020 and 2019, respectively.

Noncontrolling Interest

Noncontrolling Interest	9 Months Ended
	Sep. 30, 2021
Noncontrolling Interest [Abstract]
Noncontrolling Interest	19. Noncontrolling Interest Definitive Healthcare Corp. operates and controls all of the business and affairs of Definitive OpCo, and through Definitive OpCo and its subsidiaries, conducts its business. Accordingly, Definitive Healthcare Corp. consolidates the financial results of Definitive OpCo, and reports the noncontrolling interests of its consolidated subsidiaries on its consolidated financial statements based on the Definitive OpCo Units held by Continuing LLC Members. Changes in Definitive Healthcare Corp.’s ownership interest in its consolidated subsidiaries are accounted for as equity transactions. As such, future redemptions or direct exchanges of OpCo Units by Continuing LLC Members will result in a change in ownership and reduce or increase the amount recorded as Noncontrolling interests and increase or decrease Additional paid-in capital in the Company’s Condensed Consolidated Balance Sheets. As of September 30, 2021, Definitive Healthcare Corp. held 88,263,333 units in the Definitive OpCo resulting in an ownership interest of .

Subsequent Events

Subsequent Events	May 24, 2021	Sep. 30, 2021	Dec. 31, 2020
Subsequent Events [Abstract]
Subsequent Events	4. Subsequent Events The Corporation has evaluated subsequent events through May 28, 2021, the date which the financial statement was issued, and did not identify any additional matters that require disclosure.	20. Subsequent Events Robert Musslewhite was appointed as President of Definitive Healthcare Corp. effective October 7, 2021. In connection with his appointment, Mr. Musslewhite entered into an employment agreement pursuant to which, he will be paid an annual base salary of $0.4 million. Mr. Musslewhite’s annual bonus will equal 68% of his pro-rated executives. In addition, pursuant one-year one-year	19. Subsequent Events The Company has evaluated subsequent events through May 28, 2021, the date which the consolidated financial statements were issued, and did not identify any additional matters that require disclosure.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	May 24, 2021	Sep. 30, 2021	Dec. 31, 2020
Basis of Presentation	Basis of Accounting The Balance Sheet has been prepared in accordance with generally accepted accounting principles in the United States (“U.S. GAAP”). Separate statements of operations, changes in stockholders’ equity and cash flows have not been presented in the financial statement because there have been no activities in this entity or because the single transaction is fully disclosed below.	Basis of Presentation The accompanying unaudited condensed consolidated statements Refer to Note 2. Summary of Significant Accounting	Basis of Presentation The consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”). The Financial Accounting Standards Board (“FASB”) establishes these principles to ensure financial condition, results of operations, and cash flows are consistently reported. Any reference in these notes to applicable accounting guidance is meant to refer to the authoritative nongovernmental GAAP as found in the FASB Accounting Standards Codification (“ASC”).
Principles of Consolidation			Principles of Consolidation The consolidated financial statements include the accounts of the Company and its consolidated subsidiaries. All significant intercompany accounts and transactions have been eliminated in consolidation.
Use of Estimates in the Preparation of Financial Statements			Use of Estimates in the Preparation of Financial Statements The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates, judgements, and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements, as well as the reported amounts of revenues and expenses during the reporting period. These estimates relate, but are not limited to, revenue recognition, allowance for doubtful accounts, contingencies, valuations and useful lives of intangible assets acquired in business combinations, equity-based compensation, and income taxes. Actual results could differ from those estimates.
Revenue Recognition			Revenue Recognition The Company derives revenue primarily from subscription license fees charged for access to the Company’s database platform, and professional services. The customer arrangements include a promise to allow customers to access subscription license to the database platform which is hosted by the Company over the contract period, without allowing the customer to take possession of the subscription license or transfer hosting to a third party. The Company recognizes revenue in accordance with ASC 606– Revenue from Contracts with Customers Revenue related to hosted subscription license arrangements, which often include non-distinct non-cancellable. The Company also enters into a limited number of contracts that can include various combinations of professional services, which are generally capable of being distinct and can be accounted for as separate performance obligations. Revenue related to these professional services is insignificant and is recognized at a point in time, when the performance obligations under the terms of the contract are satisfied and control has been transferred to the customer. When a contract contains multiple performance obligations, the contract transaction price is allocated on a relative standalone selling price (“SSP”) basis to each performance obligation. The Company typically determines SSP based on observable selling prices of its products and services. In instances where SSP is not directly observable, SSP is determined using information that may include market conditions and other observable inputs, or by using the residual approach. The Company accounts for an arrangement when it has approval and commitment from both parties, the rights are identified, the contract has commercial substance, and collectability of consideration is probable. The Company generally obtains written purchase contracts from its customers for a specified service at a specified price, with a specified term, which constitutes an arrangement. Revenue is recognized at the amount expected to be collected, net of any taxes collected from customers, which are subsequently remitted to governmental authorities. The timing of revenue recognition may not align with the right to invoice the customer, but the Company has determined that in such cases, a significant financing component generally does not exist. The Company has elected the practical expedient that permits an entity not to recognize a significant financing component if the time between the transfer of a good or service and payment is one year or less. Payment terms on invoiced amounts are typically 30 days. The Company does not offer rights of return for its products and services in the normal course of business, and contracts generally do not include customer acceptance clauses. The Company arrangements typically do not contain variable consideration. However, certain contracts with customers may include service level agreements that entitle the customer to receive service credits, and in certain
Fair Value Measurements			Fair Value Measurements The Company measures assets and liabilities at fair value based on an expected exit price, which represents the amount that would be received on the sale of an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value may be based on assumptions that market participants would use in pricing an asset or liability. The authoritative guidance on fair value measurements establishes a consistent framework for measuring fair value on either a recurring or nonrecurring basis whereby inputs, used in valuation techniques, are assigned a hierarchical level as follows: Level 1 - Observable inputs that reflect unadjusted quoted prices in active markets for identical assets or liabilities Level 2 - Other inputs that are directly or indirectly observable in the marketplace Level 3 - Unobservable inputs that are supported by little or no market activity, including the Company’s own assumptions in determining fair value.
Cash and Cash Equivalents			Cash and Cash Equivalents The Company considers all short-term, highly liquid investments with an original maturity of three months or less to be cash and cash equivalents.
Concentration of Credit Risk and Significant Customers			Concentration of Credit Risk and Significant Customers Financial instruments that potentially subject the Company to concentrations of credit risk consist principally of cash and cash equivalents and accounts receivable. The Company holds cash at major financial institutions that often exceed Federal Deposit Insurance Corporation (“FDIC”) insured limits. The Company manages its credit risk associated with cash concentrations by concentrating its cash deposits in high quality financial institutions and by periodically evaluating the credit quality of the primary financial institutions holding such deposits. The carrying value of cash approximates fair value. Historically, the Company has not experienced any losses due to such cash concentrations. The Company does not have any off-balance-sheet Concentrations of credit risk with respect to trade account receivables are limited due to the large number of customers comprising the Company’s customer base. No single customer accounted for more than 10% of total net sales or accounts receivable in 2020 and 2019.
Accounts Receivable, Net and Contract Assets			Accounts Receivable, Net and Contract Assets Accounts receivable are stated at the amount management expects to collect from outstanding balances. Allowances for doubtful accounts are provided for those outstanding balances considered to be uncollectible based upon historical collection experience, changes in customer payment profiles, the aging of receivable balances, and management’s overall evaluation of the outstanding balances at year end. Balances that are still outstanding after management has made reasonable collection efforts are written off through a charge to the allowance for doubtful accounts. At December 31, 2020 and 2019, the allowance for doubtful accounts was $0.9 million and $0.5 million, respectively.
Deferred Contract Costs			Deferred Contract Costs Certain sales commissions earned by the Company’s employees are considered incremental and recoverable costs of obtaining a contract with a customer. These sales commissions for initial and renewal contracts are capitalized and are included in current portion of deferred contract costs and deferred contract costs, net of current portion. Capitalized amounts also include the associated payroll taxes and other fringe benefits associated with the payments to the Company’s employees. Costs capitalized related to new revenue contracts are amortized on a straight-line basis over four years, which reflects the average period of benefit, including expected contract renewals. When determining the period of benefit, the Company primarily considered its initial estimated customer life, the technological life of the subscription license, as well as an estimated customer relationship period. Costs capitalized related to renewal contracts are amortized on a straight-basis over 2 years, which reflects the average renewal period. Renewal contracts with a term of one year or less are expensed. The capitalized amounts are recoverable through future revenue streams under all non-cancellable
Property and Equipment, Net			Property and Equipment, Net Property and equipment are stated at cost, net of accumulated depreciation and amortization. The assets are depreciated on a straight-line basis over the estimated useful lives as follows: Furniture and equipment 5 years Computers and software 3 years Leasehold improvements Lesser of the asset life or lease term Upon retirement or sale, the cost of assets disposed and the related accumulated depreciation are removed from the accounts and any resulting gain or loss is recognized as gain or loss on disposal of assets in the consolidated statements of income (loss). Major replacements and improvements are capitalized, while general repairs and maintenance are charged to expense as incurred.
Advertising and Promotional Expenses			Advertising and Promotional Expenses The Company expenses advertising costs as incurred in accordance with ASC 720— Other Expenses – Advertising Cost
Software Development Costs			Software Development Costs The Company accounts for its software development costs in accordance with the guidance set forth in ASC 350-40, Intangibles – Goodwill and Other – Internal Use Software.
Business Combinations			Business Combinations The Company accounts for business combinations using the acquisition method in accordance with ASC 805, Business Combinations The estimates are inherently uncertain and subject to revision as additional information is obtained during the measurement period for an acquisition, which may last up to one year from the acquisition date. During the measurement period, the Company may record adjustments to the fair value of tangible and intangible assets acquired and liabilities assumed, with a corresponding offset to goodwill. After the conclusion of the measurement period or the final determination of the fair value of assets acquired or liabilities assumed, whichever comes first, any subsequent adjustments are recorded to earnings. In addition, uncertain tax positions and tax-related For any given acquisition, the Company may identify certain pre-acquisition
Goodwill and Intangible Assets			Goodwill and Intangible Assets Goodwill is calculated as the excess of the purchase consideration paid in the acquisition of a business over the fair value of the identifiable assets acquired and liabilities assumed. Goodwill is not amortized and is tested for impairment at the reporting unit level, at least annually, and more frequently if events or circumstances occur that would indicate a potential decline in fair value. A reporting unit is an operating segment or a component of an operating segment. The Company first assesses qualitative factors to evaluate whether it is more likely than not that the fair value of a reporting unit is less than the carrying amount, or it may elect to bypass such assessment. If it is determined that it is more likely than not that the fair value of the reporting unit is less than its carrying value, or if the Company elects to bypass the qualitative assessment, management will perform a quantitative test by determining the fair value of the reporting unit. The estimated fair value of the reporting unit is based on a projected discounted cash flow model that includes significant assumptions and estimates, including the discount rate, growth rate, and future financial performance. Valuations of similarly situated public companies are also evaluated when assessing the fair value of the reporting unit. If the carrying value of the reporting unit exceeds the fair value, then a goodwill impairment loss is recognized for the difference. The Company performs its annual impairment assessment in the first month of the fourth quarter of each calendar year. Definite-lived intangible assets are amortized over their estimated useful lives, Customer relationships 14 – 15 years Technology 7 – 8 years Tradenames / trademark 17 – 19 years Data 1– 4 years
Impairment of Long-Lived Assets			Impairment of Long-Lived Assets The Company reviews the carrying value of property and equipment and other long-lived assets, including definite-lived intangible assets and property and equipment, for impairment whenever events and circumstances indicate that the carrying value of an asset may not be recoverable. If estimated undiscounted future cash flows expected to result from its use and eventual disposition are not expected to be adequate to recover the asset’s carrying value, an impairment charge is recorded for the excess of the asset’s carrying value over its estimated fair value.
Deferred Revenue		Deferred Revenue Deferred revenue consists of customer payments and billings in advance of revenue being recognized from the subscription services. If revenue has not yet been recognized, a contract liability (deferred revenue) is recorded. Deferred revenue that is anticipated to be recognized within the next 12 months is recorded as current portion of deferred revenue and the remaining portion is included in deferred revenue on the consolidated balance sheets.
Debt Issuance Costs			Debt Issuance Costs Costs incurred in connection with the issuance of long-term debt are deferred and amortized as interest expense over the terms of the related debt using the effective interest method for term debt and on a straight-line basis for revolving debt. To the extent that the debt is outstanding, these amounts are reflected in the consolidated balance sheets as direct deductions from the long-term portions of debt, except for the costs related to the Company’s revolving credit facilities, which are presented as a non-current non-revolving
Deferred Initial Public Offering Costs			Deferred Initial Public Offering Costs The Company capitalizes deferred initial public offering (“IPO”) costs, which primarily consist of direct, incremental legal, professional, accounting and other third-party fees relating to the Company’s initial public offering, within other non-current
Sales Tax			Sales Tax The Company’s revenues may be subject to local sales taxes in certain states, if applicable. It is the Company’s policy to treat all such taxes on a “net” basis, which means the charges for sales taxes to the Company’s customers are not included in revenues and the remittance of such taxes is not presented as an expense.
Income Taxes			Income Taxes AIDH TopCo, LLC is taxed as a partnership. Definitive Healthcare Holdings, LLC is a wholly owned subsidiary of AIDH TopCo, LLC and is treated as a disregarded entity for income tax purposes. Accordingly, for federal and state income tax purposes, income, losses, and other tax attributes not generated by the HSE or Monocl subsidiaries pass through to the AIDH TopCo, LLC members’ income tax returns. The Company may be subject to certain taxes on behalf of its members in certain states. Definitive Healthcare Holdings was not subject to any federal income taxes for the tax years ended December 31, 2020 and 2019, nor was it subject to state income taxes in certain jurisdictions for the tax years ended December 31, 2020 and 2019. HSE and the Monocl US subsidiaries are taxed as corporations. Accordingly, these entities account for income taxes by recognizing tax assets and liabilities for the cumulative effect of all the temporary differences between financial statement carrying amounts and the tax basis of assets and liabilities. The foreign tax provision pertains to foreign income taxes due at the Swedish Monocl subsidiaries. Deferred taxes for the HSE, Monocl US and Swedish subsidiaries are determined using enacted federal, state, or foreign income tax rates in effect in the year in which the differences are expected to reverse. Valuation allowances are provided if based upon the weight of available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. The Company has provided for these taxes. The aggregate of such taxes is not material and is included in general and administrative in the accompanied statement of operations. Under the provisions of ASC 740 , Income Taxes
Net Loss Per Unit			Net Loss Per Unit Net income or loss per unit is computed in conformity with the two-class two-class two-class Basic net income or loss per unit is computed by dividing the net income or loss by the weighted-average number of common units of the Company outstanding during the period. Diluted net income or loss per unit is computed by giving effect to all potential units of common units, including outstanding incentive units, to the extent dilutive. The Company uses the treasury stock method to calculate potentially dilutive shares, as if they were converted into common stock at the beginning of the period. Basic and diluted net income or loss per unit was the same for each period presented as the inclusion of all potential units of common units outstanding would have been anti-dilutive. All net earnings (loss) for the Predecessor period from January 1, 2019 to July 15, 2019 were entirely allocable to Predecessor members. Additionally, due to the impact of the Definitive Holdco Acquisition, the Company’s capital structure for the Predecessor and Successor periods is not comparable. As a result, the presentation of earnings (loss) per share for the periods prior to such transaction is not meaningful and only earnings (loss) per unit for periods subsequent to the Definitive Holdco Acquisition are presented herein. See Note 16. Net Loss Per Unit
Equity-based Compensation			Equity-based Compensation The Company periodically grants equity units to employees, consultants, directors, managers, or others providing service. These units are considered profit interests, which in general, entitle the holder of the unit to a pro rata share of the increase in fair value of the unit over the base value, which is determined at the award date, and are deemed to be equity instruments. Certain units have time-based and performance-based vesting criteria. The Company accounts for these profit interest units in accordance with ASC 718— Compensation – Stock Compensation. The Company classifies equity-based compensation expense in its consolidated statements of (loss) income in the same manner in which the award recipient’s salary and related costs are classified.
Adoption of Recently Issued Financial Accounting Standards		Adoption of Recently Issued Financial Accounting Standards In August 2018, the FASB issued ASU No. 2018-15— Intangibles — Goodwill and Other — Internal-Use 350-40), internal-use impact	Adoption of Recently Issued Financial Accounting Standards In May 2014, the FASB issued ASC 606— Revenue from Contracts with Customers 340-40, Other Assets and Deferred Costs – Contracts with Customers The Company adopted ASC 606 effective January 1, 2019 under the modified retrospective method, which resulted in an adjustment at January 1, 2019 of $5.4 million to members’ capital for the cumulative effect of applying the standard to all contracts not completed as of the adoption date. The adjustment primarily related to deferred contract costs, including incremental employee sales commissions and other employee compensation arrangements, and adjustments to deferred and unbilled revenues of $4.3 million and $1.1 million, respectively. The cost of all incremental commissions and other employee compensation arrangements are deferred and amortized on a straight-line basis over the expected period of benefit, generally between two and four years. The deferred and unbilled revenues were adjusted upon adoption to better align the recognition of revenues with the timing of transfer of control to the customer. The cumulative effect of applying the new guidance was recorded as an adjustment to members’ capital as of the adoption date. As a result of applying the modified retrospective method to adopt the new revenue guidance, the following adjustments were made to the consolidated balance sheet as of January 1, 2019. As reported ASC 606 As Adjusted Consolidated Balance Sheet: Accounts receivable, net $ 14,932 $ 367 $ 15,299 Current portion of deferred contract costs — 1,346 1,346 Total current assets 35,176 1,713 36,889 Deferred contract costs, net of current portion — 2,973 2,973 Total assets $ 87,061 $ 4,686 $ 91,747 Current portion of deferred revenue 32,187 (729 ) 31,458 Total current liabilities 36,676 (729 ) 35,947 Total liabilities 36,676 (729 ) 35,947 Members’ capital 50,385 5,415 55,800 Total liabilities and members’ capital $ 87,061 $ 4,686 $ 91,747 The following tables compare the reported consolidated balance sheet as of December 31, 2019 and statements of (loss) income for the periods from July 16, 2019 to December 31, 2019 and January 1, 2019 to July 15, 2019, to the adjusted amounts had ASC 605 , As Reported Adjustments As Adjusted Consolidated Balance Sheet: Accounts receivable, net $ 25,021 $ (250 ) $ 24,771 Current portion of contract assets 769 (769 ) — Total current assets 36,107 (1,019 ) 35,088 Contract assets, net of current portion 2,116 (2,116 ) — Total assets 1,721,154 (3,135 ) 1,718,019 Current portion of deferred revenue 45,977 990 46,967 Total current liabilities 69,917 990 70,907 Total liabilities 504,914 990 505,904 Members’ capital (deficit) 1,216,240 (4,125 ) 1,212,115 Total liabilities and members’ capital (deficit) $ 1,721,154 $ (3,135 ) $ 1,718,019 Predecessor Company As Reported Period from January 1, Adjustments As Adjusted Period from January 1, Revenue $ 45,458 $ (79 ) $ 45,379 Total cost of revenue 5,328 — 5,328 Gross profit 40,130 (79 ) 40,051 Sales and marketing 16,039 1,416 17,455 Total operating expenses 27,097 1,416 28,513 Income (loss) from operations 13,033 (1,495 ) 11,538 Total other expense, net (165 ) — (165 ) Net income (loss) $ 12,868 $ (1,495 ) $ 11,373 Successor Company As Reported Period from July 16, 2019 to December 31, 2019 Adjustments As Adjusted Period from July 16, 2019 to December 31, Revenue $ 40,045 $ (66 ) $ 39,979 Total cost of revenue 13,282 — 13,282 Gross profit 26,763 (66 ) 26,697 Sales and marketing 10,814 2,885 13,699 Total operating expenses 57,825 2,885 60,710 Loss from operations (31,062 ) (2,951 ) (34,013 ) Total other expense, net (18,204 ) — (18,204 ) Net loss $ (49,266 ) $ (2,951 ) $ (52,217 ) In January 2017, the FASB issued ASU No. 2017-04 —Goodwill and Other (Topic 350) – Simplifying the Test for Goodwill Impairment. 2017-04 In June 2018, the FASB issued ASU No. 2018-07 —Compensation—Stock Compensation (Topic 718), Improvements to Nonemployee Share-based Payment Accounting
Recently-Issued Accounting Pronouncements Not Yet Adopted		Recently-Issued Accounting Pronouncements Not Yet Adopted In February 2016, the FASB issued ASU 2016-02— Leases recording a cumulative effect adjustment as of the adoption date, with certain practical expedients available. The Company, as an Emerging Growth Company as defined by the Jumpstart Our Business Startups Act of 2012 (the “JOBS Act”), can elect to take the extended transition period and adopt the standard following guidance for non-public The Company will adopt ASU 2016-02 2018-11, non-lease . In June 2016, the FASB issued ASU No. 2016-13— Financial Instruments Credit Losses (Topic 326) Measurement of Credit Losses on Financial Instruments In December 2019, the FASB issued ASU No. 2019-12— Income Taxes (Topic 740), Simplifying the Accounting for Income Taxes. In March 2020, the FASB issued ASU No. 2020-04— Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting No. 2020-04	Recently-Issued Accounting Pronouncements Not Yet Adopted In February 2016, the FASB issued ASU 2016-02— Leases right-of-use In June 2016, the FASB issued ASU No. 2016-13 —Financial Instruments—Credit Losses (Topic 326)—Measurement of Credit Losses on Financial Instruments. In August 2018, the FASB issued ASU No. 2018-15— Intangibles—Goodwill and Other—Internal-Use 350-40), implementation costs incurred to develop or obtain internal-use In December 2019, the FASB issued ASU No. 2019-12— Income Taxes (Topic 740), Simplifying the Accounting for Income Taxes In March 2020, the FASB issued ASU No. 2020-04— Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting No. 2020-04

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Scheudle Of Changes On Balance Sheet And Income Statement Due To The Adoption Of New Accounting pronouncements	As a result of applying the modified retrospective method to adopt the new revenue guidance, the following adjustments were made to the consolidated balance sheet as of January 1, 2019. As reported ASC 606 As Adjusted Consolidated Balance Sheet: Accounts receivable, net $ 14,932 $ 367 $ 15,299 Current portion of deferred contract costs — 1,346 1,346 Total current assets 35,176 1,713 36,889 Deferred contract costs, net of current portion — 2,973 2,973 Total assets $ 87,061 $ 4,686 $ 91,747 Current portion of deferred revenue 32,187 (729 ) 31,458 Total current liabilities 36,676 (729 ) 35,947 Total liabilities 36,676 (729 ) 35,947 Members’ capital 50,385 5,415 55,800 Total liabilities and members’ capital $ 87,061 $ 4,686 $ 91,747 The following tables compare the reported consolidated balance sheet as of December 31, 2019 and statements of (loss) income for the periods from July 16, 2019 to December 31, 2019 and January 1, 2019 to July 15, 2019, to the adjusted amounts had ASC 605 , As Reported Adjustments As Adjusted Consolidated Balance Sheet: Accounts receivable, net $ 25,021 $ (250 ) $ 24,771 Current portion of contract assets 769 (769 ) — Total current assets 36,107 (1,019 ) 35,088 Contract assets, net of current portion 2,116 (2,116 ) — Total assets 1,721,154 (3,135 ) 1,718,019 Current portion of deferred revenue 45,977 990 46,967 Total current liabilities 69,917 990 70,907 Total liabilities 504,914 990 505,904 Members’ capital (deficit) 1,216,240 (4,125 ) 1,212,115 Total liabilities and members’ capital (deficit) $ 1,721,154 $ (3,135 ) $ 1,718,019 Predecessor Company As Reported Period from January 1, Adjustments As Adjusted Period from January 1, Revenue $ 45,458 $ (79 ) $ 45,379 Total cost of revenue 5,328 — 5,328 Gross profit 40,130 (79 ) 40,051 Sales and marketing 16,039 1,416 17,455 Total operating expenses 27,097 1,416 28,513 Income (loss) from operations 13,033 (1,495 ) 11,538 Total other expense, net (165 ) — (165 ) Net income (loss) $ 12,868 $ (1,495 ) $ 11,373 Successor Company As Reported Period from July 16, 2019 to December 31, 2019 Adjustments As Adjusted Period from July 16, 2019 to December 31, Revenue $ 40,045 $ (66 ) $ 39,979 Total cost of revenue 13,282 — 13,282 Gross profit 26,763 (66 ) 26,697 Sales and marketing 10,814 2,885 13,699 Total operating expenses 57,825 2,885 60,710 Loss from operations (31,062 ) (2,951 ) (34,013 ) Total other expense, net (18,204 ) — (18,204 ) Net loss $ (49,266 ) $ (2,951 ) $ (52,217 )

Business Combinations (Tables)

Business Combinations (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Business Acquisition [Line Items]
Schedule of Proforma Information Related to Business Combination		Unaudited Pro Forma Supplementary Data (in thousands) Year Ended Revenue $ 84,122 Net loss (92,228 )
Schedule of Reconciliation of Purchase Price to the Capital Contribution		The following table reconciles the purchase price to the capital contribution made by Sponsor as July 16, 2019 (in thousands): Total purchase price $ 1,699,612 Transaction costs paid from proceeds 4,004 Less Debt Financing 436,359 Capital Contribution $ 1,267,257
Monocl Holding Company
Business Acquisition [Line Items]
Schedule of Consideration Transferred in Business Combination	On October 27, 2020, the Company completed the purchase of all outstanding shares of Monocl for a total estimated consideration of $46.3 million , summarized as follows: (in thousands) Cash consideration $ 18,307 Equity issuance 25,439 Contingent consideration 2,600 Purchase price $ 46,346	The consideration transferred for the transaction is summarized as follows (in thousands): Cash consideration $ 18,307 Equity issuance 25,439 Contingent consideration 2,600 Purchase price $ 46,346
Schedule of Recognized Assets and Libailities Pertaining to Business Combination	The purchase accounting for the Monocl acquisition was finalized as of December 31, 2020. The fair values assigned to tangible and identified intangible assets acquired and liabilities assumed were based on management’s estimates and assumptions. The final allocation of the acquisition-date fair values of assets and liabilities as of December 31, 2020, was as follows: (in thousands) Preliminary allocation: October 27, Cash $ 2,774 Accounts receivable 788 Prepaid expenses and other current assets 614 Property and equipment 20 Intangible assets 18,900 Accounts payable and accrued expenses (2,137 ) Deferred revenue (2,884 ) Total assets acquired and liabilities assumed 18,075 Goodwill 28,271 Purchase price $ 46,346	The final allocation of the acquisition-date fair values of assets and liabilities pertaining to this business combination as of December 31, 2020, was as follows (in thousands): October 27, 2020 Cash $ 2,774 Accounts receivable 788 Prepaid expenses and other current assets 614 Property and equipment 20 Intangible assets 18,900 Accounts payable and accrued expenses (2,137 ) Deferred revenue (2,884 ) Total assets acquired and liabilities assumed 18,075 Goodwill 28,271 Purchase price $ 46,346
Schedule of Proforma Information Related to Business Combination	Unaudited Pro Forma Supplementary Data: Nine Months Ended (in thousands) Revenue $ 91,750 Net loss (43,763 )	Unaudited Pro Forma Supplementary Data (in thousands) Year Ended Year Ended Revenue $ 122,333 $ 87,157 Net loss (58,350 ) (97,134 )
Definitive Holdco
Business Acquisition [Line Items]
Schedule of Consideration Transferred in Business Combination		The consideration transferred for the transaction is summarized as follows (in thousands): Cash consideration $ 1,129,346 Common units issued 570,266 Purchase price $ 1,699,612
Schedule of Recognized Assets and Libailities Pertaining to Business Combination	The purchase accounting for the Definitive Holdco Acquisition, was finalized as of July 16, 2020. The final allocation of the acquisition-date fair values of assets and liabilities pertaining to this business combination as of July 16, 2020, was as follows (in thousands). Predecessor Successor Company Carrying Fair Value Final Cash $ 17,058 $ — $ 17,058 Accounts receivable 12,747 — 12,747 Deferred contract costs 5,735 (5,735 ) — Prepaid expenses and other current assets 1,539 150 1,689 Other assets 49 — 49 Property and equipment 2,201 — 2,201 Intangible assets 19,108 456,292 475,400 Accounts payable and accrued expenses (5,477 ) 684 (4,793 ) Deferred revenue (38,278 ) 6,278 (32,000 ) Total assets acquired and liabilities assumed 14,682 457,669 472,351 Goodwill $ 82,767 $ 1,144,494 1,227,261 Total purchase price $ 1,699,612 The adjustments set forth in the following consolidated balance sheet as of July 15, 2019, reflect the effect of the Debt Financing and Finance Merger (reflected in the column “Debt Financing / Finance Merger”), and the fair value adjustments to assets acquired and liabilities assumed, as a result of the purchase accounting, in connection with the Definitive Holdco Acquisition (reflected in the column “Fair Value Adjustments”) (in thousands): Predecessor Debt Fair Value Successor July 16, 2019 Cash $ 17,058 $ — $ — $ 17,058 Accounts receivable 12,747 — — 12,747 Prepaid expenses and other current assets 1,539 16 150 1,705 Deferred contract costs 5,735 — (5,735 ) — Property and equipment 2,201 — — 2,201 Intangible assets 19,108 — 456,292 475,400 Goodwill 82,767 — 1,144,494 1,227,261 Other assets 49 14,589 — 14,638 Total assets $ 141,204 $ 14,605 $ 1,595,201 $ 1,751,010 Accounts payable and accrued expenses $ 5,477 $ 10,407 $ (684 ) $ 15,200 Deferred revenue 38,278 — (6,278 ) 32,000 Term Loan — 436,553 — 436,553 Total liabilities 43,755 446,960 (6,962 ) 483,753 Members’ Capital 97,449 (432,355 ) 1,602,163 1,267,257 Total liabilities and equity $ 141,204 $ 14,605 $ 1,595,201 $ 1,751,010

Revenue (Tables)

Revenue (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Schedule of Disaggregation of Revenue	The following table represents a disaggregation of revenue from arrangements with customers for the nine months ended September 30, 2021 and 2020, respectively: Nine Months Ended (in thousands) 2021 2020 Platform subscriptions $ 118,545 $ 83,814 Professional services 1,296 845 Total revenue $ 119,841 $ 84,659	The following table represents a disaggregation of revenue from arrangements with customers for the year ended December 31, 2020 (Successor) and the periods from July 16, 2019 to December 31, 2019 (Successor) and January 1, 2019 to July 15, 2019 (Predecessor) (in thousands). Successor Company Predecessor Year Ended Period from Period from Platform subscriptions $ 117,080 $ 39,872 $ 45,244 Professional services 1,237 173 214 Total revenue $ 118,317 $ 40,045 $ 45,458
Schedule of Opening and Closing Balances of Receivables Deferred Contract Costs and Contract Liabilities	The opening and closing balances of the Company’s receivables, deferred contract costs and contract liabilities from contracts with customers are as follows: (in thousands) September 30, December 31, Accounts receivable, net $ 27,886 $ 33,108 Deferred contract costs 5,359 2,947 Long-term deferred contract costs 9,388 5,952 Deferred revenues 70,179 61,200	The opening and closing balances of the Company’s receivables, deferred contract costs and contract liabilities from contracts with customers are as follows (in thousands): Successor Company Predecessor December 31, December 31, July 16, July 15, January 1, Accounts receivables, net $ 33,108 $ 25,021 $ 12,747 $ 12,747 $ 15,299 Deferred contract costs 2,947 769 — 1,906 1,346 Long-term deferred contract costs 5,952 2,116 — 3,829 2,973 Deferred revenues $ 61,200 $ 46,125 $ 32,000 $ 38,278 $ 31,458
Schedule of Activity Impacting the Deferred Contract Costs	A summary of the activity impacting the deferred contract costs for the nine months ended September 30, 2021 and the year ended December 31, 2020 is presented below: (in thousands) September 30, December 31, Balance at beginning of period $ 8,899 $ 2,885 Costs amortized (3,195 ) (1,670 ) Additional amounts deferred 9,043 7,684 Balance at end of period 14,747 8,899 Classified as: Current 5,359 2,947 Non-current 9,388 5,952 Total $ 14,747 $ 8,899	A summary of the activity impacting the deferred contract costs during the year ended December 31, 2020 and the periods from July 16, to December 31, 2019 (Successor) and January 1, 2019 to July 15, 2019 (Predecessor) is presented below (in thousands): Successor Company Predecessor Year Ended Period from Period from Balance at beginning of period $ 2,885 $ 5,735 $ — Adoption of ASC 606 — — 4,320 Costs amortized (1,670 ) (189 ) (824 ) Additional amounts deferred 7,684 3,074 2,239 Acquisition-related adjustment — (5,735 ) Balance at end of period $ 8,899 $ 2,885 $ 5,735 Classified as: Current 2,947 769 — Non-current 5,952 2,116 — Total deferred contract costs (deferred commissions) $ 8,899 $ 2,885 $ —
Schedule of Activity Impacting Deferred Revenue Balances	A summary of the activity impacting deferred revenue balances during the nine months ended September 30, 2021 and for the year ended December 31, 2020 is presented below: (in thousands) September 30, December 31, Balance at beginning of period $ 61,200 $ 46,125 Revenue recognized (119,841 ) (118,317 ) Additional amounts deferred 128,820 133,392 Balance at end of period $ 70,179 $ 61,200	A summary of the activity impacting deferred revenue balances during the year ended December 31, 2020 and the periods from July 16, 2019 to December 31, 2019 and January 1, 2019 to July 15, 2019, is presented below (in thousands): Successor Company Predecessor Year Ended Period from Period from Balance at beginning of period $ 46,125 $ 38,278 $ 32,187 Adoption of ASC 606 — — (729 ) Acquisition adjustment — (6,278 ) — Revenue recognized 1 (118,317 ) (40,045 ) (45,458 ) Additional amounts deferred 1 133,392 54,170 52,278 Balance at end of period $ 61,200 $ 46,125 $ 38,278 1 Amounts include total revenue deferred and recognized during each respective period.
Schedule of Revenue Remaining Performance Obligation	The remaining performance obligations consisted of the following: (in thousands) September 30, December 31, Current $ 128,653 $ 114,284 Non-current 78,900 58,250 Total $ 207,553 $ 172,534	The remaining performance obligations consisted of the following (in thousands): Successor Company December 31, December 31, Current (1) $ 114,284 $ 82,291 Noncurrent (1) 58,250 40,475 Total $ 172,534 $ 122,766 (1) The above table has been corrected for certain errors. Previously reported current, noncurrent and total amounts were $121,623, $51,368, and $172,991 respectively for 2020 and $90,237, $32,957, and $123,194 respectively for 2019.

Accounts Receivable (Tables)

Accounts Receivable (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Accounts Receivable, after Allowance for Credit Loss, Current [Abstract]
Schedule of Accounts Receivable	Accounts receivable consisted of the following: (in thousands) September 30, December 31, Accounts receivable $ 28,243 $ 33,635 Unbilled receivable 496 329 28,739 33,964 Less: allowance for doubtful accounts (853 ) (856 ) Accounts receivable, net $ 27,886 $ 33,108	Accounts receivable consisted of the following (in thousands): Successor Company December 31, December 31, Accounts receivable $ 33,635 $ 25,220 Unbilled receivable 329 251 $ 33,964 $ 25,471 Less: allowance for doubtful accounts (856 ) (450 ) Accounts receivable, net $ 33,108 $ 25,021

Property and Equipment (Tables)

Property and Equipment (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Schedule of Property Plant and Equipment	Property and equipment consisted of the following: (in thousands) September 30, December 31, Computers and software $ 4,455 $ 3,141 Furniture and equipment 1,580 1,109 Leasehold improvements 2,766 1,781 Construction — 128 8,801 6,159 Less: accumulated depreciation and amortization (4,104 ) (2,911 ) Property and equipment, net $ 4,697 $ 3,248	Property and equipment consisted of the following (in thousands): Successor Company December 31, December 31, Computers and software $ 3,141 $ 2,042 Furniture and equipment 1,109 777 Leasehold improvements 1,781 1,188 Construction in process 128 310 $ 6,159 $ 4,317 Less: accumulated depreciation and amortization (2,911 ) (1,759 ) Property and equipment, net $ 3,248 $ 2,558

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Carrying Amounts of Goodwill and Intangible Assets	The carrying amounts of goodwill and intangible assets, as of September 30, 2021 and December 31, 2020, consist of the following: September 30, 2021 (in thousands) Gross Accumulated Net Carrying Finite-lived intangible assets: Customer relationships $ 370,030 $ (84,159 ) $ 285,871 Developed technologies 51,100 (15,648 ) 35,452 Tradenames 35,500 (4,510 ) 30,990 Database 42,656 (28,246 ) 14,410 Total finite-lived intangible assets 499,286 (132,563 ) 366,723 Goodwill 1,261,444 — 1,261,444 Total goodwill and Intangible assets $ 1,760,730 $ (132,563 ) $ 1,628,167 December 31, 2020 (in thousands) Gross Accumulated Net Carrying Finite-lived intangible assets: Customer relationships $ 370,030 $ (58,097 ) $ 311,933 Developed technologies 51,100 (10,218 ) 40,882 Tradenames 35,500 (2,952 ) 32,548 Database 42,656 (17,782 ) 24,874 Total finite-lived intangible assets 499,286 (89,049 ) 410,237 Goodwill 1,261,444 — 1,261,444 Total goodwill and Intangible assets $ 1,760,730 $ (89,049 ) $ 1,671,681	The carrying amounts of goodwill and intangible assets, as of December 31, 2020 and 2019, consist of the following (in thousands): December 31, 2020 (Successor) Gross Carrying Accumulated Net Carrying Finite-lived intangible assets: Customer relationships $ 370,030 $ (58,097 ) $ 311,933 Developed technologies 51,100 (10,218 ) 40,882 Tradenames 35,500 (2,952 ) 32,548 Data 42,656 (17,782 ) 24,874 Total finite-lived intangible assets 499,286 (89,049 ) 410,237 Goodwill 1,261,444 — 1,261,444 Total goodwill and Intangible assets $ 1,760,730 $ (89,049 ) $ 1,671,681 December 31, 2019 (Successor) Gross Carrying Accumulated Net Carrying Finite-lived intangible assets: Customer relationships $ 358,130 $ (21,075 ) $ 337,055 Developed technologies 48,500 (3,206 ) 45,294 Tradenames 34,100 (928 ) 33,172 Data 36,268 (5,408 ) 30,860 Total finite-lived intangible assets 476,998 (30,617 ) 446,381 Goodwill 1,233,173 — 1,233,173 Total goodwill and Intangible assets $ 1,710,171 $ (30,617 ) $ 1,679,554
Schedule of Estimated Intangible Amortization Expense		Estimated total intangible amortization expense during the next five years and thereafter is as follows (in thousands): 2021 $ 58,143 2022 53,653 2023 45,709 2024 42,485 2025 38,296 Thereafter 171,951 Total $ 410,237
Schedule of Changes in Carrying Amount of Goodwill		The changes in the carrying amount of goodwill for the year ended December 31, 2020 (Successor) and the periods from July 16, 2019 to December 31, 2019 (Successor) and January 1, 2019 through July 15, 2019 (Predecessor) were as follows (in thousands): Balance at January 1, 2019 (Predecessor) $ 63,623 HIMSS acquisition (Note 3) 19,145 Balance at July 15, 2019 (Predecessor) 82,768 Definitive Holdco Acquisition (Note 3) $ 1,144,494 Balance at July 16, 2019 (Successor) $ 1,227,262 HSE acquisition (Note 3) 5,911 Balance at December 31, 2019 (Successor) 1,233,173 Monocl acquisition (Note 3) 28,271 Balance at December 31, 2020 (Successor) $ 1,261,444

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Payables and Accruals [Abstract]
Schedule of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consisted of the following: (in thousands) September 30, 2021 December 31, 2020 Payroll and payroll-related $ 7,246 $ 7,792 Accrued interest 233 5,365 Contingent consideration, current 6,905 1,500 Sales taxes 1,146 649 Deferred rent 112 583 Other 3,654 1,432 Accrued expenses and other current liabilities $ 19,296 $ 17,321	Accrued expenses and other current liabilities consisted of the following (in thousands): Successor Company December 31, 2020 December 31, 2019 Payroll and payroll-related $ 7,792 $ 3,879 Accrued interest 5,365 4,215 Contingent consideration, current 1,500 — Sales taxes 649 1,916 Deferred rent 583 17 Other 1,432 321 Accrued expenses and other current liabilities $ 17,321 $ 10,348

Stockholders' Equity and Memb_2

Stockholders' Equity and Members' Equity (Tables)	9 Months Ended
	Sep. 30, 2021
Stockholders Equity And Members Deficit [Abstract]
Schedule Of Common Stock Units Authorized Issued And Outstanding	The table below provides a summary of the number of Class A and Class B units authorized, issued and outstanding as of December 31, 2020, respectively. December 31, 2020 Class A units: Authorized, issued and outstanding Class A units 130,245,990 Class B units: Authorized Class B units 8,088,877 Issued Class B units 3,720,063 Outstanding Class B units (Vested Class B units) 474,920

Equity-based Compensation (Tabl

Equity-based Compensation (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Summary of Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	Significant assumptions used to estimate the fair value of units were as follows, which were the same between service-based and performance-based shares: September 15, 2021 December 31, 2020 Expected option term 0.30 — 5.5 years Risk-free rate of return 0.01% — 1.73% Applied volatility 30% 35%	Significant assumptions used to estimate the fair value of units were as follows, which were the same between service-based and performance-based shares: Successor Company Year ended Period from Expected option term 5.5 years 5.5 years Risk-free rate of return 1.73 % 1.73 % Applied volatility 35 % 35 %
Schedule of allocation of share based compensation costs by plan	A summary of the expense by line item in the consolidated statements of operations for the nine months ended September 30, 2021 and 2020, respectively, is provided in the following table. Nine Months Ended (in thousands) 2021 2020 Cost of revenue $ 79 $ 46 Sales and marketing 567 380 Product development 341 267 General and administrative 3,351 637 Total compensation expense $ 4,338 $ 1,330	The Company recorded total unit-based compensation of $1.7 million for the year ended December 31, 2020 (Successor) and $0.7 million and $5.8 million for the periods from July 16, 2019 through December 31, 2019 (Successor) and from January 1, 2019 through July 15, 2019 (Predecessor), respectively, as follows in the table below (in thousands): Successor Company Predecessor Year ended Period From Period From Time-based: 2015 plan $ — $ — $ 5,807 2019 plan 1,747 744 — Total time-based 1,747 744 5,807 Performance based: 2015 plan — — — 2019 plan — — — Total performance-based — — — Total compensation expense $ 1,747 $ 744 $ 5,807 Equity-based compensation expense is allocated to all departments in the accompanying consolidated statements of income (loss) based on the recipients of the compensation. A summary of the expense by line item in the consolidated statements of income (loss) for the year ended December 31, 2020 (Successor) and the periods from July 16, 2019 to December 31, 2019 (Successor), and from January 1, 2019 to July 15, 2019 (Predecessor) is provided in the following table (in thousands). Successor Company Predecessor Year ended Period From Period From Cost of revenue $ 62 $ 28 $ 256 Sales and Marketing 473 213 4,252 Product Development 356 126 665 General and administrative 856 377 634 Total compensation expense $ 1,747 $ 744 $ 5,807
Schedule Of Unvested Restricted Stock Options	The following table summarizes the Company’s unvested time-based and performance-based RSU activity for the nine months ended September 30, 2021. Time-Based Performance-Based Restricted Stock Units Weighted Average Grant Date Fair Value Restricted Stock Units Weighted Average Grant Date Fair Value Unvested at beginning of period — $ — — $ — Granted 1,300,328 $ 27.00 164,353 $ 27.00 Vested — $ — — $ — Forfeited (2,656 ) $ 27.00 — $ — Unvested at end of period 1,297,672 $ 27.00 164,353 $ 27.00
Time Based Restricted Stock Units [Member]
Schedule Of Unvested Restricted Stock Options	The following table summarizes the Company’s unvested time-based and performance-based unit activity from January 1, 2021 through September 30, 2021. Time-Based Performance-Based Non-Vested Weighted Non-Vested Weighted Non-vested 1,404,720 $ 3.65 1,840,423 $ 2.35 Granted 1,477,323 1.41 1,177,308 0.41 Vested (437,731 ) 3.64 — — Forfeited (13,770 ) 3.65 (18,361 ) 2.35 Non-vested 2,430,542 $ 2.29 2,999,370 $ 1.59 Effect of Reorganization Transactions and IPO (1,165,679 ) 2.08 (1,318,171 ) 1.39 Performance-based units exchanged for time-based units 1,681,199 1.74 (1,681,199 ) 1.74 Vested (74,049 ) 2.75 — — Forfeited (72,149 ) 2.78 — — Non-vested 2,799,864 $ 2.02 — $ —
2019 Incentive Equity Pool [Member]
Summary of Nonvested Restricted Stock Shares Activity		The following table summarizes the Company’s unvested time-based and performance-based unit activity under the 2019 plan for the year ended December 31, 2020 (Successor) and the periods from July 16, 2019 and December 31, 2019 (Successor) and January 1, 2019 to July 15, 2019 (Predecessor): Time-based Performance-based 2019 Plan Non-Vested Weighted Non-Vested Weighted Non-vested — $ — — $ — Granted — — — — Vested — — — — Non-vested — $ — — $ — Granted 1,899,682 3.65 1,899,682 2.35 Vested — — — — Forfeited — — — — Non-vested 1,899,682 $ 3.65 1,899,682 $ 2.35 Granted 97,611 3.65 97,611 2.35 Vested (474,920 ) 3.65 — — Forfeited (117,653 ) 3.65 (156,870 ) 2.35 Non-vested 1,404,720 $ 3.65 1,840,423 $ 2.35
2015 Incentive Equity Pool [Member]
Summary of Nonvested Restricted Stock Shares Activity		The following table summarizes the 2015 Plan activity for the periods from January 1, 2019 through July 15, 2019 (Predecessor), and July 16, 2019 through December 31, 2019 (Successor). 2015 Plan Non-Vested Weighted Non-vested 131,545 $ 9.00 Granted 48,592 98.75 Vested (180,137 ) 33.21 Forfeited — — Non-vested — $ — Granted — — Vested — — Forfeited — — Non-vested — $ —

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Schedule of Minimum Future Rental Payments	Minimum future rental payments are expected to be as follows for each of the years ending December 31 (in thousands): 2021 $ 3,035 2022 2,673 2023 2,043 2024 2,338 2025 2,193 Thereafter 4,790 $ 17,072
Schedule of Estimated Annual Minimum Purchase Commitments	The estimated annual minimum purchase commitments under those agreements were as follows for each of the years ending December 31 (in thousands): 2021 $ 5,396 2022 5,257 2023 5,098 2024 3,925 2025 2,370 Thereafter — $ 22,046

Long-term debt (Tables)

Long-term debt (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Debt Disclosure [Abstract]
Schedule of Long-term Debt	Long-term debt consisted of the following as of September 30, 2021 and December 31, 2020, respectively: September 30, 2021 (in thousands) Principal Unamortized debt Total debt, 2021 Term Loan $ 275,000 $ (2,737 ) $ 272,263 Less: current portion of long-term debt 6,875 Long-term debt $ 265,388 December 31, 2020 (in thousands) Principal Unamortized debt Total debt, 2019 Term Loan $ 444,375 $ (10,865 ) $ 433,510 Paid in kind interest on 2019 Term Loan 10,412 — 10,412 2019 Delayed Draw Term Loan 17,955 — 17,955 Total debt $ 472,742 $ (10,865 ) $ 461,877 Less: current portion of long-term debt 4,680 Long-term debt $ 457,197	Long-term debt consisted of the following as of December 31, 2020 and 2019, respectively (in thousands): December 31, 2020 (Successor) Principal Unamortized debt Total debt, net 2019 Term Note $ 444,375 $ (10,865 ) $ 433,510 Paid in kind interest on 2019 Term Note 10,412 10,412 2019 Delayed Draw Term Note 17,955 17,955 Total debt $ 472,742 $ (10,865 ) 461,877 Less: current portion of long-term debt 4,680 Long-term debt $ 457,197 December 31, 2019 (Successor) Principal Unamortized debt Total debt, net 2019 Term Note $ 448,875 $ (12,567 ) $ 436,308 Paid in kind interest on 2019 Term Note 3,041 3,041 Total debt $ 451,916 $ (12,567 ) 439,349 Less: current portion of long-term debt 4,500 Long-term debt $ 434,849
Schedule of Future principal payments		Future principal payments as of December 31, 2020 are as follows (in thousands): 2021 $ 4,680 2022 4,680 2023 4,680 2024 4,680 2025 4,680 Thereafter 449,342 $ 472,742

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Schedule of Reconciliation of Earnout Liabilities Measeured at Fair Value	The table below presents a reconciliation of earnout liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3): (in thousands) September 30, December 31, Balance at beginning of period $ 5,236 $ — Additions — 2,600 Net change in fair value and other adjustments 3,169 2,636 Payments (1,500 ) — Balance at end of period $ 6,905 $ 5,236	The table below presents a reconciliation of earnout liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) (in thousands): Successor Company Predecessor Company Year ended Period from Period from Balance at beginning of period $ — $ — $ — Additions 2,600 — — Net change in fair value and other adjustments 2,636 — — Payments — — — Balance at end of period $ 5,236 $ — $ —
Schedule of Significant Unobservable Inputs Used Recurring Level 3 Fair Value Measurements	The valuation techniques and significant unobservable inputs used in recurring Level 3 fair value measurements were as follows as of September 30, 2021 and December 31, 2020: (in thousands) Fair Value Valuation Technique Unobservable Inputs Discount Rate Earn-out $ 6,905 Income Approach (Real Option Method) Discount rate 2.38 %	The valuation techniques and significant unobservable inputs used in recurring Level 3 fair value measurements were as follows as of December 31, 2020: Fair Value Valuation Technique Unobservable Inputs Discount Rate Earn-out $ 5,236 Income Approach (Real Option Method) Discount rate 6.5 %

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Provision or Benefit	The components of the income tax provision are as follows (in thousands): Successor Company Predecessor Year ended Period from Period from Current tax provision: Federal $ 10 $ — $ — State 1 — — Foreign — — — Total current tax provision $ 11 $ — $ — Deferred tax provision: Federal $ 58 $ — $ — State (7 ) — 49 Foreign — — — Total deferred tax provision 51 — 49 Total provision $ 62 $ — $ 49
Schedule of Components of Deferred Tax Assets and Liabilities	Deferred taxes are recognized for temporary differences between the basis of assets and liabilities for financial statement and income tax purposes. The significant components of the deferred tax assets are comprised of the following (in thousands): Successor Company December 31, 2020 December 31, 2019 Deferred tax assets: Foreign, U.S. and state net operating loss carryforwards $ 1,517 $ 212 Accrued Expenses 12 — Unrealized foreign exchange losses 62 — Subtotal 1,591 212 Less valuation allowance (1,430 ) — Total deferred tax assets 161 212 Net deferred tax assets $ 161 $ 212
Schedule of Reconciliation of Income Tax Expense	A reconciliation of income tax expense computed at the statutory federal income tax rate to income taxes as reflected in the financial statements is as follows: Successor Company Predecessor Year ended Period from Period from Federal income tax expense at statutory rate 21.00 % 21.00 % 0.00 % State income tax, net of federal benefit (0.14 ) 0.04 0.00 Permanent differences (0.98 ) (2.73 ) 0.00 Research and development credit 0.00 0.00 0.00 Foreign rate differential (0.01 ) 0.00 0.00 Change in valuation allowance 0.60 0.00 0.00 Provision to return adjustments 0.46 0.00 0.00 Other 6.50 (0.04 ) 0.37 Pass through income not subject to tax (27.55 ) (18.27 ) 0.01 Effective income tax rate (0.12 %) 0.00 % 0.38 %

Loss Per Share (Tables)

Loss Per Share (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Earnings Per Share [Abstract]
Schedule of Reconciliation of Earnings Per Share Basic and Diluted	The following table sets forth reconciliations of the numerators and denominators used to compute basic and diluted net loss per share of Class A Common Stock for the nine-months ended September 30, 2021. The basic and diluted earnings per share for the nine-months ended September 30, 2021 reflects only the period from September 15, 2021 to September 30, 2021, which represents the period wherein the Company had outstanding Class A Common Stock. (in thousands) Nine Months Ended 2021 Numerator: Net loss $ (46,493 ) Less: Net loss attributable to Definitive OpCo before Reorganization Transactions (33,343 ) Less: Net loss attributable to noncontrolling interests (5,172 ) Net loss attributable to Definitive Healthcare Corp. $ (7,978 )
Schedule Of Computation Of Earnings Per Share Basic And Diluted	The following table sets forth the computation of basic and diluted net loss per share of Class A Common Stock (per share amounts unaudited): (in thousands, except number of shares and per share amounts) Nine Months Ended 2021 Basic net loss per share attributable to common stockholders Numerator: Allocation of net loss attributable to Definitive Healthcare Corp. $ (7,978 ) Weighted average number of shares of Class A outstanding 88,263,333 Net loss per share, basic and diluted $ (0.09 )	The following table presents the calculation of basic and diluted net income/(loss) per unit (“EPU”) for the Company’s common units: Successor Company Year Ended Period from Net loss $ (51,157 ) $ (49,266 ) Weighted-average units used to compute basic and diluted net loss per unit 127,682,376 126,794,329 Net loss per unit, basic and diluted $ (0.40 ) $ (0.39 )
Schedule of Potentially Dilutive Securities Excluded From The Computation Of Diluted Net Loss Per Share	The following table presents potentially dilutive securities excluded from the computation of diluted net loss per share for the period presented because their effect would have been anti-dilutive: Nine Months Ended Definitive OpCo Units 57,192,893

Segment and Geographic Data (Ta

Segment and Geographic Data (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Segment Reporting [Abstract]
Summary Of Revenues By Geographic Area Presented Based Upon The Location Of The Customer	Revenues by geographic area presented based upon the location of the customer are as follows: For the Nine Months Ended September 30, (in thousands) 2021 2020 United States $ 114,339 $ 84,659 Rest of world 5,502 — Total revenues $ 119,841 $ 84,659	Revenues by geographic area presented based upon the location of the customer are as follows (in thousands): Successor Company Predecessor Year Ended Period from Period from United States $ 117,755 $ 40,045 $ 45,458 Rest of world 562 — — Total revenues $ 118,317 $ 40,045 $ 45,458
Summary of Long-lived Assets by Geographical Region are Based on the Location of the Legal Entity that Owns the Assets	Long-lived assets by geographic area presented based upon the location of the assets are as follows: (in thousands) September 30, 2021 December 31, 2020 United States $ 4,311 $ 3,120 Rest of world 386 128 Total long-lived assets $ 4,697 $ 3,248	Long-lived assets by geographical region are based on the location of the legal entity that owns the assets. Long-lived assets by geographic area presented based upon the location of the assets are as follows (in thousands): Successor Company December 31, 2020 December 31, 2019 United States $ 3,120 $ 2,558 Rest of world 128 — Total long-lived assets $ 3,248 $ 2,558

Description of Business - Addit

Description of Business - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	Sep. 17, 2021	Sep. 30, 2021	Jun. 30, 2021
Issue of limited liability company interests	1,169,378
IPO [Member]
Proceeds from issuance of common stock	$ 452.8
Issue of limited liability company interests	14,222,222
Common Class A [Member]
Stock issued during period, shares		17,888,888
Proceeds from issuance of common stock			$ 5.8
Stock repurchased during period, shares		2,497,288
Common Class A [Member] | IPO [Member]
Stock issued during period, shares	17,888,888
Shares issued, price per share	$ 27
Stock repurchased during period, shares	2,497,288

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jul. 15, 2019	Dec. 31, 2020	Dec. 31, 2019	Sep. 30, 2021	Jul. 16, 2019	Jan. 01, 2019	Dec. 31, 2018
Significant Accounting Policies [Line Items]
Allowance for doubtful accounts		$ 856	$ 450	$ 853
Current portion of deferred contract costs	$ 1,906	2,947	769	5,359		$ 1,346
Deferred contract costs, net of current portion	3,829	5,952	2,116	9,388		2,973
Advertising expense	200	600	200
Unamortized debt issuance costs		10,900	12,600	3,500
Deferred costs		0
Uncertain tax positions		0	0
Increase (decrease) in partners capital due to adoption of accounting standards	5,415
Deferred revenue	38,278	61,200	46,125	$ 70,179	$ 32,000	31,458	$ 32,187
Unbilled revenues		$ 1,100
Cumulative Effect, Period of Adoption, Adjustment [Member]
Significant Accounting Policies [Line Items]
Current portion of deferred contract costs			(769)			1,346
Deferred contract costs, net of current portion			(2,116)			$ 2,973
Increase (decrease) in partners capital due to adoption of accounting standards	$ 5,400
Furniture and equipment [Member]
Significant Accounting Policies [Line Items]
Property plant and equipment, estimated useful life		5 years
Computers and software [Member]
Significant Accounting Policies [Line Items]
Property plant and equipment, estimated useful life		3 years
Property, Plant and Equipment [Member]
Significant Accounting Policies [Line Items]
Software development costs capitalized		$ 100	0		$ 0
Software and Software Development Costs [Member]
Significant Accounting Policies [Line Items]
Capitalized contract costs, amortization period		3 years
Leasehold Improvements [Member]
Significant Accounting Policies [Line Items]
Property plant and equipment lease term		Lesser of the asset life or lease term
Current Portion Of Deferred Contract Costs [Member]
Significant Accounting Policies [Line Items]
Capitalized contract costs		$ 8,900	$ 2,900
Deferred revenue		$ 4,300
Minimum [Member]
Significant Accounting Policies [Line Items]
Capitalized contract costs, amortization period		2 years
Minimum [Member] | Customer relationships [Member]
Significant Accounting Policies [Line Items]
Finite lived intangible assets		14 years
Minimum [Member] | Technology-Based Intangible Assets [Member]
Significant Accounting Policies [Line Items]
Finite lived intangible assets		7 years
Minimum [Member] | Trademarks [Member]
Significant Accounting Policies [Line Items]
Finite lived intangible assets		17 years
Minimum [Member] | Data [Member]
Significant Accounting Policies [Line Items]
Finite lived intangible assets		1 year
Maximum [Member]
Significant Accounting Policies [Line Items]
Capitalized contract costs, amortization period		4 years
Maximum [Member] | Customer relationships [Member]
Significant Accounting Policies [Line Items]
Finite lived intangible assets		15 years
Maximum [Member] | Technology-Based Intangible Assets [Member]
Significant Accounting Policies [Line Items]
Finite lived intangible assets		8 years
Maximum [Member] | Trademarks [Member]
Significant Accounting Policies [Line Items]
Finite lived intangible assets		19 years
Maximum [Member] | Data [Member]
Significant Accounting Policies [Line Items]
Finite lived intangible assets		4 years
Customer Concentration Risk [Member] | Revenue Benchmark [Member]
Significant Accounting Policies [Line Items]
Concentration risk percentage		10.00%	10.00%

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Schedule Of Changes On Balance Sheet And Income Statement Due To The Adoption Of New Accounting pronouncements (Detail) - USD ($)	6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2019	Jul. 15, 2019	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	May 24, 2021	Jan. 01, 2019
Consolidated Balance Sheet:
Accounts receivable, net	$ 25,021,000		$ 27,886,000		$ 33,108,000		$ 14,932,000
Current portion of deferred contract costs	769,000	$ 1,906,000	5,359,000		2,947,000		1,346,000
Total current assets	36,107,000		226,639,000		63,845,000	$ 100	35,176,000
Deferred contract costs, net of current portion	2,116,000	3,829,000	9,388,000		5,952,000		2,973,000
Total assets	1,721,154,000		1,869,799,000		1,745,359,000		87,061,000
Current portion of deferred revenue	45,977,000		69,811,000		61,060,000		32,187,000
Total current liabilities	69,917,000		103,037,000		88,723,000		36,676,000
Total liabilities	504,914,000		586,715,000		549,796,000		36,676,000
Members' capital	1,216,240,000						50,385,000
Total liabilities and members' capital	1,721,154,000		1,869,799,000		1,745,359,000		87,061,000
Income Statement [Abstract]
Revenue	40,045,000	45,458,000	119,841,000	$ 84,659,000	118,317,000
Total cost of revenue	13,282,000	5,328,000
Gross profit	26,763,000	40,130,000	90,050,000	62,505,000	87,849,000
Sales and marketing	10,814,000	16,039,000	39,003,000	23,542,000	34,332,000
Total operating expenses	57,825,000	27,097,000	102,857,000	69,998,000	102,294,000
Income (loss) from operations	(31,062,000)	13,033,000	(12,807,000)	(7,493,000)	(14,445,000)
Total other expense, net	(18,204,000)	(165,000)	(33,686,000)	(27,802,000)	(36,712,000)
Net income (loss)	(49,266,000)	12,868,000	$ (46,493,000)	$ (35,295,000)	$ (51,157,000)
Adjustments
Consolidated Balance Sheet:
Accounts receivable, net	(250,000)						367,000
Current portion of deferred contract costs	(769,000)						1,346,000
Total current assets	(1,019,000)						1,713,000
Deferred contract costs, net of current portion	(2,116,000)						2,973,000
Total assets	(3,135,000)						4,686,000
Current portion of deferred revenue	990,000						(729,000)
Total current liabilities	990,000						(729,000)
Total liabilities	990,000						(729,000)
Members' capital	(4,125,000)						5,415,000
Total liabilities and members' capital	(3,135,000)						4,686,000
Income Statement [Abstract]
Revenue	(66,000)	(79,000)
Total cost of revenue	0	0
Gross profit	(66,000)	(79,000)
Sales and marketing	2,885,000	1,416,000
Total operating expenses	2,885,000	1,416,000
Income (loss) from operations	(2,951,000)	(1,495,000)
Total other expense, net	0	0
Net income (loss)	(2,951,000)	(1,495,000)
As Adjusted
Consolidated Balance Sheet:
Accounts receivable, net	24,771,000						15,299,000
Current portion of deferred contract costs							1,346,000
Total current assets	35,088,000						36,889,000
Deferred contract costs, net of current portion							2,973,000
Total assets	1,718,019,000						91,747,000
Current portion of deferred revenue	46,967,000						31,458,000
Total current liabilities	70,907,000						35,947,000
Total liabilities	505,904,000						35,947,000
Members' capital	1,212,115,000						55,800,000
Total liabilities and members' capital	1,718,019,000						$ 91,747,000
Income Statement [Abstract]
Revenue	39,979,000	45,379,000
Total cost of revenue	13,282,000	5,328,000
Gross profit	26,697,000	40,051,000
Sales and marketing	13,699,000	17,455,000
Total operating expenses	60,710,000	28,513,000
Income (loss) from operations	(34,013,000)	11,538,000
Total other expense, net	(18,204,000)	(165,000)
Net income (loss)	$ (52,217,000)	$ 11,373,000

Business Combinations - Additio

Business Combinations - Additional Information (Detail) - USD ($)

Oct. 27, 2020

Dec. 02, 2019

Jul. 16, 2019

Jan. 15, 2019

Jul. 31, 2020

Dec. 31, 2019

Jul. 15, 2019

Sep. 30, 2021

Sep. 30, 2020

Dec. 31, 2020

Dec. 31, 2019

Dec. 31, 2021

Dec. 31, 2017

Business Acquisition [Line Items]

Business Combination, rollover equity

$ 6,400,000

Fair value of the contingent consideration

$ 6,900,000

5,200,000

Business Combination, Recognized Identifiable Assets and Liabilities, Goodwill

$ 1,227,262,000

$ 1,233,173,000

$ 82,768,000

1,261,444,000

1,261,444,000

$ 1,233,173,000

$ 63,623,000

Business Combination, deferred revenue

$ 2,900,000

32,000,000

Business Combination, contingent consideration liability

2,600,000

Acquisition expenses

400,000

400,000

Revenue

40,045,000

45,458,000

119,841,000

$ 84,659,000

118,317,000

Net loss

(49,266,000)

12,868,000

(46,493,000)

(35,295,000)

(51,157,000)

Amortization of intangible assets

30,600,000

2,000,000

43,500,000

43,500,000

Interest expense

18,204,000

165,000

23,956,000

27,802,000

36,490,000

Debt current

4,500,000

6,875,000

4,680,000

4,500,000

Repayments debt financing

432,400,000

25,000,000

Consideration paid

1,122,400,000

$ 6,900,000

Revolving Credit Facility [Member]

Business Acquisition [Line Items]

Long-term Line of Credit

25,000,000

2019 Term Loan

Business Acquisition [Line Items]

Debt current

450,000,000

Long-term Line of Credit

454,800,000

Interest expense

$ 1,500,000

1,500,000

2019 Delayed Draw Term Loan

Business Acquisition [Line Items]

Debt current

$ 100,000,000

2019 Delayed Draw Term Loan | Revolving Credit Facility [Member]

Business Acquisition [Line Items]

Long-term Line of Credit

$ 0

AIDH Finance Sub capital [Member]

Business Acquisition [Line Items]

Percentage of financing agreements, collateralized

100.00%

AIDH Buyer and Definitive Holdco [Member]

Business Acquisition [Line Items]

Total estimated consideration

$ 1,267,300,000

Business Combination, cash consideration

697,000,000

Business Combination, rollover equity

$ 570,300,000

Percentage of financing agreements, collateralized

100.00%

AIDH Buyer [Member]

Business Acquisition [Line Items]

Business Combination, Recognized Identifiable Assets and Liabilities, Goodwill

$ 1,144,500,000

Finite-Lived Intangible Assets [Member]

Business Acquisition [Line Items]

Business Combination, Recognized Identifiable Assets and Liabilities, Intangible asset

456,300,000

Customer relationships [Member]

Business Acquisition [Line Items]

Business Combination, Recognized Identifiable Assets and Liabilities, Intangible asset

340,800,000

Data [Member]

Business Acquisition [Line Items]

Business Combination, Recognized Identifiable Assets and Liabilities, Intangible asset

34,300,000

Technology-Based Intangible Assets [Member]

Business Acquisition [Line Items]

Business Combination, Recognized Identifiable Assets and Liabilities, Intangible asset

48,500,000

Trademarks [Member]

Business Acquisition [Line Items]

Business Combination, Recognized Identifiable Assets and Liabilities, Intangible asset

32,700,000

Minimum [Member] | Customer relationships [Member]

Business Acquisition [Line Items]

Finite-lived Intangible Assets, estimated remaining useful life

14 years

Minimum [Member] | Data [Member]

Business Acquisition [Line Items]

Finite-lived Intangible Assets, estimated remaining useful life

1 year

Minimum [Member] | Technology-Based Intangible Assets [Member]

Business Acquisition [Line Items]

Finite-lived Intangible Assets, estimated remaining useful life

7 years

Minimum [Member] | Trademarks [Member]

Business Acquisition [Line Items]

Finite-lived Intangible Assets, estimated remaining useful life

17 years

Maximum [Member] | Customer relationships [Member]

Business Acquisition [Line Items]

Finite-lived Intangible Assets, estimated remaining useful life

15 years

Maximum [Member] | Data [Member]

Business Acquisition [Line Items]

Finite-lived Intangible Assets, estimated remaining useful life

4 years

Maximum [Member] | Technology-Based Intangible Assets [Member]

Business Acquisition [Line Items]

Finite-lived Intangible Assets, estimated remaining useful life

8 years

Maximum [Member] | Trademarks [Member]

Business Acquisition [Line Items]

Finite-lived Intangible Assets, estimated remaining useful life

19 years

Monocl Holding Company

Business Acquisition [Line Items]

Total estimated consideration

46,346,000

$ 46,346,000

Business Combination, cash consideration

18,307,000

18,307,000

Business Combination, rollover equity

25,439,000

25,439,000

Business Combination, contingent consideration

2,600,000

2,600,000

Business Combination,estimated fair value

2,600,000

Business Combination, Recognized Identifiable Assets and Liabilities, Goodwill

28,271,000

28,271,000

Business Combination, Recognized Identifiable Assets and Liabilities, Intangible asset

18,900,000

18,900,000

Business Combination, deferred revenue

(2,884,000)

(2,884,000)

Acquisition expenses

400,000

Revenue

1,200,000

Net loss

1,600,000

Amortization of intangible assets

800,000

1,200,000

Interest expense

1,000,000

1,200,000

Business Combination, Recognized Identifiable Assets and Liabilities, accounts receivable

788,000

788,000

Business Combination, Recognized Identifiable Assets and Liabilities, Accounts Payable

(2,137,000)

$ (2,137,000)

Adjustments to amortization expense

600,000

Interest expense

$ 800,000

Monocl Holding Company | Revolving Credit Facility [Member]

Business Acquisition [Line Items]

Business Combination, rollover equity

25,400,000

Business Combination, contingent consideration

15,000,000

Monocl Holding Company | Customer relationships [Member]

Business Acquisition [Line Items]

Business Combination, Recognized Identifiable Assets and Liabilities, Intangible asset

11,900,000

Finite-lived Intangible Assets, fair value

$ 11,900,000

Finite-lived Intangible Assets, estimated remaining useful life

14 years

Finite-lived Intangible Assets, weighted average amortization period

15 years

Monocl Holding Company | Data [Member]

Business Acquisition [Line Items]

Business Combination, Recognized Identifiable Assets and Liabilities, Intangible asset

$ 3,000,000

Finite-lived Intangible Assets, fair value

$ 3,000,000

Finite-lived Intangible Assets, estimated remaining useful life

3 years

Finite-lived Intangible Assets, weighted average amortization period

3 years

Monocl Holding Company | Technology-Based Intangible Assets [Member]

Business Acquisition [Line Items]

Business Combination, Recognized Identifiable Assets and Liabilities, Intangible asset

$ 2,600,000

Finite-lived Intangible Assets, fair value

$ 2,600,000

Finite-lived Intangible Assets, estimated remaining useful life

8 years

Finite-lived Intangible Assets, weighted average amortization period

8 years

Monocl Holding Company | Trademarks [Member]

Business Acquisition [Line Items]

Business Combination, Recognized Identifiable Assets and Liabilities, Intangible asset

$ 1,400,000

Finite-lived Intangible Assets, fair value

$ 1,400,000

Finite-lived Intangible Assets, estimated remaining useful life

19 years

Finite-lived Intangible Assets, weighted average amortization period

17 years

Monocl Holding Company | Minimum [Member]

Business Acquisition [Line Items]

Total estimated consideration

$ 46,300,000

Monocl Holding Company | Maximum [Member]

Business Acquisition [Line Items]

Total estimated consideration

$ 60,000,000

Definitive Holdco [Member]

Business Acquisition [Line Items]

Total estimated consideration

1,699,600,000

$ 1,699,612,000

Business Combination, cash consideration

1,129,300,000

1,129,346,000

Business Combination, rollover equity

570,300,000

570,266,000

Business Combination, Recognized Identifiable Assets and Liabilities, Goodwill

1,227,261,000

82,767,000

Business Combination, Recognized Identifiable Assets and Liabilities, Intangible asset

475,400,000

19,108,000

Business Combination, deferred revenue

32,000,000

38,278,000

Acquisition expenses

$ 4,004,000

Revenue

40,000,000

45,500,000

116,900,000

Net loss

$ 49,200,000

12,900,000

49,900,000

Amortization of intangible assets

33,400,000

Interest expense

21,000,000

Business Acquisition, Percentage of Voting Interests Acquired

100.00%

Long-term Line of Credit

$ 436,359,000

Fair value adjustments for deferred revenue

$ 1,400,000

Business Combination, Recognized Identifiable Assets and Liabilities, accounts receivable

12,747,000

12,747,000

Business Combination, Recognized Identifiable Assets and Liabilities, Accounts Payable

(15,200,000)

$ (5,477,000)

Definitive Holdco [Member] | Customer relationships [Member]

Business Acquisition [Line Items]

Finite-lived Intangible Assets, fair value

$ 358,000

Finite-lived Intangible Assets, estimated remaining useful life

15 years

Definitive Holdco [Member] | Data [Member]

Business Acquisition [Line Items]

Finite-lived Intangible Assets, fair value

$ 34,800,000

Finite-lived Intangible Assets, estimated remaining useful life

3 years

Definitive Holdco [Member] | Technology-Based Intangible Assets [Member]

Business Acquisition [Line Items]

Finite-lived Intangible Assets, fair value

$ 48,500,000

Finite-lived Intangible Assets, estimated remaining useful life

10 years

Definitive Holdco [Member] | Trademarks [Member]

Business Acquisition [Line Items]

Finite-lived Intangible Assets, fair value

$ 34,100,000

Finite-lived Intangible Assets, estimated remaining useful life

22 years

HIMSS

Business Acquisition [Line Items]

Total estimated consideration

$ 29,800,000

Business Combination, Recognized Identifiable Assets and Liabilities, Goodwill

19,100,000

Business Combination, Recognized Identifiable Assets and Liabilities, Intangible asset

11,400,000

Business Combination, deferred revenue

2,000,000

Business Combination, Recognized Identifiable Assets and Liabilities, accounts receivable

$ 1,300,000

HSE

Business Acquisition [Line Items]

Total estimated consideration

$ 6,800,000

Business Combination, cash consideration

2,800,000

Business Combination, rollover equity

4,000,000

Business Combination, Recognized Identifiable Assets and Liabilities, Goodwill

5,900,000

Business Combination, Recognized Identifiable Assets and Liabilities, Intangible asset

1,200,000

Business Combination, deferred revenue

$ 300,000

Business Acquisition, Percentage of Voting Interests Acquired

100.00%

Business Combination, Recognized Identifiable Assets and Liabilities, Deferred Tax Assets

$ 200,000

Business Combination, Recognized Identifiable Assets and Liabilities, accounts receivable

100,000

Business Combination, Recognized Identifiable Assets and Liabilities, Accounts Payable

$ 300,000

AIDH [Member] | Advent IX Funds [Member]

Business Acquisition [Line Items]

Business Acquisition, Percentage of Voting Interests Acquired

100.00%

AIDH [Member] | AIDH Holdings [Member]

Business Acquisition [Line Items]

Business Acquisition, Percentage of Voting Interests Acquired

55.00%

AIDH [Member] | Definitive Holdco [Member]

Business Acquisition [Line Items]

Business Acquisition, Percentage of Voting Interests Acquired

45.00%

AIDH [Member] | Definitive Healthcare Corp [Member]

Business Acquisition [Line Items]

Business Acquisition, Percentage of Voting Interests Acquired

100.00%

AIDH [Member] | AIDH Buyer [Member]

Business Acquisition [Line Items]

Business Acquisition, Percentage of Voting Interests Acquired

100.00%

Annual Recurring Revenue [Member] | Minimum [Member]

Business Acquisition [Line Items]

Business Combination, Contingent Consideration, Range of Outcomes, Value, low

0

$ 0

Business Combination, Contingent Consideration, Range of Outcomes, Value, High

5,000,000

10,000,000

Annual Recurring Revenue [Member] | Maximum [Member]

Business Acquisition [Line Items]

Business Combination, Contingent Consideration, Range of Outcomes, Value, low

8,500,000

12,000,000

Business Combination, Contingent Consideration, Range of Outcomes, Value, High

$ 9,500,000

$ 16,000,000

Business Combinations - Schedul

Business Combinations - Schedule of Consideration Transferred in Business Combination (Detail) - USD ($) $ in Thousands	Oct. 27, 2020	Jul. 16, 2019	Dec. 31, 2020
Business Acquisition [Line Items]
Equity issuance			$ 6,400
Monocl Holding Company
Business Acquisition [Line Items]
Cash consideration	$ 18,307		18,307
Equity issuance	25,439		25,439
Contingent consideration	2,600		2,600
Purchase price	$ 46,346		46,346
Definitive Holdco
Business Acquisition [Line Items]
Cash consideration		$ 1,129,300	1,129,346
Equity issuance		570,300	570,266
Purchase price		$ 1,699,600	$ 1,699,612

Business Combinations - Sched_2

Business Combinations - Schedule of Recognized Assets and Libailities Pertaining to Business Combination (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Oct. 27, 2020	Dec. 31, 2019	Jul. 16, 2019	Jul. 15, 2019	Jan. 01, 2019	Dec. 31, 2017
Preliminary allocation:
Deferred revenue			$ 2,900		$ 32,000
Goodwill	$ 1,261,444	$ 1,261,444		$ 1,233,173	1,227,262	$ 82,768		$ 63,623
Members' Capital				1,216,240			$ 50,385
Total liabilities and equity	$ 1,869,799	1,745,359		$ 1,721,154			$ 87,061
Monocl Holding Company
Preliminary allocation:
Cash		2,774	2,774
Accounts receivable		788	788
Prepaid expenses and other current assets		614	614
Property and equipment		20	20
Intangible assets		18,900	18,900
Accounts payable and accrued expenses		(2,137)	(2,137)
Deferred revenue		(2,884)	(2,884)
Total assets acquired and liabilities assumed		18,075	18,075
Goodwill		28,271	28,271
Purchase price		$ 46,346	$ 46,346
Definitive Holdco
Preliminary allocation:
Cash					17,058	17,058
Accounts receivable					12,747	12,747
Deferred contract costs						5,735
Prepaid expenses and other current assets					1,705	1,539
Other assets					14,638	49
Property and equipment					2,201	2,201
Intangible assets					475,400	19,108
Total assets					1,751,010	141,204
Accounts payable and accrued expenses					(15,200)	(5,477)
Deferred revenue					32,000	38,278
Goodwill					1,227,261	82,767
Purchase price					(1,699,612)
Term Loan					436,553
Total liabilities					483,753	43,755
Members' Capital					1,267,257	97,449
Total liabilities and equity					1,751,010	141,204
Definitive Holdco | At Carrying Value [Member]
Preliminary allocation:
Cash						17,058
Accounts receivable						12,747
Deferred contract costs						5,735
Prepaid expenses and other current assets						1,539
Other assets						49
Property and equipment						2,201
Intangible assets						19,108
Accounts payable and accrued expenses						(5,477)
Deferred revenue						(38,278)
Total assets acquired and liabilities assumed						14,682
Goodwill						82,767
Definitive Holdco | At Fair Value [Member]
Preliminary allocation:
Deferred contract costs					(5,735)	(5,735)
Prepaid expenses and other current assets					150	150
Intangible assets					456,292	456,292
Total assets						1,595,201
Accounts payable and accrued expenses					(684)	(684)
Deferred revenue					(6,278)	(6,278)
Total assets acquired and liabilities assumed					457,669
Goodwill					1,144,494	1,144,494
Total liabilities						6,962
Members' Capital						1,602,163
Total liabilities and equity						1,595,201
Definitive Holdco | Debt Financing Or Finance Merger [Member]
Preliminary allocation:
Cash					17,058
Accounts receivable					12,747
Prepaid expenses and other current assets					1,689	16
Other assets					49	14,589
Property and equipment					2,201
Intangible assets					475,400
Total assets						14,605
Accounts payable and accrued expenses					(4,793)	(10,407)
Deferred revenue					(32,000)
Total assets acquired and liabilities assumed					472,351
Goodwill					1,227,261
Purchase price					$ 1,699,612
Term Loan						436,553
Total liabilities						446,960
Members' Capital						(432,355)
Total liabilities and equity						$ 14,605

Business Combinations - Sched_3

Business Combinations - Schedule of Proforma Information Related to Business Combination (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Monocl Holding Company
Business Acquisition [Line Items]
Revenue	$ 91,750	$ 122,333	$ 87,157
Net loss	$ (43,763)	$ (58,350)	(97,134)
Definitive Holdco
Business Acquisition [Line Items]
Revenue			84,122
Net loss			$ (92,228)

Business Combinations - Sched_4

Business Combinations - Schedule of Reconciliation of Purchase Price to the Capital Contribution (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Jul. 16, 2019
Business Acquisition [Line Items]
Transaction costs paid from proceeds	$ 400	$ 400
Definitive Holdco [Member]
Business Acquisition [Line Items]
Total purchase price			$ 1,699,612
Transaction costs paid from proceeds			4,004
Less Debt Financing			436,359
Capital Contribution			$ 1,267,257

Revenue - Schedule of Disaggreg

Revenue - Schedule of Disaggregation of Revenue (Detail) - USD ($) $ in Thousands	6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2019	Jul. 15, 2019	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Revenue	$ 40,045	$ 45,458	$ 119,841	$ 84,659	$ 118,317
Platform Subscriptions [Member]
Disaggregation of Revenue [Line Items]
Revenue	39,872	45,244	118,545	83,814	117,080
Professional Services [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 173	$ 214	$ 1,296	$ 845	$ 1,237

Revenue - Schedule of Opening a

Revenue - Schedule of Opening and Closing Balances of Receivables Deferred Contract Costs and Contract Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019	Jul. 16, 2019	Jul. 15, 2019	Jan. 01, 2019	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Accounts receivable, net	$ 27,886	$ 33,108	$ 25,021	$ 12,747	$ 12,747	$ 15,299
Deferred contract costs	5,359	2,947	769		1,906	1,346
Long-term deferred contract costs	9,388	5,952	2,116		3,829	2,973
Deferred revenues	$ 70,179	$ 61,200	$ 46,125	$ 32,000	$ 38,278	$ 31,458	$ 32,187

Revenue - Schedule of Activity

Revenue - Schedule of Activity Impacting the Deferred Contract Costs (Detail) - USD ($) $ in Thousands	6 Months Ended		9 Months Ended	12 Months Ended
	Dec. 31, 2019	Jul. 15, 2019	Sep. 30, 2021	Dec. 31, 2020	Jan. 01, 2019
Schedule of Activity Impacting the Deferred Contract Costs [Line Items]
Balance at beginning of period	$ 5,735		$ 8,899	$ 2,885
Costs amortized	(189)	$ (824)	(3,195)	(1,670)
Additional amounts deferred	3,074	2,239	9,043	7,684
Acquisition-related adjustment	(5,735)
Balance at end of period	2,885	5,735	14,747	8,899
Classified as:
Current	769	1,906	5,359	2,947	$ 1,346
Non-current	2,116	3,829	9,388	5,952	2,973
Total deferred contract costs (deferred commissions)	2,885		$ 14,747	$ 8,899
Cumulative Effect, Period of Adoption, Adjustment [Member]
Schedule of Activity Impacting the Deferred Contract Costs [Line Items]
Adoption of ASC 606		$ 4,320
Classified as:
Current	(769)				1,346
Non-current	$ (2,116)				$ 2,973

Revenue - Schedule of Activit_2

Revenue - Schedule of Activity Impacting Deferred Revenue Balances (Detail) - USD ($) $ in Thousands	6 Months Ended		9 Months Ended	12 Months Ended
	Dec. 31, 2019	Jul. 15, 2019	Sep. 30, 2021	Dec. 31, 2020
Deferred Revenue Arrangement [Line Items]
Balance at beginning of period	$ 38,278	$ 32,187	$ 61,200	$ 46,125
Acquisition adjustment	(6,278)
Revenue recognized	(40,045)	(45,458)	(119,841)	(118,317)
Additional amounts deferred	54,170	52,278	128,820	133,392
Balance at end of period	$ 46,125	38,278	$ 70,179	$ 61,200
Cumulative Effect, Period of Adoption, Adjustment [Member]
Deferred Revenue Arrangement [Line Items]
Adoption of ASC 606		$ (729)

Revenue - Schedule of Revenue R

Revenue - Schedule of Revenue Remaining Performance Obligation (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Current	$ 128,653	$ 114,284	$ 82,291
Noncurrent	78,900	58,250	40,475
Total	$ 207,553	$ 172,534	$ 122,766

Revenue - Schedule of Revenue_2

Revenue - Schedule of Revenue Remaining Performance Obligation (Parenthetical) (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Schedule of Revenue Remaining Performance Obligation [Line Items]
Revenue remaining performance obligation current	$ 128,653	$ 114,284	$ 82,291
Revenue remaining performance obligation noncurrent	78,900	58,250	40,475
Revenue remaining performance obligation	$ 207,553	172,534	122,766
Cumulative Effect, Period of Adoption, Adjustment [Member]
Schedule of Revenue Remaining Performance Obligation [Line Items]
Revenue remaining performance obligation current		121,623	90,237
Revenue remaining performance obligation noncurrent		51,368	32,957
Revenue remaining performance obligation		$ 172,991	$ 123,194

Accounts Receivable - Schedule

Accounts Receivable - Schedule of Accounts Receivable (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2019
Schedule Of Accounts Receivable [Line Items]
Accounts receivable	$ 28,739	$ 33,964	$ 25,471
Less: allowance for doubtful accounts	(853)	(856)	(450)
Accounts receivable, net	27,886	33,108	25,021	$ 14,932
Trade Accounts Receivable [Member]
Schedule Of Accounts Receivable [Line Items]
Accounts receivable	28,243	33,635	25,220
Unbilled Receivable [Member]
Schedule Of Accounts Receivable [Line Items]
Accounts receivable	$ 496	$ 329	$ 251

Property and Equipment - Schedu

Property and Equipment - Schedule Of Property Plant And Equipment (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 8,801	$ 6,159	$ 4,317
Less: accumulated depreciation and amortization	(4,104)	(2,911)	(1,759)
Property and equipment, net	4,697	3,248	2,558
Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	4,455	3,141	2,042
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	1,580	1,109	777
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	2,766	1,781	1,188
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 0	$ 128	$ 310

Property and Equipment - Additi

Property and Equipment - Additional Information (Detail) - USD ($) $ in Millions	6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2019	Jul. 15, 2019	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Depreciation and amortization	$ 0.5	$ 0.4	$ 1.2	$ 0.8	$ 1.2

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Schedule of Carrying Amounts of Goodwill and Intangible Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 499,286	$ 499,286	$ 476,998
Accumulated Amortization	(132,563)	(89,049)	(30,617)
Net Carrying Amount	366,723	410,237	446,381
Total goodwill and Intangible assets ,Gross	1,760,730	1,760,730	1,710,171
Total goodwill and Intangible assets and Accumulated Amortization	(132,563)	(89,049)	(30,617)
Total goodwill and Intangible assets , Net	1,628,167	1,671,681	1,679,554
Goodwill [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,261,444	1,261,444
Net Carrying Amount		1,261,444	1,233,173
Customer relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	370,030	370,030	358,130
Accumulated Amortization	(84,159)	(58,097)	(21,075)
Net Carrying Amount	285,871	311,933	337,055
Total goodwill and Intangible assets and Accumulated Amortization	(84,159)	(58,097)	(21,075)
Developed technologies [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	51,100	51,100	48,500
Accumulated Amortization	(15,648)	(10,218)	(3,206)
Net Carrying Amount	35,452	40,882	45,294
Total goodwill and Intangible assets and Accumulated Amortization	(15,648)	(10,218)	(3,206)
Tradenames [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	35,500	35,500	34,100
Accumulated Amortization	(4,510)	(2,952)	(928)
Net Carrying Amount	30,990	32,548	33,172
Total goodwill and Intangible assets and Accumulated Amortization	(4,510)	(2,952)	(928)
Data [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	42,656	42,656	36,268
Accumulated Amortization	(28,246)	(17,782)	(5,408)
Net Carrying Amount	14,410	24,874	30,860
Total goodwill and Intangible assets and Accumulated Amortization	$ (28,246)	$ (17,782)	$ (5,408)

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Schedule of Estimated Intangible Amortization Expense (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
2021		$ 58,143
2022		53,653
2023		45,709
2024		42,485
2025		38,296
Thereafter		171,951
Total	$ 366,723	$ 410,237	$ 446,381

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets - Schedule of Changes in Carrying Amount of Goodwill (Detail) - USD ($) $ in Thousands	Jul. 16, 2019	Dec. 31, 2019	Jul. 15, 2019	Dec. 31, 2020
Goodwill [Line Items]
Beginning ,Goodwill	$ 82,768	$ 82,768		$ 1,233,173
Ending, Goodwill	1,227,262	1,233,173	$ 82,768	1,261,444
HIMSS [Member]
Goodwill [Line Items]
Acquisition			19,145
Definitive Holdco [Member]
Goodwill [Line Items]
Beginning ,Goodwill	82,767	82,767
Acquisition	1,144,494
Ending, Goodwill	$ 1,227,261		$ 82,767
HSE [Member]
Goodwill [Line Items]
Acquisition		$ 5,911
Monocl [Member]
Goodwill [Line Items]
Acquisition				$ 28,271

Goodwill and Intangible Asset_5

Goodwill and Intangible Assets - Additional Information (Detail) - USD ($) $ in Millions	6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2019	Jul. 15, 2019	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 30.6	$ 2	$ 43.5	$ 43.5
Cost of Sales [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets			$ 15.9	$ 14.3	$ 19.4
Asset Management Income [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets					$ 58.4

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Payables and Accruals [Abstract]
Payroll and payroll-related	$ 7,246	$ 7,792	$ 3,879
Accrued interest	233	5,365	4,215
Contingent consideration, current	6,905	1,500
Sales taxes	1,146	649	1,916
Deferred rent	112	583	17
Other	3,654	1,432	321
Accrued expenses and other current liabilities	$ 19,296	$ 17,321	$ 10,348

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2019	Jul. 15, 2019	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Loss Contingencies [Line Items]
Sublease rental income						$ 0.1
Rent expense	$ 0.6	$ 0.5			$ 1.8
Selling, General and Administrative Expenses [Member]
Loss Contingencies [Line Items]
Rent expense			$ 2.1	$ 1.4

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Minimum Future Rental Payments (Detail) $ in Thousands	Dec. 31, 2020USD ($)
Commitments and Contingencies Disclosure [Abstract]
2021	$ 3,035
2022	2,673
2023	2,043
2024	2,338
2025	2,193
Thereafter	4,790
Total	$ 17,072

Commitments and Contingencies_3

Commitments and Contingencies - Schedule of Estimated Annual Minimum Purchase Commitments (Detail) $ in Thousands	Dec. 31, 2020USD ($)
Commitments and Contingencies Disclosure [Abstract]
2021	$ 5,396
2022	5,257
2023	5,098
2024	3,925
2025	2,370
Thereafter	0
Total	$ 22,046

Members' capital - Additional I

Members' capital - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended		12 Months Ended
	Dec. 31, 2019	Jul. 15, 2019	Dec. 31, 2020	May 24, 2021	Jul. 16, 2019	Dec. 31, 2018	Dec. 31, 2016
Total contributed capital	$ 3,997	$ 1,267,257	$ 31,804
Business Combination, Equity Interests Issued and Issuable			6,400
Common Stock, Shares, Issued				1
Common Stock, Shares Authorized				100			407,750
Common Stock, Shares, Outstanding				1
AIDH Buyer [Member]
Business Acquisition, Percentage of Voting Interests Acquired					100.00%
Capital Unit, Class A [Member]
Contributed capital units, issued	127,725,743
Price per share					$ 10
Total contributed capital	$ 1,267,300
Members' distribution payable	6,900
Business Combination, Equity Interests Issued and Issuable	$ 4,000		$ 25,400
Common Stock, Shares, Issued	127,125,435	7,750,000	130,245,990			7,750,000
Common Stock, Shares Authorized						7,750,000
Common Stock, Shares, Outstanding	127,125,435	268,853	130,245,990			7,750,000
Capital Unit, Class B [Member]
Common Stock, Shares, Issued		7,750,000
Common Stock, Shares Authorized						407,750
Common Stock, Shares, Outstanding		268,853				88,716
AIDH TopCo, LLC [Member]
Percentage of common stock issued and outstanding					100.00%

Equity-based Compensation - Add

Equity-based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		3 Months Ended		6 Months Ended		9 Months Ended			12 Months Ended
	Sep. 30, 2021	Jul. 31, 2019	Sep. 30, 2021	Jun. 30, 2021	Dec. 31, 2019	Jul. 15, 2019	Sep. 30, 2021	Sep. 15, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jul. 16, 2019
Share-based Payment Award, Vesting period		3 years
Share-based Payment Award, Shares granted					3,799,364	0				195,222
Share-based Payment Award, Number of shares vesting						0
Total unit-based compensation					$ 744	$ 5,807	$ 4,338		$ 1,330	$ 1,747
Unrecognized unit-based compensation expense										1,747
Capital Unit, Class B [Member]
Sharebased payment arrangement number of options vested							912,651
Share based compensation vested number of shares participation threshold after modification							578,217
2015 Incentive Equity Pool [Member]
Share-based Payment Award, Shares granted					0	48,592
Share-based Payment Award, Number of shares vesting					0	(180,137)
Equity Incentive Plan 2019 [Member]
Total unit-based compensation		$ 9,000
Sharebased compensation arrangements weighted average intrinsic value of shares forfeited		$ 27
Performance Shares [Member]
Share-based Payment Award, Shares granted								1,177,308
Total unit-based compensation					$ 0	$ 0				0
Unrecognized unit-based compensation expense										$ 4,300
Performance Shares [Member] | 2019 Incentive Equity Pool [Member]
Share-based Payment Award, Shares granted					1,899,682					97,611
Share-based Payment Award, Number of shares vesting					0					0
Total unit-based compensation					$ 0	0				$ 0
Performance Shares [Member] | 2015 Incentive Equity Pool [Member]
Total unit-based compensation					0	0				0
Performance Shares [Member] | Equity Incentive Plan 2019 [Member]
Total unit-based compensation			$ 200
Time Based [Member]
Share-based Payment Award, Shares granted								1,477,323
Share-based Payment Award, Number of shares vesting	(74,049)							(437,731)
Total unit-based compensation					$ 744	5,807	$ 1,500		$ 1,300	1,747
Unrecognized unit-based compensation expense										$ 4,400
Weighted average remaining requisite period										2 years 7 months 6 days
Sharebased compensation arrangement unrecognized expense	$ 18,400		18,400				$ 18,400
Weighted-average period over which cost not yet recognized is expected to be recognized							2 years 9 months 18 days
Time Based [Member] | 2019 Incentive Equity Pool [Member]
Share-based Payment Award, Shares granted					1,899,682					97,611
Share-based Payment Award, Number of shares vesting					0					(474,920)
Total unit-based compensation					$ 0	5,807				$ 0
Time Based [Member] | 2015 Incentive Equity Pool [Member]
Total unit-based compensation					$ 744	$ 0				$ 1,747
Time Based Restricted Stock Units [Member] | Equity Incentive Plan 2021 [Member]
Sharebased compensation arrangement unrecognized expense	$ 39,100		$ 39,100				$ 39,100
Sharebased compensation arrangement weighted average remaining term							4 years
Restricted Stock Units (RSUs) [Member] | Equity Incentive Plan 2021 [Member]
Total unit-based compensation							$ 400
Common Class B [Member]
Share-based Payment Award, Number of shares vesting										474,920
Sharebased compensation arrangement plan modification incremental costs		$ 72,149					$ 1,900
Common Class B [Member] | 2019 Incentive Equity Pool [Member]
Shares reserved for future issuance		8,088,877
Common Class B [Member] | 2015 Incentive Equity Pool [Member]
Shares reserved for future issuance													407,750
Common Class B [Member] | Performance Shares [Member]
Sharebased compensation arrangement accelerated vesting number		48,099
Common Class B [Member] | Time Based [Member]
Sharebased compensation arrangement accelerated vesting number		24,049
Class B Series A Units [Member]
Share-based Payment Award, Number of shares vesting												1
ClassB Series B Units [Member]
Share-based Payment Award, Number of shares vesting												73,418
ClassB Series C Units [Member]
Share-based Payment Award, Number of shares vesting												57,105
Class B Series D Units [Member]
Share-based Payment Award, Number of shares vesting												89,737
Class B Series E Units [Member]
Share-based Payment Award, Number of shares vesting											48,592
Common Class A [Member]
Total unit-based compensation				$ 300
Common Class A [Member] | Time Based Restricted Stock Units [Member] | Equity Incentive Plan 2021 [Member]
Common stock available for awards							8,989,039
Sharebased compensation arrangment Restrcited Stock units granted							1,464,681

Equity-based Compensation - Sch

Equity-based Compensation - Schedule of allocation of share based compensation costs by plan (Detail) - USD ($) $ in Thousands	6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2019	Jul. 15, 2019	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Allocated share based compensation expense	$ 744	$ 5,807	$ 4,338	$ 1,330	$ 1,747
Cost of revenue
Allocated share based compensation expense	28	256	79	46	62
Sales and marketing
Allocated share based compensation expense	213	4,252	567	380	473
Product development
Allocated share based compensation expense	126	665	341	267	356
General and administrative
Allocated share based compensation expense	377	634	3,351	637	856
Time Based [Member]
Allocated share based compensation expense	744	5,807	$ 1,500	$ 1,300	1,747
Performance Shares [Member]
Allocated share based compensation expense	0	0			0
2019 Incentive Equity Pool [Member] | Time Based [Member]
Allocated share based compensation expense	0	5,807			0
2019 Incentive Equity Pool [Member] | Performance Shares [Member]
Allocated share based compensation expense	0	0			0
2015 Incentive Equity Pool [Member] | Time Based [Member]
Allocated share based compensation expense	744	0			1,747
2015 Incentive Equity Pool [Member] | Performance Shares [Member]
Allocated share based compensation expense	$ 0	$ 0			$ 0

Equity-based Compensation - Sum

Equity-based Compensation - Summary of Nonvested Restricted Stock Shares Activity (Detail) - $ / shares	1 Months Ended	6 Months Ended		9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2019	Jul. 15, 2019	Sep. 15, 2021	Dec. 31, 2020	Dec. 31, 2019
Non-Vested Units, Beginning balance		0	0			0
Non-Vested Units, granted		3,799,364	0		195,222
Non-Vested Units, vested			0
Non-Vested Units, Ending balance			0
Weighted Average Grant Date Fair Value, Beginning balance		$ 0	$ 0			$ 0
Weighted Average Grant Date Fair Value, granted			0
Weighted Average Grant Date Fair Value, vested			0
Weighted Average Grant Date Fair Value, Ending balance			$ 0
Time Based [Member]
Non-Vested Units, Beginning balance	2,430,542			1,404,720
Non-Vested Units, Effect of Reorganization Transactions and IPO	(1,165,679)
Non-Vested Units, Performance-based units exchanged for time-based units	1,681,199
Non-Vested Units, granted				1,477,323
Non-Vested Units, vested	(74,049)			(437,731)
Non-Vested Units, forfeited	(72,149)			(13,770)
Non-Vested Units, Ending balance	2,799,864			2,430,542	1,404,720
Weighted Average Grant Date Fair Value, Beginning balance	$ 2.29			$ 3.65
Weighted Average Grant Date Fair Value, Effect of Reorganization Transactions and IPO	2.08
Weighted Average Grant Date Fair Value, Performance-based units exchanged for time-based units	1.74
Weighted Average Grant Date Fair Value, granted				1.41
Weighted Average Grant Date Fair Value, vested	2.75			3.64
Weighted Average Grant Date Fair Value, forfeited	2.78			3.65
Weighted Average Grant Date Fair Value, Ending balance	$ 2.02			$ 2.29	$ 3.65
Performance Shares [Member]
Non-Vested Units, Beginning balance	2,999,370			1,840,423
Non-Vested Units, Effect of Reorganization Transactions and IPO	(1,318,171)
Non-Vested Units, Performance-based units exchanged for time-based units	(1,681,199)
Non-Vested Units, granted				1,177,308
Non-Vested Units, forfeited				(18,361)
Non-Vested Units, Ending balance				2,999,370	1,840,423
Weighted Average Grant Date Fair Value, Beginning balance	$ 1.59			$ 2.35
Weighted Average Grant Date Fair Value, Effect of Reorganization Transactions and IPO	1.39
Weighted Average Grant Date Fair Value, Performance-based units exchanged for time-based units	$ 1.74
Weighted Average Grant Date Fair Value, granted				0.41
Weighted Average Grant Date Fair Value, forfeited				2.35
Weighted Average Grant Date Fair Value, Ending balance				$ 1.59	$ 2.35
2019 Incentive Equity Pool [Member] | Time Based [Member]
Non-Vested Units, Beginning balance				1,404,720	1,899,682
Non-Vested Units, granted		1,899,682			97,611
Non-Vested Units, vested		0			(474,920)
Non-Vested Units, forfeited		0			(117,653)
Non-Vested Units, Ending balance		1,899,682			1,404,720	1,899,682
Weighted Average Grant Date Fair Value, Beginning balance				$ 3.65	$ 3.65
Weighted Average Grant Date Fair Value, granted		$ 3.65			3.65
Weighted Average Grant Date Fair Value, vested		0			3.65
Weighted Average Grant Date Fair Value, forfeited		0			3.65
Weighted Average Grant Date Fair Value, Ending balance		$ 3.65			$ 3.65	$ 3.65
2019 Incentive Equity Pool [Member] | Performance Shares [Member]
Non-Vested Units, Beginning balance				1,840,423	1,899,682
Non-Vested Units, granted		1,899,682			97,611
Non-Vested Units, vested		0			0
Non-Vested Units, forfeited		0			(156,870)
Non-Vested Units, Ending balance		1,899,682			1,840,423	1,899,682
Weighted Average Grant Date Fair Value, Beginning balance				$ 2.35	$ 2.35
Weighted Average Grant Date Fair Value, granted		$ 2.35			2.35
Weighted Average Grant Date Fair Value, vested		0			0
Weighted Average Grant Date Fair Value, forfeited		0			2.35
Weighted Average Grant Date Fair Value, Ending balance		$ 2.35			$ 2.35	$ 2.35
2015 Incentive Equity Pool [Member]
Non-Vested Units, Beginning balance		0	131,545		0	131,545
Non-Vested Units, granted		0	48,592
Non-Vested Units, vested		0	(180,137)
Non-Vested Units, forfeited		0	0
Non-Vested Units, Ending balance		0	0			0
Weighted Average Grant Date Fair Value, Beginning balance		$ 0	$ 9		$ 0	$ 9
Weighted Average Grant Date Fair Value, granted		0	98.75
Weighted Average Grant Date Fair Value, vested		0	33.21
Weighted Average Grant Date Fair Value, forfeited		0	0
Weighted Average Grant Date Fair Value, Ending balance		$ 0	$ 0			$ 0

Equity-based Compensation - S_2

Equity-based Compensation - Summary of Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value (Detail)	Dec. 31, 2021	Sep. 30, 2021	Dec. 31, 2019	Dec. 31, 2020
Expected option term	5 years 6 months		5 years 6 months	5 years 6 months
Risk-free rate of return	1.73%		1.73%	1.73%
Applied volatility	35.00%	30.00%	35.00%	35.00%
Maximum [Member]
Expected option term		8 months 12 days
Risk-free rate of return		0.06%
Minimum [Member]
Expected option term		3 months 18 days
Risk-free rate of return		0.01%

Equity-Based Compensation - S_3

Equity-Based Compensation - Schedule Of Unvested Restricted Stock Options (Detail) - Equity Incentive Plan 2021 [Member]	9 Months Ended
	Sep. 30, 2021$ / sharesshares
Time Based Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock Units, Unvested at beginning of period | shares	0
Restricted Stock Units, Granted | shares	1,300,328
Restricted Stock Units, Vested | shares	0
Restricted Stock Units, Forfeited | shares	(2,656)
Restricted Stock Units, Unvested at end of period | shares	1,297,672
Weighted Average Grant Date Fair Value, Unvested at beginning of period | $ / shares	$ 0
Weighted Average Grant Date Fair Value, Granted | $ / shares	27
Weighted Average Grant Date Fair Value, Vested | $ / shares	0
Weighted Average Grant Date Fair Value, Forfeited | $ / shares	27
Weighted Average Grant Date Fair Value, Unvested at end of period | $ / shares	$ 27
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock Units, Unvested at beginning of period | shares	0
Restricted Stock Units, Granted | shares	164,353
Restricted Stock Units, Vested | shares	0
Restricted Stock Units, Forfeited | shares	0
Restricted Stock Units, Unvested at end of period | shares	164,353
Weighted Average Grant Date Fair Value, Unvested at beginning of period | $ / shares	$ 0
Weighted Average Grant Date Fair Value, Granted | $ / shares	27
Weighted Average Grant Date Fair Value, Vested | $ / shares	0
Weighted Average Grant Date Fair Value, Forfeited | $ / shares	0
Weighted Average Grant Date Fair Value, Unvested at end of period | $ / shares	$ 27

Retirement Plan - Additional In

Retirement Plan - Additional Information (Detail) - USD ($) $ in Millions	6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2019	Jul. 15, 2019	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Retirement Benefits [Abstract]
Employer Contribution Amount	$ 0.5	$ 0.6	$ 1.7	$ 1.1	$ 1.6

Long-term debt - Schedule of Lo

Long-term debt - Schedule of Long-term Debt Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 17, 2021	Dec. 31, 2020	Dec. 31, 2019	Jul. 16, 2019
Debt Instrument [Line Items]
Principal			$ 472,742	$ 451,916
Unamortized debt issuance costs / financing costs			(10,865)	(12,567)
Total debt, net			461,877	439,349
Less: current portion of long-term debt	$ 6,875		4,680	4,500
Long-term debt	265,388		457,197	434,849
2019 Term Loan
Debt Instrument [Line Items]
Principal	450,000	$ 442,100	444,375	448,875	$ 450,000
Unamortized debt issuance costs / financing costs			(10,865)	(12,567)
Total debt, net			433,510	436,308
Paid in kind interest on 2019 Term Note
Debt Instrument [Line Items]
Principal			10,412	3,041	100,000
Total debt, net			10,412	$ 3,041
2019 Delayed Draw Term Loan
Debt Instrument [Line Items]
Principal			17,955		$ 100,000
Total debt, net			$ 17,955
2021 Term Loan
Debt Instrument [Line Items]
Principal	275,000
Unamortized debt issuance costs / financing costs	(2,737)
Total debt, net	$ 272,263

Long-term debt - Schedule of Fu

Long-term debt - Schedule of Future principal payments (Detail) $ in Thousands	Dec. 31, 2020USD ($)
Maturities of Long-term Debt [Abstract]
2021	$ 4,680
2022	4,680
2023	4,680
2024	4,680
2025	4,680
Thereafter	449,342
Long-term Debt	$ 472,742

Long-term debt - Additional Inf

Long-term debt - Additional Information (Detail) $ in Thousands	Sep. 17, 2021USD ($)	Jul. 16, 2019USD ($)	Jan. 08, 2019USD ($)	Dec. 31, 2019USD ($)	Jul. 15, 2019USD ($)	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2019USD ($)	Oct. 01, 2020USD ($)
Debt Instrument [Line Items]
Debt instrument face amount				$ 451,916				$ 472,742	$ 451,916	$ 451,916
Long-term Debt				439,349				461,877	439,349	439,349
Payments of Financing Costs										12,500
Amortization of Debt Issuance Costs and Discounts					$ 0				900
Unamortized financing costs				600				500	600	600
Debt, paid in kind interest				3,041			$ 7,371	7,371
Loss on extinguishment of debt						$ (9,843)
Unamortized debt issuance costs				12,600		3,500		10,900	12,600	12,600
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit		$ 25,000
Payments of Financing Costs										1,600
2019 Term Loan
Debt Instrument [Line Items]
Debt instrument face amount	$ 442,100	$ 450,000		$ 448,875		$ 450,000		444,375	$ 448,875	$ 448,875
Debt Instrument, Maturity Date		Jul. 16, 2026				Jul. 16, 2026
Debt Instrument, Unamortized Discount		$ 11,300				$ 14,100		$ 13,400
Debt Instrument, Interest Rate, Stated Percentage	6.25%			7.404%				6.50%	7.404%	7.404%
Debt Instrument, Frequency of Periodic Payment										Quarterly
Repayments of Debt										$ 1,100
Debt Instrument, Periodic Payment Terms, Balloon Payment to be Paid				$ 419,600					$ 419,600	419,600
Long-term Debt				436,308				$ 433,510	436,308	436,308
Proceeds from debt	$ 275,000
Line of credit								454,800
Debt, paid in kind interest	10,400					100,000		10,400
Interest payable on debt	4,200
Proceeds from initial public offering	199,600
Loss on extinguishment of debt	9,900
Line of credit periodic payment						1,100
Repayment of debt						419,600
Interest expense, debt						1,500	$ 1,500
2019 Term Loan | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt Instrument, Unamortized Discount											$ 700
Unamortized financing costs				500					500	500
2019 Term Loan | Maximum [Member]
Debt Instrument [Line Items]
Debt instrument face amount		100,000
Paid in kind interest on 2019 Term Note
Debt Instrument [Line Items]
Debt instrument face amount		100,000		$ 3,041				10,412	$ 3,041	$ 3,041
Debt Instrument, Interest Rate, Stated Percentage				8.404%					8.404%	8.404%
Long-term Debt				$ 3,041				10,412	$ 3,041	$ 3,041
Paid in kind interest on 2019 Term Note | Maximum [Member]
Debt Instrument [Line Items]
Debt instrument face amount		450,000
2019 Delayed Draw Term Loan
Debt Instrument [Line Items]
Debt instrument face amount		$ 100,000						17,955
Debt Instrument, Maturity Date		Jul. 16, 2026
Debt Instrument, Unamortized Discount		$ 1,300						$ 1,300			$ 200
Debt Instrument, Interest Rate, Stated Percentage		6.50%
Debt Instrument, Frequency of Periodic Payment		quarterly						quarterly
Long-term Debt								$ 17,955
Proceeds from debt								18,000
Debt Instruments Quarterly principal payments Rate		0.25
Line of Credit drawn		$ 18,000		25,000
Debt instrument accrued interest	17,900
2019 Delayed Draw Term Loan | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit drawn						$ 0
Line of credit								0
Line of credit expiration date						Sep. 17, 2021
Line of Credit
Debt Instrument [Line Items]
Debt Instrument, Maturity Date			Jan. 8, 2021
Debt Instrument, Frequency of Periodic Payment										Quarterly
Debt Instruments Quarterly principal payments Rate										0.3
Line of credit facility maximum borrowing capacity			$ 15,000
Line of Credit drawn										$ 13,000
Repayments of Lines of Credit										13,000
Line of Credit | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Jul. 16, 2024
Debt Instrument, Frequency of Periodic Payment		Quarterly
Debt Instruments Quarterly principal payments Rate		0.5
Line of credit facility maximum borrowing capacity		$ 25,000
Line of Credit drawn								25,000
Line of credit				0				0	0	0
2021 Term Loan
Debt Instrument [Line Items]
Debt instrument face amount						$ 275,000
Debt Instrument, Interest Rate, Stated Percentage						2.37%
Debt Instrument, Frequency of Periodic Payment						quarterly
Long-term Debt						$ 272,263
Proceeds from debt	$ 474,600
Line of credit facility maximum borrowing capacity						275,000
Line of credit						275,000
Line of credit facility annual principal amount						220,000
Unamortized debt issuance costs						2,800
2021 Term Loan | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt instrument face amount		$ 25,000
Line of credit facility maximum borrowing capacity						75,000
Line of credit						0
Unamortized debt issuance costs						$ 800
2021 Term Loan | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage						5.00%
Line of credit facility unused capacity commitment fee percentage						0.30%
2021 Term Loan | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage						2.50%
Line of credit facility unused capacity commitment fee percentage						0.25%
Principal Payments [Member]
Debt Instrument [Line Items]
Debt instrument face amount				350,000					350,000	350,000
2020 Term Loan
Debt Instrument [Line Items]
Debt instrument face amount								350,000
Long-term Debt				451,900				454,800	451,900	451,900
Paid in kind interest on 2019 Term Note
Debt Instrument [Line Items]
Debt instrument face amount				100,000				100,000	100,000	100,000
Long-term Debt				3,000				10,400	3,000	3,000
2019 Delayed Draw Term Loan
Debt Instrument [Line Items]
Long-term Debt				$ 0				$ 18,000	$ 0	$ 0

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Significant Unobservable Inputs Used Recurring Level 3 Fair Value Measurements (Detail) - Fair Value, Inputs, Level 3 [Member] - Earnout Liability [Member] $ in Thousands	Sep. 30, 2021USD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Jul. 15, 2019USD ($)	Dec. 31, 2018USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 6,905	$ 5,236
Discount Rate		6.5
Income Approach Method [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 6,905	$ 6,905
Measurement Input, Discount Rate [Member] | Income Approach Method [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Discount Rate	2.38	2.38

Fair Value Measurements - Sch_2

Fair Value Measurements - Schedule of Reconciliation of Earnout Liabilities Measeured at Fair Value (Detail) - Fair Value, Inputs, Level 3 [Member] - Earnout Liability [Member] - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	$ 5,236
Additions		2,600
Net change in fair value and other adjustments	3,169	2,636
Payments	(1,500)
Balance at end of period	$ 6,905	$ 5,236

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Thousands	Apr. 30, 2021	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Payment of contingent consideration		$ 1,500
Earnout Liability [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value of contingent consideration		6,900	$ 5,200
Fair value of contingent consideration current		6,900	1,500
Fair value of contingent consideration noncurrent		0	3,700
Payment of contingent consideration	$ 1,500
Maximum [Member] | Earnout Liability [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Earnout potential payments		10,000	15,000
Minimum [Member] | Earnout Liability [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Earnout potential payments		$ 0	$ 0

Organization - Additional Infor

Organization - Additional Information (Detail)	May 24, 2021
Definitive Healthcare Corp [Member]
Entity Incorporation, Date of Incorporation	May 5, 2021

Stockholders' Equity and Memb_3

Stockholders' Equity and Members' Equity - Schedule Of Common Stock Units Authorized Issued And Outstanding (Detail) - shares	Dec. 31, 2020	Dec. 31, 2019
Common Class A [Member]
Stockholders Equity And Members Deficit [Line Items]
Authorized, issued and outstanding Class A units	130,245,990
Authorized Class B units	130,245,990	127,125,435
Issued Class B units	130,245,990	127,125,435
Outstanding Class B units (Vested Class B units)	130,245,990	127,125,435
Common Class B [Member]
Stockholders Equity And Members Deficit [Line Items]
Authorized Class B units	8,088,877	8,088,877
Issued Class B units	3,720,063	3,799,364
Outstanding Class B units (Vested Class B units)	474,920	0

Stockholders' Equity and Memb_4

Stockholders' Equity and Members' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	6 Months Ended		9 Months Ended		12 Months Ended
	Jun. 30, 2021	Dec. 31, 2019	Jul. 15, 2019	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	May 24, 2021	Dec. 31, 2016
Class of Stock [Line Items]
Allocated share based compensation expense		$ 744	$ 5,807	$ 4,338	$ 1,330	$ 1,747
Common stock shares authorized							100	407,750
Common stock par or stated value per share							$ 0.01
Common stock shares issued							1
Common Class A [Member]
Class of Stock [Line Items]
Stock issued during period shares for services	363,516
Procceds from issuance of common stock	$ 5,800
Capital contribution from common shares issued	5,500
Allocated share based compensation expense	$ 300

Income Taxes - Schedule of Reco

Income Taxes - Schedule of Reconciliation of Income Tax Expense (Detail)	6 Months Ended	9 Months Ended		12 Months Ended
	Dec. 31, 2019	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Federal income tax expense at statutory rate	21.00%			21.00%	0.00%
State income tax, net of federal benefit	0.04%			(0.14%)	0.00%
Permanent differences	(2.73%)			(0.98%)	0.00%
Research and development credit	0.00%			0.00%	0.00%
Foreign rate differential	0.00%			(0.01%)	0.00%
Change in valuation allowance	0.00%			0.60%	0.00%
Provision to return adjustments	0.00%			0.46%	0.00%
Other	(0.04%)			6.50%	0.37%
Pass through income not subject to tax	(18.27%)			(27.55%)	0.01%
Effective income tax rate	0.00%	0.30%	0.00%	(0.12%)	0.38%

Income Taxes - Schedule of Comp

Income Taxes - Schedule of Components of Income Tax Provision or Benefit (Detail) - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
	Dec. 31, 2019	Jul. 15, 2019	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Current tax provision: Federal			$ 10
Current tax provision: State			1
Total current tax provision			11
Deferred tax provision: Federal			58
Deferred tax provision: State		$ 49	(7)
Total deferred tax provision		49	51
Total provision		$ 49	$ 62

Income Taxes - Schedule of Co_2

Income Taxes - Schedule of Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Foreign, U.S. and state net operating loss carryforwards	$ 1,517	$ 212
Accrued Expenses	12
Unrealized foreign exchange losses	62
Subtotal	1,591	212
Less valuation allowance	(1,430)
Total deferred tax assets	161	212
Net deferred tax assets	$ 161	$ 212

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	6 Months Ended	9 Months Ended		12 Months Ended
	Dec. 31, 2019	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	$ 212			$ 1,517	$ 212
Valuation allowance				1,430
Increase in valuation allowance				$ 1,400
Change in ownership interest				50.00%
Uncertain tax positions		$ 0		$ 0
Effective income tax rate	0.00%	0.30%	0.00%	(0.12%)	0.38%
Income tax examination liability under tax receivable agreement		$ 146,100
Effective income tax rate, tax settlements		85.00%
Effective income tax rate, contingencies		15.00%
Deferred tax liability		$ 71,300
Domestic Tax Authority [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	$ 1,100			$ 600	$ 1,100
State and Local Jurisdiction [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	$ 1,500			600	$ 1,500
Foreign Tax Authority [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards				6,900
Valuation allowance				$ 1,400

Loss Per Share - Additional Inf

Loss Per Share - Additional Information (Detail) - shares	6 Months Ended	12 Months Ended
	Jul. 15, 2019	Dec. 31, 2020
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Share-based compensation arrangement, number of units vested	0
Common Class B [Member]
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Share-based compensation arrangement, number of units vested		474,920

Loss Per Share - Schedule of Re

Loss Per Share - Schedule of Reconciliation of Earnings Per Share Basic and Diluted (Detail) - USD ($) $ in Thousands	6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2019	Jul. 15, 2019	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Numerator
Less: Net loss attributable to noncontrolling interests			$ (5,172)
Net loss attributable to Definitive Healthcare Corp.	$ (49,266)	$ 12,868	(46,493)	$ (35,295)	$ (51,157)
Common Class A [Member]
Numerator
Net loss			(46,493)
Less: Net loss attributable to Definitive OpCo before Reorganization Transactions			(33,343)
Less: Net loss attributable to noncontrolling interests			(5,172)
Net loss attributable to Definitive Healthcare Corp.			$ (7,978)

Loss Per Share - Schedule Of Co

Loss Per Share - Schedule Of Computation Of Earnings Per Share Basic And Diluted (Detail) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended		9 Months Ended			12 Months Ended
	Dec. 31, 2019	Jul. 15, 2019	Sep. 30, 2021		Sep. 30, 2020	Dec. 31, 2020
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Net loss	$ (49,266)	$ 12,868	$ (46,493)		$ (35,295)	$ (51,157)
Weighted average number of shares of Class A outstanding	126,794,329		88,263,333	[1]		127,682,376
Net loss per share, basic and diluted	$ (0.39)					$ (0.40)
Common Class A [Member]
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Net loss			$ (7,978)
Weighted average number of shares of Class A outstanding			88,263,333,000
Net loss per share, basic and diluted			$ (0.09)
[1]	Basic and diluted net loss per share of Class A Common Stock is applicable only for the period from September 15, 2021 through September 30, 2021, which is the period following the initial public offering (“IPO”) and related Reorganization Transactions (as defined in Note 1 to the Unaudited Consolidated Financial Statements). See Note 16 for the number of shares used in the computation of net loss per share of Class A Common Stock and the basis for the computation of net loss per share.

Loss Per Share - Schedule of Po

Loss Per Share - Schedule of Potentially Dilutive Securities Excluded From The Computation Of Diluted Net Loss Per Share (Detail)	9 Months Ended
	Sep. 30, 2021shares
Definitive OpCo Units [Member]
Antidilutive securities excluded from computation of earnings per share, amount	57,192,893

Segment and Geographic Data - S

Segment and Geographic Data - Summary Of Revenues By Geographic Area Presented Based Upon The Location Of The Customer (Detail) - USD ($) $ in Thousands	6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2019	Jul. 15, 2019	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	$ 40,045	$ 45,458	$ 119,841	$ 84,659	$ 118,317
United States [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	$ 40,045	$ 45,458	114,339	$ 84,659	117,755
Rest of World [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue			$ 5,502		$ 562

Segment and Geographic Data -_2

Segment and Geographic Data - Summary of Long-lived Assets by Geographical Region are Based on the Location of the Legal Entity that Owns the Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting, Asset Reconciling Item [Line Items]
Total long-lived assets	$ 4,697	$ 3,248	$ 2,558
United States [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total long-lived assets	4,311	3,120	$ 2,558
Rest of World [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total long-lived assets	$ 386	$ 128

Segment and Geographic Data - A

Segment and Geographic Data - Additional Information (Detail) - Segment	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Segment Reporting [Abstract]
Number of operating segments	1	1

Related Parties - Additional In

Related Parties - Additional Information (Detail) - USD ($) $ in Thousands	Sep. 17, 2021	Jun. 30, 2021	Dec. 31, 2019	Jul. 15, 2019	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Related Party Transaction [Line Items]
Revenue from related parties					$ 700	$ 600
Related party transaction, expenses from transactions with related party					200
Related party transaction, Revenue			$ 40,045	$ 45,458	119,841	84,659	$ 118,317
Related party transaction, Receivables			$ 100		$ 100	$ 700	100	$ 100
Common Class A [Member]
Related Party Transaction [Line Items]
Stock issued during period shares for services		363,516
Procceds from issuance of common stock		$ 5,800
IPO [Member]
Related Party Transaction [Line Items]
Procceds from issuance of common stock	$ 452,800
IPO [Member] | Common Class A [Member]
Related Party Transaction [Line Items]
Percentage reserved from common shares by underwriters		5.00%
Sponsors [Member]
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party							100	0
Related Party [Member]
Related Party Transaction [Line Items]
Related party transaction, Revenue							$ 400	$ 200
Due to related parties	$ 900
Richard Booth [Member] | IPO [Member] | Common Class A [Member]
Related Party Transaction [Line Items]
Stock issued during period shares for services		7,407
Samuel A Hamood [Member] | IPO [Member] | Common Class A [Member]
Related Party Transaction [Line Items]
Stock issued during period shares for services		37,037

Noncontrolling Interest - Addit

Noncontrolling Interest - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2021shares
Non controlling interest number of shares held	88,263,333
Definitive Holdco [Member]
Noncontrolling interest, ownership percentage by noncontrolling owners	60.70%

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - Subsequent Event [Member] $ in Millions	Oct. 07, 2021USD ($)shares
Common Class A [Member] | Restricted Stock Units (RSUs) [Member] | From One Year Anniversary Of The Grant Over The Subsequent Three Years [Member]
Subsequent Event [Line Items]
Deferred compensation arrangement with individual, cash awards granted, percentage	6.25%
Deferred Bonus [Member] | Common Class A [Member] | From One Year Anniversary Of The Grant Over The Subsequent Two Years [Member]
Subsequent Event [Line Items]
Deferred compensation arrangement with individual, cash awards granted, percentage	8.33%
Deferred Bonus [Member] | Common Class A [Member] | Restricted Stock Units (RSUs) [Member] | From One Year Anniversary Of The Grant Over The Subsequent Three Years [Member]
Subsequent Event [Line Items]
Deferred compensation arrangement with individual, cash awards granted, percentage	25.00%
Deferred compensation arrangement with individual, shares issued	433,550
Deferred Bonus [Member] | Common Class A [Member] | Second Restricted Stock Units RSU [Member] | From One Year Anniversary Of The Grant Over The Subsequent Two Years [Member]
Subsequent Event [Line Items]
Deferred compensation arrangement with individual, cash awards granted, percentage	33.00%
Deferred compensation arrangement with individual, shares issued	216,450
President [Member] | Deferred Bonus [Member]
Subsequent Event [Line Items]
Deferred compensation arrangement with individual, cash awards granted, percentage	68.00%
Robert Musslewhite [Member]
Subsequent Event [Line Items]
Salaries paid | $	$ 0.4