0001595974-21-000066 | 10-Q | XBRL Viewer

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Cover Page - shares	9 Months Ended
Cover Page - shares	Sep. 30, 2021	Oct. 27, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2021
Document Transition Report	false
Entity File Number	001-36384
Entity Registrant Name	MAGNITE, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	20-8881738
Entity Address, Address Line One	1250 Broadway,
Entity Address, Address Line Two	15th Floor
Entity Address, City or Town	New York,
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10001
City Area Code	212
Local Phone Number	243-2769
Title of 12(b) Security	Common stock, par value $0.00001 per share
Trading Symbol	MGNI
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		131,812,867
Entity Central Index Key	0001595974
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 188,182	$ 117,676
Accounts receivable, net	765,076	471,666
Prepaid expenses and other current assets	20,992	17,729
TOTAL CURRENT ASSETS	974,250	607,071
Property and equipment, net	32,759	23,681
Right-of-use lease asset	64,591	39,599
Internal use software development costs, net	19,130	16,160
Intangible assets, net	463,571	89,884
Other assets, non-current	6,062	4,440
Goodwill	972,747	158,125
TOTAL ASSETS	2,533,110	938,960
Current liabilities:
Accounts payable and accrued expenses	828,501	509,315
Lease liabilities, current	15,033	9,813
Debt, current	3,600	0
Other current liabilities	11,773	3,070
TOTAL CURRENT LIABILITIES	858,907	522,198
Debt, non-current, net of debt issuance costs	719,333	0
Deferred tax liability, net	19,488	199
Lease liabilities, non-current	55,999	32,278
Other liabilities, non-current	2,618	2,672
TOTAL LIABILITIES	1,656,345	557,347
Commitments and contingencies (Note 12)
STOCKHOLDERS' EQUITY
Preferred stock, $0.00001 par value, 10,000 shares authorized at September 30, 2021 and December 31, 2020; 0 shares issued and outstanding at September 30, 2021 and December 31, 2020	0	0
Common stock, $0.00001 par value; 500,000 shares authorized at September 30, 2021 and December 31, 2020; 131,789 and 114,029 shares issued and outstanding at September 30, 2021 and December 31, 2020, respectively	2	2
Additional paid-in capital	1,273,093	777,084
Accumulated other comprehensive loss	(1,426)	(957)
Accumulated deficit	(394,904)	(394,516)
TOTAL STOCKHOLDERS' EQUITY	876,765	381,613
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 2,533,110	$ 938,960

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Preferred stock, par value (usd per share)	$ 0.00001	$ 0.00001
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (usd per share)	$ 0.00001	$ 0.00001
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Common stock, shares, issued (in shares)	131,789,000	114,029,000
Common stock, shares, outstanding (in shares)	131,789,000	114,029,000

Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Statement [Abstract]
Revenue	$ 131,871	$ 60,982	$ 307,127	$ 139,625
Expenses:
Cost of revenue	63,541	21,031	134,823	56,579
Sales and marketing	52,260	21,761	118,122	53,059
Technology and development	21,059	13,562	53,436	37,318
General and administrative	16,535	13,314	47,673	38,221
Merger, acquisition, and restructuring costs	2,424	2,254	37,778	16,677
Total expenses	155,819	71,922	391,832	201,854
Loss from operations	(23,948)	(10,940)	(84,705)	(62,229)
Other (income) expense:
Interest (income) expense, net	7,280	30	12,595	(112)
Other income	(955)	(1,194)	(3,317)	(2,487)
Foreign exchange (gain) loss, net	(1,246)	293	(1,358)	(845)
Total other (income) expense, net	5,079	(871)	7,920	(3,444)
Loss before income taxes	(29,027)	(10,069)	(92,625)	(58,785)
Provision (benefit) for income taxes	(4,708)	446	(92,237)	533
Net loss	$ (24,319)	$ (10,515)	$ (388)	$ (59,318)
Net loss per share:
Basic (usd per share)	$ (0.18)	$ (0.10)	$ 0	$ (0.65)
Diluted (usd per share)	$ (0.18)	$ (0.10)	$ 0	$ (0.65)
Weighted average shares used to compute net loss per share:
Basic (in shares)	131,501	110,416	124,325	91,371
Diluted (in shares)	131,501	110,416	124,325	91,371

Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement of Comprehensive Income [Abstract]
Net loss	$ (24,319)	$ (10,515)	$ (388)	$ (59,318)
Other comprehensive income (loss):
Foreign currency translation adjustments	(525)	18	(469)	(2,540)
Other comprehensive income (loss)	(525)	18	(469)	(2,540)
Comprehensive loss	$ (24,844)	$ (10,497)	$ (857)	$ (61,858)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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+ Details

Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning Balance (in shares) at Dec. 31, 2019		53,888
Beginning Balance at Dec. 31, 2019	$ 111,936	$ 1	$ 453,064	$ (45)	$ (341,084)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options (in shares)		27
Exercise of common stock options	23		23
Issuance of common stock related to RSU vesting (in shares)		1,861
Shares withheld related to net share settlement (in shares)		(716)
Shares withheld related to net share settlement	(7,485)		(7,485)
Stock-based compensation	4,218		4,218
Other comprehensive income (loss)	(789)			(789)
Net income (loss)	(9,675)				(9,675)
Ending Balance (in shares) at Mar. 31, 2020		55,060
Ending Balance at Mar. 31, 2020	98,228	$ 1	449,820	(834)	(350,759)
Beginning Balance (in shares) at Dec. 31, 2019		53,888
Beginning Balance at Dec. 31, 2019	111,936	$ 1	453,064	(45)	(341,084)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive income (loss)	(2,540)
Net income (loss)	(59,318)
Ending Balance (in shares) at Sep. 30, 2020		110,712
Ending Balance at Sep. 30, 2020	356,131	$ 2	759,116	(2,585)	(400,402)
Beginning Balance (in shares) at Mar. 31, 2020		55,060
Beginning Balance at Mar. 31, 2020	98,228	$ 1	449,820	(834)	(350,759)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options (in shares)		746
Exercise of common stock options	2,276		2,276
Issuance of common stock related to employee stock purchase plan (in shares)		159
Issuance of common stock related to employee stock purchase plan	693		693
Issuance of common stock related to RSU vesting (in shares)		1,904
Shares withheld related to net share settlement (in shares)		(107)
Shares withheld related to net share settlement	(349)		(349)
Issuance of common stock associates with the Merger, (in shares)		52,099
Issuance of common stock associated with the Merger	275,773	$ 1	275,772
Exchange of stock options and RSU related to Merger	11,646		11,646
Stock-based compensation	10,101		10,101
Other comprehensive income (loss)	(1,769)			(1,769)
Net income (loss)	(39,128)				(39,128)
Ending Balance (in shares) at Jun. 30, 2020		109,861
Ending Balance at Jun. 30, 2020	357,471	$ 2	749,959	(2,603)	(389,887)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options (in shares)		563
Exercise of common stock options	1,569		1,569
Issuance of common stock related to RSU vesting (in shares)		289
Shares withheld related to net share settlement (in shares)		(1)
Shares withheld related to net share settlement	(7)		(7)
Stock-based compensation	7,595		7,595
Other comprehensive income (loss)	18			18
Net income (loss)	(10,515)				(10,515)
Ending Balance (in shares) at Sep. 30, 2020		110,712
Ending Balance at Sep. 30, 2020	$ 356,131	$ 2	759,116	(2,585)	(400,402)
Beginning Balance (in shares) at Dec. 31, 2020	114,029	114,029
Beginning Balance at Dec. 31, 2020	$ 381,613	$ 2	777,084	(957)	(394,516)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options (in shares)		733
Exercise of common stock options	5,785		5,785
Issuance of common stock related to RSU vesting (in shares)		1,351
Stock-based compensation	7,108		7,108
Capped call options	(38,960)		(38,960)
Other comprehensive income (loss)	(313)			(313)
Net income (loss)	(12,877)				(12,877)
Ending Balance (in shares) at Mar. 31, 2021		116,113
Ending Balance at Mar. 31, 2021	$ 342,356	$ 2	751,017	(1,270)	(407,393)
Beginning Balance (in shares) at Dec. 31, 2020	114,029	114,029
Beginning Balance at Dec. 31, 2020	$ 381,613	$ 2	777,084	(957)	(394,516)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive income (loss)	(469)
Net income (loss)	$ (388)
Ending Balance (in shares) at Sep. 30, 2021	131,789	131,789
Ending Balance at Sep. 30, 2021	$ 876,765	$ 2	1,273,093	(1,426)	(394,904)
Beginning Balance (in shares) at Mar. 31, 2021		116,113
Beginning Balance at Mar. 31, 2021	342,356	$ 2	751,017	(1,270)	(407,393)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options (in shares)		384
Exercise of common stock options	1,480		1,480
Issuance of common stock related to employee stock purchase plan (in shares)		121
Issuance of common stock related to employee stock purchase plan	1,154		1,154
Issuance of common stock related to RSU vesting (in shares)		2,208
Issuance of common stock associated with the SpotX Acquisition (in shares)		12,374
Issuance of common stock associated with the SpotX Acquisition	495,591		495,591
Stock-based compensation	9,928		9,928
Other comprehensive income (loss)	369			369
Net income (loss)	36,808				36,808
Ending Balance (in shares) at Jun. 30, 2021		131,200
Ending Balance at Jun. 30, 2021	887,686	$ 2	1,259,170	(901)	(370,585)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options (in shares)		275
Exercise of common stock options	1,482		1,482
Issuance of common stock related to RSU vesting (in shares)		314
Stock-based compensation	12,441		12,441
Other comprehensive income (loss)	(525)			(525)
Net income (loss)	$ (24,319)				(24,319)
Ending Balance (in shares) at Sep. 30, 2021	131,789	131,789
Ending Balance at Sep. 30, 2021	$ 876,765	$ 2	$ 1,273,093	$ (1,426)	$ (394,904)

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
OPERATING ACTIVITIES:
Net loss	$ (388)	$ (59,318)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	97,084	36,157
Stock-based compensation	28,521	21,298
(Gain) loss on disposal of property and equipment	78	(17)
Provision for doubtful accounts	217	31
Amortization of debt issuance costs	3,223	0
Non-cash lease expense	1,825	(601)
Deferred income taxes	(91,540)	837
Unrealized foreign currency gain	(2,578)	(2,108)
Changes in operating assets and liabilities:
Accounts receivable	(92,131)	(46,145)
Prepaid expenses and other assets	(297)	(2,896)
Accounts payable and accrued expenses	113,795	23,464
Other liabilities	191	5,260
Net cash provided by (used in) operating activities	58,000	(24,038)
INVESTING ACTIVITIES:
Purchases of property and equipment	(13,985)	(4,211)
Capitalized internal use software development costs	(8,525)	(6,894)
Cash (used in), net of cash acquired, in merger and acquisition activities	(653,060)
Cash (used in), net of cash acquired, in merger and acquisition activities		54,595
Net cash (used in) provided by investing activities	(675,570)	43,490
FINANCING ACTIVITIES:
Proceeds from Convertible Senior Notes offering	400,000	0
Proceeds from issuance of debt, net of debt discount	349,200	0
Payment for capped call options	(38,960)	0
Payment for debt issuance costs	(30,378)	0
Proceeds from exercise of stock options	8,747	3,868
Proceeds from issuance of common stock under employee stock purchase plan	1,154	693
Repayment of debt	(900)	0
Taxes paid related to net share settlement	0	(7,841)
Net cash provided by (used in) financing activities	688,863	(3,280)
EFFECT OF EXCHANGE RATE CHANGES ON CASH, CASH EQUIVALENTS AND RESTRICTED CASH	(591)	41
CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	70,702	16,213
CASH, CASH EQUIVALENTS AND RESTRICTED CASH — Beginning of period	117,731	88,888
CASH, CASH EQUIVALENTS AND RESTRICTED CASH — End of period	188,433	105,101
RECONCILIATION OF CASH, CASH EQUIVALENTS AND RESTRICTED CASH TO CONSOLIDATED BALANCE SHEETS
Cash and cash equivalents	188,182	103,797
Restricted cash	251	1,304
Total cash, cash equivalents and restricted cash	188,433	105,101
SUPPLEMENTAL DISCLOSURES OF OTHER CASH FLOW INFORMATION:
Cash paid for income taxes	1,221	829
Cash paid for interest	7,671	49
Capitalized assets financed by accounts payable and accrued expenses	1,513	2,388
Capitalized stock-based compensation	956	616
Operating lease right-of-use assets obtained in exchange for new operating lease liabilities	22,651	2,036
Purchase consideration - indemnification claims holdback	1,409	0
Common stock and options issued for mergers and acquisitions	495,591	287,418
Debt discount, non-cash	$ 10,800	$ 0

Organization and Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Organization and Summary of Significant Accounting Policies	Organization and Summary of Significant Accounting Policies Company Overview Magnite, Inc. ("Magnite" or the "Company"), formerly known as The Rubicon Project, Inc., was formed in Delaware and began operations in April 2007. On April 1, 2020, Magnite completed a stock-for-stock merger with Telaria, Inc. ("Telaria" and such merger the "Telaria Merger"), a leading sell side advertising platform and provider of connected television ("CTV") technology. On April 30, 2021, the Company completed its acquisition of SpotX, Inc. ("SpotX" and such acquisition the "SpotX Acquisition"), a leading CTV and video advertising platform. On July 1, 2021, the Company completed its acquisition of SpringServe, LLC ("SpringServe" and such acquisition the "SpringServe Acquisition"), a leading ad serving platform for CTV. The Company operates a sell side advertising platform that offers buyers and sellers of digital advertising a single partner for transacting globally across all channels, formats, and auction types. The Company provides a technology solution to automate the purchase and sale of digital advertising inventory. The Company’s platform features applications and services for sellers of digital advertising inventory, or publishers, that own or operate websites, applications, CTV channels, and other digital media properties, to manage and monetize their inventory; applications and services for buyers, including advertisers, agencies, agency trading desks, and demand side platforms, to buy digital advertising inventory; and a transparent, independent marketplace that brings buyers and sellers together and facilitates intelligent decision making and automated transaction execution at scale. The Company's clients include many of the world's leading sellers and buyers of digital advertising inventory. Basis of Presentation and Summary of Significant Accounting Policies The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with United States Generally Accepted Accounting Principles, or GAAP, for interim financial information and the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring adjustments) considered necessary for a fair statement of the results for the interim period presented have been included. Operating results for the three and nine months ended September 30, 2021 are not necessarily indicative of the results that may be expected for any future interim period, the year ending December 31, 2021, or for any future year. The condensed consolidated balance sheet at December 31, 2020 has been derived from the audited financial statements at that date, but does not include all of the disclosures required by GAAP. The accompanying condensed consolidated financial statements should be read in conjunction with the Company's audited consolidated financial statements and notes thereto for the year ended December 31, 2020 included in its 2020 Annual Report on Form 10-K. Aside from the adoption of ASU 2020-06, as described below, there have been no significant changes in the Company's accounting policies from those disclosed in its audited consolidated financial statements and notes thereto for the year ended December 31, 2020 included in its Annual Report on Form 10-K. Use of Estimates The preparation of condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported and disclosed financial statements and accompanying footnotes. Due to the economic uncertainty as a result of the COVID-19 pandemic, it has become more difficult to apply certain assumptions and judgments into these estimates. The extent of the impact of COVID-19 pandemic on the Company's operational and financial performance will depend on future developments, which are highly uncertain and cannot be predicted, including but not limited to, the duration and spread of the pandemic, its severity, including any resurgence, the actions to contain the virus or treat its impact, and how quickly and to what extent normal economic and operating conditions can resume. During the nine months ended September 30, 2021, this uncertainty continued to result in a higher level of judgment related to its estimates and assumptions. As of the date of issuance of the condensed consolidated financial statements for the three and nine months ended September 30, 2021, the Company is not aware of any specific event or circumstance that would require the Company to update its estimates, judgments, or revise the carrying value of its assets or liabilities. These estimates may change, as new events occur and additional information is obtained, and are recognized in the consolidated financial statements as soon as they become known. Actual results could differ materially from these estimates. Recently Adopted Accounting Standards On January 1, 2021, the Company adopted ASU 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity's Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity (ASU "2020-06") on a prospective basis, which simplifies the accounting for convertible instruments by reducing the number of accounting models available for convertible debt instruments that require separating embedded conversion features from convertible instruments. This guidance also eliminates the treasury stock method to calculate diluted earnings per share for convertible instruments and requires the use of the if-converted method. The adoption of this standard is included in the financial statements as of September 30, 2021 and for the three and nine months ended September 30, 2021 and September 30, 2020, respectively. Refer to Note 14—"Convertible Senior Notes" for additional information related to accounting for convertible debt issued during the nine months ended September 30, 2021. On January 1, 2021, the Company adopted ASU 2019-12—Simplifying the Accounting for Income Taxes ("ASU 2019-12"). ASU 2019-12 simplifies the accounting for income taxes by removing certain exceptions to general principles in Topic 740 and clarifies and amends existing guidance for clarity and consistent application. There was no material impact to the quarterly or year to date income tax provision. Recent Accounting Pronouncements In March 2020, the FASB issued Update No. 2020-04, Reference Rate Reform (Topic 848), which provides temporary optional guidance to companies impacted by the transition away from the LIBOR. The amendment provides certain expedients and exceptions to applying GAAP in order to lessen the potential accounting burden when contracts, hedging relationships, and other transactions that reference LIBOR as a benchmark rate are modified. Further, in January 2021, the FASB issued Update No. 2021-01, Reference Rate Reform (Topic 848), which clarifies the scope of Topic 848 so that derivatives affected by the discounting transition are explicitly eligible for certain optional expedients and exceptions in Topic 848. These amendments are effective upon issuance and expire on December 31, 2022. The Company is currently assessing the impact of the LIBOR transition on the Company's condensed consolidated financial statements. In July 2021, the FASB issued Update No. 2021-05, Leases (Topic 842)—Lessors – Certain Leases with Variable Lease Payments ("ASU 2021-05"). ASU 2021-05 requires a lessor to classify a lease with variable lease payments that do not depend on an index or rate as an operating lease if specified criteria are met. This guidance will be effective on January 1, 2022, either retrospectively to leases that commenced or were modified on or after our adoption of ASU 2016-02 on January 1, 2019, or on a prospective basis, with early adoption permitted. The Company is currently assessing the impact of the new guidance on the Company's condensed consolidated financial statements. The Company does not believe there are any other recently issued and effective or not yet effective pronouncements that would have or are expected to have any significant effect on the Company’s financial position, cash flows or results of operations.

Net Loss Per Share

9 Months Ended

Sep. 30, 2021

Earnings Per Share [Abstract]

Net Loss Per Share

The following table presents the basic and diluted net loss per share:


	Three Months Ended				Nine Months Ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
	(in thousands, except per share data)
Basic and Diluted Income (Loss) Per Share:
Net loss	$	(24,319)	$	(10,515)	$	(388)	$	(59,318)
Weighted-average common shares outstanding	131,501		110,416		124,325		91,371


Weighted-average common shares outstanding used to compute net loss per share	131,501		110,416		124,325		91,371
Basic and diluted net loss per share	$	(0.18)	$	(0.10)	$	—	$	(0.65)

The following weighted-average shares have been excluded from the calculation of diluted net loss per share attributable to common stockholders for each period presented because they are anti-dilutive:


	Three Months Ended		Nine Months Ended
	September 30, 2021	September 30, 2020	September 30, 2021	September 30, 2020
	(in thousands)		(in thousands)
Options to purchase common stock	4,116	1,920	4,712	1,720

Unvested restricted stock units	4,253	3,768	5,876	3,851
Unvested performance stock units	195	14	196	6
ESPP	11	30	49	40
Convertible Senior Notes	6,262	—	4,499	—
Total shares excluded from net loss per share	14,837	5,732	15,332	5,617

For the three and nine months ended September 30, 2021, diluted shares used to compute diluted earnings per share included outstanding performance stock units granted during April 2020, April 2021, and August 2021 based on a current achievement level of 150%, 0%, and 0%, respectively. Refer to Note 9—"Stock-Based Compensation" for additional information related to performance stock units.For the three and nine months ended September 30, 2021, diluted shares used to compute diluted earnings per share excluded the shares that would be issuable assuming conversion of all of the Convertible Senior Notes (as defined in Note 14) because they are anti-dilutive. Diluted earnings per share for the Convertible Senior Notes is calculated under the if-converted method in accordance with ASC 260, Earnings Per Share. The Convertible Senior Notes have an initial conversion rate of 15.6539 shares of common stock per $1,000 principal amount of the Convertible Senior Notes, which will be subject to anti-dilution adjustments in certain circumstances. As of September 30, 2021, the number of shares that would be issuable assuming conversion of all of the Convertible Senior Notes is approximately 6,261,560. Refer to Note 14—"Convertible Senior Notes" for additional information related to accounting for Convertible Senior Notes issued and associated Capped Call Transactions

Revenue

9 Months Ended

Sep. 30, 2021

Revenue from Contract with Customer [Abstract]

Revenue

For the majority of transactions on the Company's platform, the Company reports revenue on a net basis as it does not act as the principal in the purchase and sale of digital advertising inventory because it does not have control of the digital advertising inventory and does not set prices agreed upon within the auction marketplace. For certain advertising campaigns that are transacted through insertion orders, the Company reports revenue on a gross basis, based primarily on its determination that the Company acts as the primary obligor in the delivery of advertising campaigns for buyers with respect to such transactions.

For periods prior to the SpotX Acquisition, revenue reported on a gross basis was generally less than 3% of the Company's total revenue. As a result of the SpotX Acquisition, an increased percentage of the Company's revenue is reported on a gross basis. The following table presents our revenue recognized on a net basis and on a gross basis for the three and nine months ended September 30, 2021 and September 30, 2020, respectively.


	Three Months Ended								Nine Months Ended
	September 30, 2021				September 30, 2020				September 30, 2021				September 30, 2020
	(in thousands, except percentages)
Revenue:
Net basis	$	105,866	80	%	$	59,913	98	%	$	258,236	84	%	$	138,063	99	%
Gross basis	26,005		20		1,069		2		48,891		16		1,562		1
Total	$	131,871	100	%	$	60,982	100	%	$	307,127	100	%	$	139,625	100	%

The following table presents our revenue by channel for the three and nine months ended September 30, 2021 and 2020:


	Three Months Ended								Nine Months Ended
	September 30, 2021				September 30, 2020				September 30, 2021				September 30, 2020
	(in thousands, except percentages)
Channel:
CTV	$	57,885	44	%	$	11,059	18	%	$	115,040	38	%	$	18,978	14	%
Desktop	30,573		23		20,901		34		80,166		26		51,468		37
Mobile	43,413		33		29,022		48		111,921		36		69,179		49
Total	$	131,871	100	%	$	60,982	100	%	$	307,127	100	%	$	139,625	100	%

The following table presents the Company's revenue disaggregated by geographic location, based on the location of the Company's sellers:


	Three Months Ended				Nine Months Ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
	(in thousands)				(in thousands)
United States	$	104,633	$	45,048	$	237,844	$	101,168

International	27,238		15,934		69,283		38,457
Total	$	131,871	$	60,982	$	307,127	$	139,625

Payment terms are specified in agreements between the Company and the buyers and sellers on its platform. The Company generally bills buyers at the end of each month for the full purchase price of impressions filled in that month. The Company recognizes volume discounts as a reduction of revenue as they are incurred. Specific payment terms may vary by agreement, but are generally seventy-five days or less. The Company's accounts receivable are recorded at the amount of gross billings to buyers, net of allowances for the amounts the Company is responsible to collect. The Company's accounts payable related to amounts due to sellers are recorded at the net amount payable to sellers (see Note 5). Accordingly, both accounts receivable and accounts payable appear large in relation to revenue reported on a net basis.

Accounts receivable are recorded at the invoiced amount, are unsecured, and do not bear interest. The allowance for doubtful accounts is reviewed quarterly, requires judgment, and is based on the best estimate of the amount of probable credit losses in existing accounts receivable. The Company reviews the status of the then-outstanding accounts receivable on a customer-by-customer basis, taking into consideration the aging schedule of receivables, its historical collection experience, current information regarding the client, subsequent collection history, and other relevant data, in establishing the allowance for doubtful accounts. Accounts receivable is presented net of an allowance for doubtful accounts of $4.0 million at September 30, 2021, and $2.4 million at December 31, 2020. Accounts receivable are written off against the allowance for doubtful accounts when the Company determines amounts are no longer collectible.

The Company reviews the associated payable to sellers for recovery of buyer receivable allowance and write-offs; in some cases, the Company can reduce the payable to sellers. The reduction of seller payables related to recovery of uncollected buyer receivables is netted against allowance expense. The contra seller payables related to recoveries were $2.2 million and $1.5 million as of September 30, 2021 and December 31, 2020, respectively.

The following is a summary of activity in the allowance for doubtful accounts for the three and nine months ended September 30, 2021 and 2020:


	Three Months Ended				Nine Months Ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
	(in thousands)				(in thousands)
Allowance for doubtful accounts, Beginning Balance	$	3,279	$	4,672	$	2,360	$	3,400
Allowance for doubtful accounts, merger and acquisition-assumed	425		—		835		1,033
Write-offs	(14)		(1)		(35)		(1,897)
Increase (decrease) in provision for expected credit losses	342		(274)		852		1,854
Recoveries of previous write-offs	—		83		20		90
Allowance for doubtful accounts, September 30	$	4,032	$	4,480	$	4,032	$	4,480

During the three and nine months ended September 30, 2021, the provision for expected credit losses associated with accounts receivable increased by $0.3 million and $0.9 million was offset by decreases of contra seller payables related to recoveries of uncollected buyer receivables of an immaterial amount and $0.6 million, which resulted in $0.4 million and $0.2 million, respectively, of bad debt recoveries. During the three and nine months ended September 30, 2020, the provision for expected credit losses associated with accounts receivable of $(0.3) million and $1.9 million was offset by increases of contra seller payables related to recoveries of uncollected buyer receivables of $(0.3) million and $1.8 million, respectively, which resulted in an immaterial amount of bad debt expense during the period.

- Definition

The entire disclosure of revenue from contract with customer to transfer good or service and to transfer nonfinancial asset. Includes, but is not limited to, disaggregation of revenue, credit loss recognized from contract with customer, judgment and change in judgment related to contract with customer, and asset recognized from cost incurred to obtain or fulfill contract with customer. Excludes insurance and lease contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-URI http://asc.fasb.org/topic&trid=49130388

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130551-203045

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130556-203045

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130550-203045

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130558-203045

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

+ Details

Fair Value Measurements

9 Months Ended

Sep. 30, 2021

Fair Value Disclosures [Abstract]

Fair Value Measurements

Recurring Fair Value Measurements

Fair value represents the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Observable inputs are based on market data obtained from independent sources. The fair value hierarchy is based on the following three levels of inputs, of which the first two are considered observable and the last one is considered unobservable:

•Level 1 – Quoted prices (unadjusted) in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date.

•Level 2 – Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly.

•Level 3 – Unobservable inputs.

The table below sets forth a summary of financial instruments that are measured at fair value on a recurring basis at September 30, 2021:


	Total		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(in thousands)
Cash equivalents	$	7,869	$	7,869	$	—	$	—

The table below sets forth a summary of financial instruments that are measured at fair value on a recurring basis at December 31, 2020:


	Total		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(in thousands)
Cash equivalents	$	7,868	$	7,868	$	—	$	—

At September 30, 2021 and December 31, 2020, cash equivalents of $7.9 million and $7.9 million, respectively, consisted of money market funds and commercial paper, with original maturities of three months or less. The carrying amounts of cash equivalents are classified as Level 1 or Level 2 depending on whether or not their fair values are based on quoted market prices for identical securities that are traded in an active market.

At September 30, 2021, the Company had Convertible Senior Notes (as defined in Note 14) included in its balance sheet. The estimated fair value of the Company's Convertible Senior Notes was $341.0 million as of September 30, 2021. The estimated fair value of Convertible Senior Notes is based on market rates and the closing trading price of the Convertible Senior Notes as of September 30, 2021 and is classified as Level 2 in the fair value hierarchy.

There were no transfers between Level 1 and Level 2 fair value measurements during the nine months ended September 30, 2021 and the year ended December 31, 2020.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Other Balance Sheet Amounts

9 Months Ended

Sep. 30, 2021

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Other Balance Sheet Amounts

Accounts payable and accrued expenses included the following:


	September 30, 2021		December 31, 2020
	(in thousands)
Accounts payable—seller	$	791,227	$	492,605
Accounts payable—trade	15,321		4,268
Accrued employee-related payables	20,544		12,442
Accrued holdback - indemnification claims	1,409		—
Total	$	828,501	$	509,315

Restricted cash was $0.3 million and $0.1 million at September 30, 2021 and December 31, 2020, respectively, which was included within other assets, non-current.

Goodwill, Intangible Assets, and Capitalized Costs Incurred in Cloud Computing Arrangements

9 Months Ended

Sep. 30, 2021

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill, Intangible Assets, and Capitalized Costs Incurred in Cloud Computing Arrangements

The Company's goodwill balance as of September 30, 2021 and December 31, 2020 was $972.7 million and $158.1 million, respectively. The increase during the nine months ended September 30, 2021 was a result of the SpotX and SpringServe Acquisitions (see Note 7).

The Company’s intangible assets as of September 30, 2021 and December 31, 2020 included the following:


	September 30, 2021		December 31, 2020
	(in thousands)
Amortizable intangible assets:
Developed technology	$	373,558	$	77,658
Customer relationships	173,950		37,950
In-process research and development	14,630		8,030
Backlog	11,100		—
Non-compete agreements	2,070		70
Trademarks	1,400		—
Total identifiable intangible assets, gross	576,708		123,708
Accumulated amortization—intangible assets:
Developed technology	(57,282)		(21,905)
Customer relationships	(47,359)		(11,877)
In-process research and development	(449)		—
Backlog	(6,938)		—
Non-compete agreements	(756)		(42)
Trademarks	(353)		—
Total accumulated amortization—intangible assets	(113,137)		(33,824)
Total identifiable intangible assets, net	$	463,571	$	89,884

Amortization of intangible assets for the three months ended September 30, 2021 and 2020 was $42.2 million and $7.8 million, respectively, and $79.3 million and $16.9 million for the nine months ended September 30, 2021 and 2020, respectively.

The estimated remaining amortization expense associated with the Company's intangible assets was as follows as of September 30, 2021:


Fiscal Year	Amount
	(in thousands)
Remaining 2021	$	42,527
2022	147,361
2023	101,996
2024	84,218
2025	66,668
Thereafter	20,801
Total	$	463,571

During the three and nine months ended September 30, 2021, the Company capitalized $0.1 million and $0.7 million, respectively, related to cloud computing arrangements. These costs are related to arrangements for infrastructure as a service, platform as a service, and software as a service. Capitalized costs associated with these arrangements as of September 30, 2021 and December 31, 2020 are included within prepaid expenses and other current assets and other assets, non-current within the condensed consolidated balance sheet in the amounts of $0.5 million and $0.7 million, and $0.2 million and $0.7 million, respectively. The amortization of these agreements was $0.1 million and $0.3 million for the three and nine months ended September 30, 2021, respectively.

Business Combinations

9 Months Ended

Sep. 30, 2021

Business Combination and Asset Acquisition [Abstract]

Business Combinations

2020 Merger—Telaria

On April 1, 2020, the Company completed the Telaria Merger. Management's purchase price allocation was finalized as of March 31, 2021, resulting in no changes from the purchase price allocation as of December 31, 2020.

Unaudited Pro Forma Information

The following table provides unaudited pro forma information as if Telaria had been merged with the Company as of January 1, 2019. The unaudited pro forma information reflects adjustments for additional amortization resulting from the fair value

adjustments to assets acquired and liabilities assumed, adjustments for alignment of accounting policies, and transaction expenses as if the Telaria Merger occurred on January 1, 2019. The pro forma results do not include any anticipated cost synergies or other effects of the integration for the merged companies. Accordingly, pro forma amounts are not necessarily indicative of the results that actually would have occurred had the acquisition been completed on the dates indicated, nor is it indicative of the future operating results of the combined company.


	Nine Months Ended
		September 30, 2020
	(in thousands)
Pro Forma Revenue		$	154,663
Pro Forma Net Loss		$	(69,706)

2021 Acquisition—SpotX

On April 30, 2021, the Company completed the SpotX Acquisition, pursuant to a Stock Purchase Agreement, dated as of February 4, 2021 (the "Purchase Agreement"), by and between the Company and RTL US Holdings, Inc. ("RTL"). The initial purchase price for the SpotX Acquisition was $560 million in cash ("Cash Consideration") and 14,000,000 shares of the Company's common stock. Per the terms of the Purchase Agreement, at the completion of the Company’s offering of its Convertible Senior Notes, RTL elected to increase the Cash Consideration by an amount equal to 20% of the gross proceeds of the Convertible Senior Notes (which amount was equal to $80 million) and to reduce the number of shares of common stock it would otherwise receive by a number of shares of common stock equal to 20% of the gross proceeds of the proposed offering of notes ($80 million) divided by the closing price of a share of our common stock on the trading day immediately prior to the date of pricing of the proposed offering of notes ($49.21). As a result of this election, the adjusted purchase price was $1.1 billion, prior to customary working capital adjustments and other adjustments, consisting of $640 million in cash plus 12,374,315 shares of common stock (based on the fair value of the Company's common stock on April 30, 2021). The Cash Consideration is subject to customary working capital and other adjustments. The working capital was approximately $65.2 million, including cash balances acquired and other working capital adjustments, resulting in a total purchase price of $1.2 billion. The Company financed the Cash Consideration through borrowings under the Term Loan B Facility (Note 15) and the Convertible Senior Notes (Note 14).

In accordance with ASC 805, the Company recorded the acquisition based on the fair value of the consideration transferred and then allocated the purchase price to the identifiable assets acquired and liabilities assumed based on their respective fair values as of the acquisition date. The excess of the value of consideration transferred over the aggregate fair value of those net assets was recorded as goodwill. Any identified definite lived intangible assets will be amortized over their estimated useful lives and any identified intangible assets with indefinite useful lives and goodwill will not be amortized but will be tested for impairment at least annually. All intangible assets and goodwill will be tested for impairment when certain indicators are present. Determining the fair value of assets acquired and liabilities assumed requires management to use significant judgment and estimates including the selection of valuation methodologies, estimates of future revenues and cash flows, discount rates, and selection of comparable companies.

Management's purchase price allocation is preliminary and subject to change pending finalization of the valuation, including finalization of tax attributes and tax related liabilities. Under the acquisition method of accounting for business combinations, if the Company identifies changes to acquired deferred tax asset ("DTA") valuation allowances or liabilities related to uncertain tax positions during the measurement period, and they are related to new information obtained about facts and circumstances that existed as of the acquisition date, those changes are considered a measurement-period adjustment, and the Company will record the offset to goodwill. The Company records all other changes to DTA valuation allowances and liabilities related to uncertain tax positions in current- period income tax expense.

For purposes of measuring the estimated fair value, where applicable, of the assets acquired and the liabilities assumed as reflected in the unaudited condensed combined financial information, the Company has applied the guidance in ASC 820, Fair Value Measurement, which establishes a framework for measuring fair value. In accordance with ASC 820, fair value is an exit price and is defined as "the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date." Under ASC 805, acquisition-related transaction costs and acquisition-related restructuring charges are not included as components of consideration transferred but are accounted for as expenses in the period in which the costs are incurred.

The following table summarizes the total purchase consideration (in thousands):


Cash Consideration	$	640,000
Stock Consideration (Fair Value of Shares of Magnite common stock)	495,591
Working capital adjustment	65,152
Total purchase consideration	$	1,200,743

The purchase consideration for the SpotX Acquisition included 12,374,315 shares of the Company's common stock with a fair value of approximately $495.6 million, based on the close price of the Company's common stock at closing on April 30, 2021, which was $40.05 per share, and working capital adjustment of $65.2 million, mainly consisting of cash balances acquired on the date of the SpotX Acquisition and other opening balance sheet adjustments.

The fair value of the purchase price was allocated to the identifiable assets acquired and liabilities assumed based upon their estimated fair values as of the date of the SpotX Acquisition as set forth below:


Cash	$	81,967
Restricted cash	199
Accounts receivable	199,649
Prepaid and other assets, current	12,308
Fixed assets	5,093
Intangible assets	429,600
Right-of-use lease asset	11,785
Goodwill	790,466

Total assets to be acquired	1,531,067
Accounts payable and accrued expenses	205,913

Other current liabilities	7,169
Lease liabilities	12,625
Deferred tax liability, net	104,617
Total liabilities to be assumed	330,324
Total purchase price	$	1,200,743

The Company believes the amount of goodwill resulting from the purchase price allocation is primarily attributable to expected synergies from the assembled workforce, an increase in development capabilities, increased offerings to customers, and enhanced opportunities for growth and innovation. Goodwill will not be amortized but instead will be tested for impairment at least annually or more frequently if certain indicators of impairment are present. In the event that goodwill has become impaired, the Company will record an expense for the amount impaired during the quarter in which the determination is made. The acquired intangibles and goodwill resulting from the SpotX Acquisition are not amortizable for tax purposes.

The following table summarizes the components of the intangible assets and estimated useful lives as of the date of the SpotX Acquisition (dollars in thousands):


			Estimated Useful Life
Technology	$	280,400	5 years
Customer relationships	130,300		2 to 4 years
Backlog	11,100		<1 year
In-process research and development	5,800		3 years*
Non-compete agreements	1,500		1 year
Trademarks	500		<1 year
Total intangible assets acquired	$	429,600
* In-process research and development consists of six projects with a weighted-average useful life of 3.0 years. Amortization begins once associated projects are completed and it is determined the projects have alternative future use.

The fair value of the acquired technology and in-process research and development was valued using the Excess Earnings Method. This methodology included allocating future revenue projections to the existing technologies and applying decay rates and appropriate discount rates that reflect the respective intangible asset's relative risk profile when compared to other intangible assets as well as the discount rate for the overall business.

The Company used the Loss‐of‐Revenue and Income Method in its valuation of the existing customer relationships and non-compete agreements. To the extent that future cash flows of the business would be negatively affected in the absence of these relationships and non-compete agreements, they would be deemed to have economic value. This method attempts to quantify the scenario whereby the owner loses the right to the intangible asset and the resulting losses of revenue and income. Under this analysis, the value of the cash flows with the intangible asset is compared to the value of the cash flows without the intangible asset and the difference represents the value of the intangible asset. This methodology included applying a discount rate and the expected timing it would take to further enhance customer relationships.

The fair value of the backlog was based on the Excess Earnings Method, taking into consideration the existing contracts as of the date of the SpotX Acquisition and the respective cost to complete the servicing of the existing agreements. The resulting stream of after tax earnings were discounted to present value by applying an appropriate discount rate for the asset. The discount rate was selected based on the intangible asset’s relative risk profile when compared to the other intangible assets as well as the discount rate for the overall business.

The fair value of the trademarks was based on the Income Approach, specifically the Relief‐from‐Royalty Method. Under this method, data is obtained regarding actual royalty payments made for similar intangible assets. After the appropriate royalty rate is determined, the reasonable royalty savings is then discounted to its present value over the remaining technological, economic, or legal life of the intangible asset.

Intangible assets are generally amortized on a straight-line basis, which approximates the pattern in which the economic benefits are consumed, over their estimated useful lives. Amortization of developed technology is included in cost of revenues and the amortization of customer relationships, backlog, non-compete agreements, and trademarks is included in sales and marketing expenses in the condensed consolidated statement of operations. Once the projects associated with acquired in-process research and development are completed, amortization will be included in cost of revenues in the condensed consolidated statement of operations. The intangible assets generated in the SpotX Acquisition are not tax deductible.

In connection with the SpotX Acquisition, the Company recorded deferred tax liabilities related to definite-lived intangible assets that were acquired of $113.0 million. As a result of this deferred tax liability balance, the Company reduced its deferred tax asset valuation allowance by $56.2 million. Such reduction was recognized as an income tax benefit in the condensed consolidated statement of operations for the nine months ended September 30, 2021. The deferred tax liability was calculated based on an estimated combined tax rate of 26.3%.

The Company recognized approximately $0.8 million and $27.9 million of acquisition related costs included in the "Merger, acquisition, and restructuring costs" in the Company's condensed consolidated statement of operations during the three and nine months ended September 30, 2021 related to the SpotX Acquisition.

2021 Acquisition—SpringServe

On July 1, 2021, the Company completed the acquisition of ServeMotion, Inc., a Delaware corporation (including its wholly owned subsidiary, SpringServe, LLC, "SpringServe"), through the Company's wholly-owned subsidiary, SpotX, pursuant to a definitive agreement entered into on July 1, 2021. As a result of the SpringServe Acquisition, SpringServe has become a wholly-owned subsidiary of SpotX, and a wholly-owned indirect subsidiary of the Company.

The following table summarizes the total estimated purchase consideration (in thousands):


Cash Consideration	$	31,136
SpotX initial cash investment in SpringServe	2,075
Fair value appreciation of SpotX purchase right	7,450
Indemnification claims - holdback	1,409
Total purchase consideration	$	42,070

In 2020, SpotX made a minority investment of $2.1 million in SpringServe in conjunction with a strategic partnership agreement between the two companies, which included an option agreement to purchase SpringServe. At the time of Magnite's acquisition of SpotX, the fair value of SpotX's minority investment and purchase right were valued at a combined $7.5 million for a total minority investment and purchase right of $9.5 million . In connection with the SpringServe Acquisition, approximately $1.4 million of the purchase price was held back to cover possible indemnification claims, which is expected to be paid in cash one year after the acquisition.

Management's purchase price allocation is preliminary and subject to change pending finalization of the valuation, including finalization of tax attributes and tax related liabilities. Under the acquisition method of accounting for business combinations, if the Company identifies changes to acquired DTA valuation allowances or liabilities related to uncertain tax positions during the measurement period, and they are related to new information obtained about facts and circumstances that existed as of the acquisition date, those changes are considered a measurement-period adjustment, and the Company will record the offset to goodwill. The Company records all other changes to DTA valuation allowances and liabilities related to uncertain tax positions in current- period income tax expense.

The fair value of the purchase price was allocated to the identifiable assets acquired and liabilities assumed based upon their estimated fair values as of the date of the SpringServe Acquisition as set forth below:


Cash	$	1,062
Accounts receivable	3,234
Prepaid and other assets, current	157
Fixed assets	25
Intangible assets	23,400
Right-of-use lease asset	1,879
Goodwill	24,156

Total assets to be acquired	53,913
Accounts payable and accrued expenses	2,475
Other current liabilities	35
Lease liabilities	3,179
Deferred tax liability, net	6,154
Total liabilities to be assumed	11,843
Total preliminary purchase price	$	42,070

The following table summarizes the components of the intangible assets and estimated useful lives as of the date of the SpringServe Acquisition (dollars in thousands):


			Estimated Useful Life
Technology	$	15,500	5 years
Customer relationships	5,700		2 years
Trademarks and Trade Names	900		3 years
In-process research and development	800		3 years*
Non-compete agreements	500		2 years
Total intangible assets acquired	$	23,400
* In-process research and development consists of two projects with a weighted-average useful life of 3 years. Amortization begins once associated projects are completed and it is determined the projects have alternative future use.

Intangible assets are generally amortized on a straight-line basis, which approximates the pattern in which the economic benefits are consumed, over their estimated useful lives. Amortization of developed technology is included in cost of revenues and the amortization of customer relationships, non-compete agreements, and trademarks is included in sales and marketing expenses in the condensed consolidated statement of operations. Once the projects associated with acquired in-process research and development are completed, amortization will be included in cost of revenues in the condensed consolidated statement of operations. The acquired intangibles and goodwill resulting from the SpringServe Acquisition are not tax deductible.

In connection with the SpringServe Acquisition, the Company recorded deferred tax liabilities related to definite-lived intangible assets that were acquired of $6.2 million. As a result of this and the SpotX deferred tax liability balance, the Company recognized an income tax benefit in the condensed consolidated statement of operations for the nine months ended September 30, 2021. The deferred tax liability was calculated based on an estimated combined tax rate of 26.3%.

SpringServe Acquisition related costs included in the "Merger, acquisition, and restructuring costs" in the Company's condensed consolidated statement of operations during the three and nine months ended September 30, 2021 were immaterial.

Unaudited Pro Forma Information

The following table provides unaudited pro forma information as if the SpotX and SpringServe Acquisitions had been acquired by the Company as of January 1, 2020. The unaudited pro forma information reflects adjustments for additional amortization resulting from the fair value adjustments to assets acquired and liabilities assumed, adjustments for alignment of accounting policies, and transaction expenses as if the SpotX and SpringServe Acquisitions occurred on January 1, 2020. The pro forma results do not include any anticipated cost synergies or other effects of the combined companies. Accordingly, pro forma

amounts are not necessarily indicative of the results that actually would have occurred had the SpotX and SpringServe Acquisitions been completed on the dates indicated, nor is it indicative of the future operating results of the combined company.


	Three Months Ended			Nine Months Ended
		September 30, 2020		September 30, 2021		September 30, 2020
		(in thousands)
Pro Forma Revenue		$	104,249	$	379,180	$	243,781
Pro Forma Net Income (Loss)		$	(29,651)	$	(88,187)	$	(157,803)

During the three and nine months ended September 30, 2021, due to the process of integrating the operations of SpotX into the operations of the Company, the determination of SpotX's post-acquisition revenue and operating results on a standalone basis was impracticable. The SpringServe post-acquisition revenue and operating results on a standalone basis were immaterial.

Merger, Acquisition, and Restructuring Costs

9 Months Ended

Sep. 30, 2021

Restructuring and Related Activities [Abstract]

Merger, Acquisition, and Restructuring Costs

Merger, acquisition, and restructuring costs consist primarily of professional services fees and employee termination costs, including stock-based compensation charges, associated with the Telaria Merger, the SpotX Acquisition, and restructuring activities.

The following table summarizes merger, acquisition, and restructuring cost activity (in thousands):


	Three Months Ended				Nine Months Ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
	(in thousands)
Professional services (investment banking advisory, legal and other professional services)	$	1,064	$	952	$	28,032	$	9,533
Personnel related (severance and one-time termination benefit costs)	1,312		948		6,176		5,590
Non-cash stock-based compensation (double-trigger acceleration and severance)	48		354		1,070		1,554
Loss contracts (lease related)	—		—		2,500		—
Total merger, acquisition, and restructuring costs	$	2,424	$	2,254	$	37,778	$	16,677

Accrued merger, acquisition, and restructuring costs were $4.1 million and $2.9 million at September 30, 2021 and December 31, 2020, respectively, and were primarily related to the SpotX Acquisition, the SpringServe Acquisition, and the Telaria Merger. Accrued restructuring costs associated with personnel costs are included within accounts payable and accrued expenses and accruals related to the assumed loss contracts are included within other current liabilities and other liabilities, non-current on the Company's condensed consolidated balance sheet.


	(in thousands)
Accrued merger, acquisition, and restructuring costs at December 31, 2020	$	2,935
Restructuring costs, personnel related and non-cash stock-based compensation	7,246
Restructuring activity, merger and acquisition loss contracts	2,500
Cash paid for restructuring costs	(5,035)
Non-cash loss contracts (lease related)	(2,500)
Non-cash stock-based compensation	(1,070)
Accrued merger, acquisition, and restructuring costs at September 30, 2021	$	4,076

Stock-Based Compensation

9 Months Ended

Sep. 30, 2021

Share-based Payment Arrangement [Abstract]

Stock-Based Compensation

Stock-Based CompensationThe Company’s equity incentive plans provide for the grant of equity awards, including non-statutory or incentive stock options, restricted stock awards ("RSAs"), and restricted stock units ("RSUs"), to the Company's employees, officers, directors, and consultants. The Company's board of directors administers the plans. Options outstanding vest based upon continued service at

varying rates, but generally over four years from issuance with 25% vesting after one year of service and the remainder vesting monthly thereafter. RSAs and RSUs vest at varying rates, typically approximately 25% vesting after approximately one year of service and the remainder vesting annually, semi-annually, or quarterly thereafter. The restricted stock units granted in 2021 included 0.3 million that vest 50% on each of the first and second anniversaries of the grant date. Options, RSAs, and RSUs granted under the plans accelerate under certain circumstances for certain participants upon a change in control, as defined in the governing plan or award agreement, and termination of employment. An aggregate of 12,968,404 shares remained available for future grants at September 30, 2021 under the plans.

Stock Options

A summary of stock option activity for the nine months ended September 30, 2021 is as follows:


	Shares Under Option	Weighted- Average Exercise Price		Weighted- Average Contractual Life	Aggregate Intrinsic Value
	(in thousands)				(in thousands)
Outstanding at December 31, 2020	6,695	$	5.61
Granted	302	$	38.99
Exercised	(1,393)	$	6.28

Forfeited	(306)	$	8.87
Outstanding at September 30, 2021	5,298	$	7.15	5.79 years	$	113,430
Exercisable at September 30, 2021	3,768	$	5.51	4.82 years	$	84,758

The total intrinsic value of options exercised during the nine months ended September 30, 2021 was $43.4 million. At September 30, 2021, the Company had unrecognized employee stock-based compensation expense relating to nonvested stock options of approximately $9.6 million, which is expected to be recognized over a weighted-average period of 2.2 years. Total fair value of options vested during the nine months ended September 30, 2021 was $3.3 million.

The Company estimates the fair value of stock options that contain service and/or performance conditions using the Black-Scholes option pricing model. The grant date fair value of options granted during the nine months ended September 30, 2021 was $24.57 per share. The weighted-average input assumptions used by the Company were as follows:


	Three Months Ended				Nine Months Ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
Expected term (in years)	5.0		6.3		5.0		6.3
Risk-free interest rate	0.90	%	0.33	%	0.88	%	0.45	%
Expected volatility	79	%	68	%	79	%	67	%
Dividend yield	—	%	—	%	—	%	—	%

Restricted Stock Units

A summary of restricted stock unit activity for the nine months ended September 30, 2021 is as follows:


	Number of Shares		Weighted-Average Grant Date Fair Value
	(in thousands)
Restricted stock units outstanding at December 31, 2020	9,286		$	5.30
Granted	2,816		$	38.54
Canceled	(779)		$	12.17
Vested and released	(3,873)		$	5.21
Restricted stock units outstanding at September 30, 2021	7,450		$	17.19
Restricted stock units outstanding and unvested*	7,413	*	$	17.24
*At September 30, 2021, outstanding restricted stock units included 37,318 units that were vested but deferred.

The weighted-average grant date fair value per share of restricted stock units granted during the nine months ended September 30, 2021 was $38.54. The aggregate fair value of restricted stock units that vested during the nine months ended September 30, 2021 was $126.1 million. At September 30, 2021, the intrinsic value of nonvested restricted stock units was $208.6 million. At September 30, 2021, the Company had unrecognized stock-based compensation expense relating to unvested restricted stock units of approximately $112.0 million, which is expected to be recognized over a weighted-average period of 2.5 years.

Performance Stock Units

In April 2020 and April 2021, the Company granted the Company's CEO 146,341 and 26,291 restricted stock units that vest based on certain stock price performance metrics with a fair value of $0.9 million and $1.4 million, respectively. The grant date fair value per share of restricted stock was $6.15 and $52.49, respectively, which was estimated using a Monte-Carlo lattice model. At September 30, 2021, the Company had unrecognized employee stock-based compensation expense for the April 2020 and April 2021 grants of approximately $0.5 million and $1.2 million, which is expected to be recognized over the remaining 1.5 years and 2.5 years, respectively. Between 0% and 150% of the performance stock units will vest on the third anniversary of its grant date.

In August 2021, the Company granted the Company's CEO 379,635 restricted stock units, which are subject to both time-based and performance-based vesting conditions. The performance stock units consist of three equal tranches (each, a "Performance Tranche"), based on achievement of a share price condition if the Company achieves share price targets of $60.00, $80.00, and $100.00 over 60 consecutive trading days during a performance period commencing on August 26, 2022 and ending on August 26, 2026. To the extent any of the performance-based requirements are met, the Company's CEO must also provide continued service to the Company through at least August 26, 2024 to receive any shares of common stock underlying the grant and through August 26, 2026 to receive all of the shares of common stock underlying the performance units that have satisfied the applicable performance-based requirement.

The fair value of each of the Performance Tranches was $3.0 million, $2.8 million, and $2.6 million, respectively, and have a grant date fair value per share of restricted stock of $23.94, $21.93, and $20.30, respectively, which was estimated using a Monte-Carlo lattice model. At September 30, 2021, the Company had unrecognized employee stock-based compensation expense of approximately $2.9 million, $2.7 million, and $2.5 million, which is expected to be recognized over the remaining 2.9 years, 3.9 years, and 4.9 years, respectively. Between 0% and 100% of the performance stock units will vest on each of the tranche dates.

During the three and nine months ended September 30, 2021, the Company recognized $0.4 million and $0.7 million, respectively, of stock-based compensation related to these performance stock units based on a performance measurement of 100%. The compensation expense will not be reversed if the performance metrics are not met.

Employee Stock Purchase Plan

In November 2013, the Company adopted the Company's 2014 Employee Stock Purchase Plan ("ESPP"). The ESPP is designed to enable eligible employees to periodically purchase shares of the Company's common stock at a discount through payroll deductions of up to 10% of their eligible compensation, subject to any plan limitations. At the end of each six-month offering period, employees are able to purchase shares at a price per share equal to 85% of the lower of the fair market value of the Company's common stock on the first trading day of the offering period or on the last trading day of the offering period. Offering periods generally commence and end in May and November of each year.

As of September 30, 2021, the Company has reserved 3,068,352 shares of its common stock for issuance under the ESPP. The ESPP has an evergreen provision pursuant to which the share reserve will automatically increase on January 1st of each year in an amount equal to 1% of the total number of shares of capital stock outstanding on December 31st of the preceding calendar year, although the Company’s board of directors may provide for a lesser increase, or no increase, in any year.

Stock-Based Compensation Expense

Total stock-based compensation expense recorded in the condensed consolidated statements of operations was as follows:


	Three Months Ended				Nine Months Ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
	(in thousands)				(in thousands)
Cost of revenue	$	278	$	122	$	530	$	412
Sales and marketing	4,583		2,309		10,426		5,928
Technology and development	3,828		2,061		8,195		5,469
General and administrative	3,087		2,504		8,299		7,935
Merger, acquisition, and restructuring costs	48		354		1,071		1,554
Total stock-based compensation expense	$	11,824	$	7,350	$	28,521	$	21,298

Income Taxes	9 Months Ended
Income Taxes	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes In determining quarterly provisions for income taxes, the Company uses the annual estimated effective tax rate applied to the actual year-to-date income. The Company's annual estimated effective tax rate differs from the statutory rate primarily as a result of state taxes, foreign taxes, deductible stock option expenses, nondeductible executive compensation, and changes in the Company's valuation allowance. The Company adopted ASU 2019-12, during the three months ended March 31, 2021. There was no material impact to the quarterly income tax provision. The Company recorded an income tax benefit of $4.7 million and expense of $0.4 million for the three months ended September 30, 2021 and 2020, respectively and an income tax benefit of $92.2 million and expense of $0.5 million for the nine months ended September 30, 2021 and 2020, respectively. The tax benefit for the three and nine months ended September 30, 2021 is primarily the result of the partial release of the domestic valuation allowance of $56.2 million related to the SpotX Acquisition, as well as the income tax benefit of a portion of the current year projected loss. The net deferred tax liabilities recorded in connection with the SpotX and SpringServe Acquisitions provided additional sources of taxable income to support the realizability of pre-existing deferred tax assets, and, as a result, the Company released a portion of its domestic valuation allowance and recognized a current benefit for a portion of the Company's projected losses. The Company continues to maintain a partial valuation allowance for the domestic deferred tax assets. On March 11, 2021, the U.S. President signed into law the American Rescue Plan Act of 2021 ("ARP Act")—a $1.9 trillion coronavirus disease 2019 ("COVID-19") relief package. The ARP Act had limited income tax provisions. The Company has determined that the ARP Act will not have a material impact on the Company for the year ended December 31, 2021. On March 27, 2020, the U.S. President signed into law the Coronavirus Aid, Relief, and Economic Security Act ("CARES Act"), in response to the COVID-19 pandemic. The CARES Act is meant to infuse negatively affected companies with various tax cash benefits to ease the impact of the COVID-19 pandemic. The CARES Act, among other things, includes provisions relating to refundable payroll tax credits, deferment of employer-side social security payments, and net operating loss carryback periods. The Company has determined the tax implications of the CARES Act will not be material. In addition, various foreign jurisdictions where the Company has activity have enacted or are considering enacting a variety of measures that could impact our tax liabilities. The Company is monitoring new legislation and evaluating the potential tax implications of these measures globally. Due to uncertainty as to the realization of benefits from the Company's domestic and certain international deferred tax assets, including net operating loss carryforwards and research and development tax credits, the Company has a partial valuation allowance reserved against such assets. The Company intends to continue to maintain a partial valuation allowance on the deferred tax assets until there is sufficient evidence to support the reversal of all or some additional portion of these allowances. Due to the net operating loss carryforwards, all of the Company's United States federal and a majority of its state returns are open to examination by the Internal Revenue Service and state jurisdictions for all years since inception. The 2017 U.S. Income Tax Return for Telaria, Inc. was under examination by the IRS, which was closed during the period ended June 30, 2021 with no change to tax as reported. For the Netherlands and the United Kingdom, all tax years remain open for examination by the local country tax authorities, for France only 2018 forward are open for examination, for Singapore 2017 and forward are open for examination, for Australia, Brazil, Canada, Germany, Italy, New Zealand, and Malaysia 2016 and forward are open for examination, and for Japan 2014 and forward remain open for examination. Pursuant to Section 382 of the Internal Revenue Code, the Company and Telaria, Inc. both underwent ownership changes for tax purposes (i.e. a more than 50% change in stock ownership in aggregated 5% shareholders) on April 1, 2020 due to the Telaria Merger. As a result, the use of our total domestic NOL carryforwards and tax credits generated prior to the ownership change will be subject to annual use limitations under Section 382 and Section 383 of the Code and comparable state income tax laws. The Company believes that the ownership change will not impact our ability to utilize substantially all of our NOLs and state research and development carryforward tax credits to the extent it will generate taxable income that can be offset by such losses. The Company reasonably expects its federal research and development carryforward tax credits will not be recovered prior to expiration. There was no material change to the Company's unrecognized tax benefits in the nine months ended September 30, 2021 and the Company does not expect to have any material changes to unrecognized tax benefits through the end of the fiscal year.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 21
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32857-109319

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-URI http://asc.fasb.org/extlink&oid=122134291&loc=d3e330215-122817

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 17
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32809-109319

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.5.Q1)
-URI http://asc.fasb.org/extlink&oid=122134291&loc=d3e330036-122817

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 14
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32705-109319

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 270
-Section 50
-Paragraph 1
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

Lease Obligations

9 Months Ended

Sep. 30, 2021

Leases [Abstract]

Lease Obligations

Lease ObligationsFor the three months ended September 30, 2021 and 2020, the Company recognized $4.9 million and $3.7 million, respectively, and $15.7 million and $9.7 million during the nine months ended September 30, 2021 and 2020, respectively, of lease expense under ASC 842, which included operating lease expenses associated with leases included in the lease liability and ROU asset on the condensed consolidated balance sheet. In addition, for the three months ended September 30, 2021 and 2020, the

Company recognized $0.4 million and $0.4 million, respectively, and $1.0 million and $0.8 million during the nine months ended September 30, 2021 and 2020, respectively, of lease expense related to short-term leases, and $9.9 million and $5.6 million during the three months ended September 30, 2021 and 2020, respectively, and $24.6 million and $14.0 million during the nine months ended September 30, 2021 and 2020, respectively, of variable and cloud-based services related to data centers that are not included in the ROU asset or lease liability balances. As part of restructuring activities associated with the SpotX Acquisition, during the nine months ended September 30, 2021, the Company recognized $2.5 million of lease related loss contracts, which is included in the lease expense under ASC 842.

The Company also received rental income of $1.0 million and $1.2 million for real estate leases for which it subleases the property to third parties during the three months ended September 30, 2021 and 2020, respectively and $3.3 million and $2.5 million for the nine months ended September 30, 2021 and 2020, respectively.

As of September 30, 2021, a weighted average discount rate of 5.05% has been applied to the remaining lease payments to calculate the lease liabilities included within the condensed consolidated balance sheet. The lease terms of the Company’s operating leases generally range from one year to ten years, and the weighted average remaining lease term of leases included in the lease liability is 6.34 years as of September 30, 2021.

The maturity of the Company's lease liabilities associated with leases included in the lease liability and ROU asset were as follows as of September 30, 2021 (in thousands):


Fiscal Year
Remaining 2021	$	4,093
2022	18,645
2023	15,193
2024	12,868
2025	7,286
Thereafter	25,921
Total lease payments (undiscounted)	84,006
Less: imputed interest	(12,974)
Lease liabilities—total (discounted)	$	71,032

Commitments and Contingencies	9 Months Ended
Commitments and Contingencies	Sep. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Commitments The Company has commitments under non-cancelable operating leases for facilities, certain equipment, and its managed data center facilities (Note 11). As of September 30, 2021 and December 31, 2020, the Company had $5.1 million and $6.3 million, respectively, of letters of credit associated with office leases available for borrowing, on which there were no outstanding borrowings as of either date. Guarantees and Indemnification The Company’s agreements with sellers, buyers, and other third parties typically obligate the Company to provide indemnity and defense for losses resulting from claims of intellectual property infringement, damages to property or persons, business losses, or other liabilities. Generally, these indemnity and defense obligations relate to the Company’s own business operations, obligations, and acts or omissions. However, under some circumstances, the Company agrees to indemnify and defend contract counterparties against losses resulting from their own business operations, obligations, and acts or omissions, or the business operations, obligations, and acts or omissions of third parties. For example, because the Company’s business interposes the Company between buyers and sellers in various ways, buyers often require the Company to indemnify them against acts and omissions of sellers, and sellers often require the Company to indemnify them against acts and omissions of buyers. In addition, the Company’s agreements with sellers, buyers, and other third parties typically include provisions limiting the Company’s liability to the counterparty, and the counterparty’s liability to the Company. These limits sometimes do not apply to certain liabilities, including indemnity obligations. These indemnity and limitation of liability provisions generally survive termination or expiration of the agreements in which they appear. The Company has also entered into indemnification agreements with its directors, executive officers, and certain other officers that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors, officers, or employees. No material demands have been made upon the Company to provide indemnification under such agreements and there are no claims that the Company is aware of that could have a material effect on the Company’s consolidated financial statements. Litigation The Company and its subsidiaries may from time to time be parties to legal or regulatory proceedings, lawsuits and other claims incident to their business activities and to the Company’s status as a public company. Such matters may include, among other things, assertions of contract breach or intellectual property infringement, claims for indemnity arising in the course of the Company’s business, regulatory investigations or enforcement proceedings, and claims by persons whose employment has been terminated. Such matters are subject to many uncertainties, and outcomes are not predictable with assurance. Consequently, management is unable to ascertain the ultimate aggregate amount of monetary liability, amounts which may be covered by insurance or recoverable from third parties, or the financial impact with respect to such matters as of September 30, 2021. However, based on management’s knowledge as of September 30, 2021, management believes that the final resolution of these matters known at such date, individually and in the aggregate, will not have a material adverse effect upon the Company’s consolidated financial position, results of operations or cash flows. Employment Contracts The Company has entered into severance agreements with certain employees and officers. The Company may be required to pay severance and accelerate the vesting of certain equity awards in the event of involuntary terminations.

SVB Loan Agreement	9 Months Ended
SVB Loan Agreement	Sep. 30, 2021
Debt Disclosure [Abstract]
SVB Loan Agreement	SVB Loan AgreementOn September 25, 2020, the Company amended and restated its loan and security agreement with Silicon Valley Bank ("SVB") (the "Loan Agreement"), which was scheduled to expire on September 26, 2020. The Loan Agreement provided a senior secured revolving credit facility of up to the lesser of $60.0 million and 85% of eligible accounts receivable, with a maturity date of September 25, 2022. The Loan Agreement included a letter of credit, foreign exchange and cash management facility with a sublimit up to $10.0 million. On April 30, 2021, the Company entered into the Credit Agreement, as defined in Note 15. In connection with entering into the Credit Agreement, the Loan Agreement with SVB was terminated on April 30, 2021. As of April 30, 2021, there were no amounts outstanding under the Loan Agreement.

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-URI http://asc.fasb.org/topic&trid=2208564

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
-Paragraph 1C
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495334-112611

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495371-112611

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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-Section 50
-Paragraph 1I
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495371-112611

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(c))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-Subparagraph (g)
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495334-112611

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495334-112611

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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-Paragraph 1E
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495348-112611

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

+ Details

Convertible Senior Notes and Capped Call Transactions

9 Months Ended

Sep. 30, 2021

Debt Disclosure [Abstract]

Convertible Senior Notes and Capped Call Transactions

In March 2021, the Company issued $400.0 million aggregate principal amount of 0.25% convertible senior notes in a private placement, including $50.0 million aggregate principal amount of such notes pursuant to the exercise in full of the over-allotment options of the initial purchasers (collectively, the ("Convertible Senior Notes")). The Convertible Senior Notes will mature on March 15, 2026, unless earlier repurchased, redeemed or converted. The total net proceeds from the offering, after deducting debt issuance costs, paid by the Company, were approximately $388.6 million. The Company used approximately $39.0 million of the net proceeds from the offering to pay for the Capped Call Transactions (as described below).

The Convertible Senior Notes are senior, unsecured obligations and (i) will be equal in right of payment with the existing and future senior, unsecured indebtedness; (ii) senior in right of payment to any of the Company’s future indebtedness that is expressly subordinated to the Convertible Senior Notes; (iii) effectively subordinated to the Company’s existing and future secured indebtedness, to the extent of the value of the collateral securing that indebtedness, including amounts outstanding under our Existing Loan Agreement or our New Credit Facilities (see Note 15); and (iv) structurally subordinated to all existing and future indebtedness and other liabilities, including trade payables, and (to the extent we are not a holder thereof) preferred equity, if any, of the Company’s subsidiaries that do not guarantee the Convertible Senior Notes.

The Convertible Senior Notes accrue interest at 0.25% per annum payable semi-annually in arrears on March 15 and September 15 of each year, beginning on September 15, 2021. The Convertible Senior Notes will mature on March 15, 2026 unless they are redeemed, repurchased or converted prior to such date. The Convertible Senior Notes are convertible at the option of holders only during certain periods and upon satisfaction of certain conditions.

Holders will have the right to convert their notes (or any portion of a note in an authorized denomination), in the following circumstances: (i) during any calendar quarter commencing after the calendar quarter ending on June 30, 2021, if the last reported sale price per share of the Company’s common stock exceeds 130% of the conversion price for each of at least 20 trading days during the 30 consecutive trading days ending on, and including, the last trading day of the immediately preceding calendar quarter; (ii) during the five consecutive business days immediately after any ten consecutive trading day period (such ten consecutive trading day period, the "measurement period") in which the trading price per $1,000 principal amount of notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price per share of the Company’s common stock on such trading day and the conversion rate on such trading day; (iii) upon the occurrence of certain corporate events or distributions on the Company’s common stock; (iv) if the Company calls such Convertible Senior Notes for redemption; and (v) on or after September 15, 2025, until the close of business on the second scheduled trading day immediately before the maturity date, holders of the Convertible Senior Notes may, at their option, convert all or a portion of their Convertible Senior Notes regardless of the foregoing conditions.at any time from, and including, September 15, 2025 until the close of business on the second scheduled trading day immediately before the maturity date.

Upon conversion, the Convertible Senior Notes may be settled in shares of the Company’s common stock, cash or a combination of cash and shares of the Company’s common stock, at the Company’s election. All conversions with a conversion date that occurs on or after September 15, 2025 will be settled using the same settlement method, and the Company will send notice of such settlement method to noteholders no later than the open of business on September 15, 2025.

The Company may not redeem the Convertible Senior Notes at their option at any time before March 20, 2024. Subject to the terms of the indenture, the Company has the right, at its election, to redeem all, or any portion (subject to the partial redemption limitation) in an authorized denomination, of the Convertible Senior Notes, at any time, and from time to time, on a redemption date on or after March 20, 2024 and on or before the 40th scheduled trading day immediately before the maturity date, for cash, but only if the "last reported sale price," as defined under the Offering Memorandum, per share of common stock exceeds 130% of the “conversion price” on (i) each of at least 20 trading days, during the 30 consecutive trading days ending on, and including, the trading day immediately before the date the Company sends the related redemption notice; and (ii) the trading day immediately before the date we send such notice. In addition, calling any note for redemption will constitute a "make-whole fundamental change" (as defined below) with respect to that note, in which case the conversion rate applicable to the conversion of that note will be increased in certain circumstances if it is converted after it is called for redemption. If the Company elects to redeem less than all of the outstanding notes, then the redemption will not constitute a make-whole fundamental change with respect to the notes not called for redemption, and holders of the notes not called for redemption will not be entitled to an increased conversion rate for such notes as described above on account of the redemption, except to the limited extent described further below. No sinking fund is provided for the Convertible Senior Notes, which means that the Company is not required to redeem or retire the Convertible Senior Notes periodically.

If a fundamental change occurs, then each noteholder will have the right to require the Company to repurchase its notes (or any portion thereof in an authorized denomination) for cash on a date (the "fundamental change repurchase date") of the Company’s choosing, which must be a business day that is no more than 45, nor less than 20, business days after the date Magnite distributes the related fundamental change notice.

If an event of default occurs with respect to the Company or any guarantor, then the principal amount of, and all accrued and unpaid interest on, all of the notes then outstanding will immediately become due and payable without any further action or notice by any person. If an event of default (other than an event of default described below with respect to Magnite or any guarantor and not solely with respect to a significant subsidiary of the Company’s or a guarantor, other than the Company or such guarantor) occurs and is continuing, then, except as described below under the caption —Special interest as sole remedy for certain reporting defaults, the trustee, by notice to the Company, or noteholders of at least 25% of the aggregate principal amount of notes then outstanding, by written notice to us and the trustee, may declare the principal amount of, and all accrued and unpaid interest on, all of the notes then outstanding to become due and payable immediately.

The Convertible Senior Notes have an initial conversion rate of 15.6539 shares of common stock per $1,000 principal amount of the Convertible Senior Notes, which will be subject to customary anti-dilution adjustments in certain circumstances.

In connection with the pricing of the Convertible Senior Notes, the Company entered into privately negotiated capped call transactions with various financial institutions (the "Capped Call Transactions"). The Capped Call Transactions were entered into with third party broker-dealers to limit the potential dilution that would occur if the Company has to settle the conversion value in excess of the principal in shares. This exposure will be covered (i.e., the Company will receive as many shares as are required to be issued between the conversion price of $63.8818 and the maximum price of $91.2600). Any shares required to be issued by the Company over this amount would have net earnings per share dilution impact. By entering into the Capped Call Transactions, the Company expects to reduce the potential dilution to its common stock (or, in the event the conversion is settled in cash, to reduce its cash payment obligation) in the event that at the time of conversion its stock price exceeds the conversion price under the Convertible Senior Notes. The Company paid $39.0 million for the Capped Call Transactions, which was recorded as additional paid-in capital, using a portion of the gross proceeds from the sale of the Convertible Senior Notes. The cost of the Capped Call Transactions is not expected to be tax deductible as the Company did not elect to integrate the capped call into the Convertible Senior Notes for tax purposes. The cost of the Capped Call Transaction was recorded as a reduction of the Company’s additional paid-in capital in the accompanying condensed consolidated financial statements.

As noted in Note 1, the Company early adopted ASU 2020-06 effective January 1, 2021. The Company has not elected the fair value option, the embedded conversion features are not required to be bifurcated under the accounting guidance, and the convertible debt was not issued with a substantial premium. As such, the Company accounted for the Convertible Senior Notes as a liability in its entirety. Under the guidance, all the embedded features of the Convertible Senior Notes met the definition of a derivative. These features included a contingent call option, contingent put options, and conversion features. The contingent call option and contingent put options are clearly and closely related to the debt host and, therefore, do not require bifurcation. As the conversion features are indexed to the Company’s own equity and would be equity classified if they were freestanding instruments, the scope exception in ASC 815-10-15-74(a) applies and these conversion features will not be bifurcated under ASC 815.

The new accounting guidance also eliminated the bifurcation models of ASC 470-20 and eliminated the treasury method approach to earnings per share. Accordingly, earnings per share on convertible debt instruments should only be calculated under the If-Converted method. Under the guidance above, the Company will assume settlement in shares.

The following table summarizes the Convertible Senior Notes at September 30, 2021:


	September 30, 2021
	(in thousands)
Convertible Senior Notes	$	400,000
Unamortized debt issuance costs	(10,215)
Debt, non-current, net of debt issuance costs	$	389,785

The Company incurred debt issuance costs of $11.4 million in March 2021. The Convertible Senior Notes are presented net of issuance costs on the Company's condensed consolidated balance sheet. The debt issuance costs are amortized on an effective interest basis over the term of the Convertible Senior Notes and are included in interest expense and amortization of debt discount in the accompanying condensed consolidated statements of operations. The following table sets forth interest expense related to the Convertible Senior Notes for the three and nine months ended September 30, 2021:


	September 30, 2021
	Three Months Ended		Nine Months Ended
	(in thousands)
Contractual interest expense	$	250	$	536
Amortization of debt issuance costs	572		1,227
Total interest expense	$	822	$	1,763
Effective interest rate			0.82		%

Amortization expense for the Company's debt issuance costs for the remainder of 2021 and for fiscal years 2022 through 2026 is as follows:


Fiscal Year	Debt Issuance Costs
Remaining 2021	$	572
2022	2,288
2023	2,288
2024	2,288
2025	2,288
2026	491
Total	$	10,215

Credit Facility

On April 30, 2021, the Company entered into a credit agreement (the "Credit Agreement") with Goldman Sachs Bank USA as administrative agent and collateral agent, and other lender parties thereto. The Credit Agreement provides for a $360.0 million seven-year senior secured term loan facility ("Term Loan B Facility") and a $52.5 million senior secured revolving credit facility (the "Revolving Credit Facility"). As part of the Term Loan B Facility, the Company received $325 million in proceeds, net of discounts and fees, which were used to finance the SpotX Acquisition and related transactions, and for general corporate purposes. Loans, if any, under the Revolving Credit Facility are expected to be used for general corporate purposes. The obligations under the Credit Agreement are secured by substantially all of the assets of the Company and those of its subsidiaries that are guarantors under the Credit Agreement.

Amounts outstanding under the Credit Agreement accrue interest at a rate equal to either, (1) for the Term Loan B Facility, at the Company’s election, the Eurodollar Rate (as defined in the Credit Agreement) plus a margin of 5.00% per annum, or ABR (as defined in the Credit Agreement) plus a margin of 4.00%, and (2) for the Revolving Credit Facility, at the Company’s election, the Eurodollar Rate plus a margin of 4.25% to 4.75%, or ABR plus a margin of 3.25% to 3.75%, in each case, depending on the Company’s first lien net leverage ratio.

The covenants of the Credit Agreement include customary negative covenants that, among other things, restrict the Company’s ability to incur additional indebtedness, grant liens and make certain acquisitions, investments, asset dispositions and restricted payments. In addition, the Credit Agreement contains a financial covenant, tested on the last day of any fiscal quarter if

utilization of the Revolving Credit Facility exceeds 35% of the total revolving commitments, that requires the Company to maintain a first lien net leverage ratio not greater than 3.25 to 1.00.

The Credit Agreement includes customary events of default, and customary rights and remedies upon the occurrence of any event of default thereunder, including rights to accelerate the loans, terminate the commitments thereunder and realize upon the collateral securing the obligations under the Credit Agreement. The Credit Agreement calls for customary scheduled loan amortization payments of 0.25% of the initial principal balance payable quarterly (i.e. 1% in aggregate per year) as well as a provision that requires the Company to prepay the Term Loan B based on a calculation of cumulative free cash flow generated by the company as defined within the terms of the Agreement.

On June 28, 2021, the Company entered into an Incremental Assumption Agreement (the "Incremental Agreement") to the Credit Agreement. Pursuant to the terms of the Incremental Agreement, the Company’s existing revolving credit facility under the Credit Agreement was increased by $12.5 million (the "Incremental Revolver"), and the letter of credit sublimit under the Credit Agreement was increased by $5.0 million. The Incremental Revolver bears the same interest rate as the existing revolving credit facility and has the same maturity date as the existing revolving credit facility. No other terms of the Credit Agreement were amended. As a result, amounts available under the Revolving Credit Facility were $65.0 million. At September 30, 2021, amounts available under the Revolving Credit Facility were $59.9 million, net of letters of credit outstanding in the amount of $5.1 million.

The following table summarizes the Term Loan B Facility at September 30, 2021:



	(in thousands)
Term Loan B Facility	$	359,100
Unamortized debt discounts	(10,136)
Unamortized debt issuance costs	(15,816)
Debt, net of debt issuance costs	$	333,148

The Company incurred debt issuance costs of $27.7 million in April 2021, of which $10.8 million were associated with debt discount netted against the proceeds and $16.9 million were associated with other deferred financing costs associated with the Term Loan B Facility. Debt outstanding under the Term Loan B Facility are presented net of issuance costs on the Company's condensed consolidated balance sheet. The debt issuance costs are amortized on an effective interest basis over the term of the Term Loan B Facility and are included in interest expense and amortization of debt discount in the accompanying condensed consolidated statements of operations. The following table sets forth interest expense related to the Term Loan B Facility for the three and nine months ended September 30, 2021:


	September 30, 2021
	Three Months Ended		Nine Months Ended
	(in thousands)
Contractual interest expense	$	5,290	$	8,798
Amortization of debt discount	399		664
Amortization of debt issuance costs	622		1,036
Total interest expense	$	6,311	$	10,498
Effective interest rate			7.00		%

Amortization expense for the Term Loan B Facility debt discount and debt issuance costs for the remainder of 2021 and for fiscal years 2022 through 2028 is as follows:


Fiscal Year	Debt Discount		Debt Issuance Costs
Remaining 2021	$	398	$	620
2022	1,580		2,466
2023	1,564		2,441
2024	1,548		2,416
2025	1,532		2,391
Thereafter	3,514		5,482
Total	$	10,136	$	15,816

Credit Facility

9 Months Ended

Sep. 30, 2021

Debt Disclosure [Abstract]

Credit Facility

Convertible Senior Notes and Capped Call Transactions

The following table summarizes the Convertible Senior Notes at September 30, 2021:


	September 30, 2021
	(in thousands)
Convertible Senior Notes	$	400,000
Unamortized debt issuance costs	(10,215)
Debt, non-current, net of debt issuance costs	$	389,785


	September 30, 2021
	Three Months Ended		Nine Months Ended
	(in thousands)
Contractual interest expense	$	250	$	536
Amortization of debt issuance costs	572		1,227
Total interest expense	$	822	$	1,763
Effective interest rate			0.82		%

Amortization expense for the Company's debt issuance costs for the remainder of 2021 and for fiscal years 2022 through 2026 is as follows:


Fiscal Year	Debt Issuance Costs
Remaining 2021	$	572
2022	2,288
2023	2,288
2024	2,288
2025	2,288
2026	491
Total	$	10,215

Credit Facility

utilization of the Revolving Credit Facility exceeds 35% of the total revolving commitments, that requires the Company to maintain a first lien net leverage ratio not greater than 3.25 to 1.00.

The following table summarizes the Term Loan B Facility at September 30, 2021:



	(in thousands)
Term Loan B Facility	$	359,100
Unamortized debt discounts	(10,136)
Unamortized debt issuance costs	(15,816)
Debt, net of debt issuance costs	$	333,148


	September 30, 2021
	Three Months Ended		Nine Months Ended
	(in thousands)
Contractual interest expense	$	5,290	$	8,798
Amortization of debt discount	399		664
Amortization of debt issuance costs	622		1,036
Total interest expense	$	6,311	$	10,498
Effective interest rate			7.00		%

Amortization expense for the Term Loan B Facility debt discount and debt issuance costs for the remainder of 2021 and for fiscal years 2022 through 2028 is as follows:


Fiscal Year	Debt Discount		Debt Issuance Costs
Remaining 2021	$	398	$	620
2022	1,580		2,466
2023	1,564		2,441
2024	1,548		2,416
2025	1,532		2,391
Thereafter	3,514		5,482
Total	$	10,136	$	15,816

Subsequent Events	9 Months Ended
Subsequent Events	Sep. 30, 2021
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Subsequent to September 30, 2021, the Company entered into a data center contract renewal, with future commitments of approximately $2.2 million per year over 3.0 years, beginning on December 1, 2021. On October 20, 2021, the Company granted 91,582 restricted stock units to the Company's employees. Of the RSUs granted, 25,557 will vest over four years from issuance with 25% after one year, and the remainder vesting quarterly thereafter, and 66,025 will vest 50% on October 1, 2022 and 50% October 1, 2023.

Organization and Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation and Summary of Significant Accounting Policies	Basis of Presentation and Summary of Significant Accounting Policies The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with United States Generally Accepted Accounting Principles, or GAAP, for interim financial information and the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring adjustments) considered necessary for a fair statement of the results for the interim period presented have been included. Operating results for the three and nine months ended September 30, 2021 are not necessarily indicative of the results that may be expected for any future interim period, the year ending December 31, 2021, or for any future year. The condensed consolidated balance sheet at December 31, 2020 has been derived from the audited financial statements at that date, but does not include all of the disclosures required by GAAP. The accompanying condensed consolidated financial statements should be read in conjunction with the Company's audited consolidated financial statements and notes thereto for the year ended December 31, 2020 included in its 2020 Annual Report on Form 10-K. Aside from the adoption of ASU 2020-06, as described below, there have been no significant changes in the Company's accounting policies from those disclosed in its audited consolidated financial statements and notes thereto for the year ended December 31, 2020 included in its Annual Report on Form 10-K.
Use of Estimates	Use of Estimates The preparation of condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported and disclosed financial statements and accompanying footnotes. Due to the economic uncertainty as a result of the COVID-19 pandemic, it has become more difficult to apply certain assumptions and judgments into these estimates. The extent of the impact of COVID-19 pandemic on the Company's operational and financial performance will depend on future developments, which are highly uncertain and cannot be predicted, including but not limited to, the duration and spread of the pandemic, its severity, including any resurgence, the actions to contain the virus or treat its impact, and how quickly and to what extent normal economic and operating conditions can resume. During the nine months ended September 30, 2021, this uncertainty continued to result in a higher level of judgment related to its estimates and assumptions. As of the date of issuance of the condensed consolidated financial statements for the three and nine months ended September 30, 2021, the Company is not aware of any specific event or circumstance that would require the Company to update its estimates, judgments, or revise the carrying value of its assets or liabilities. These estimates may change, as new events occur and additional information is obtained, and are recognized in the consolidated financial statements as soon as they become known. Actual results could differ materially from these estimates.
Recently Adopted and Recent Accounting Pronouncements	Recently Adopted Accounting Standards On January 1, 2021, the Company adopted ASU 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity's Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity (ASU "2020-06") on a prospective basis, which simplifies the accounting for convertible instruments by reducing the number of accounting models available for convertible debt instruments that require separating embedded conversion features from convertible instruments. This guidance also eliminates the treasury stock method to calculate diluted earnings per share for convertible instruments and requires the use of the if-converted method. The adoption of this standard is included in the financial statements as of September 30, 2021 and for the three and nine months ended September 30, 2021 and September 30, 2020, respectively. Refer to Note 14—"Convertible Senior Notes" for additional information related to accounting for convertible debt issued during the nine months ended September 30, 2021. On January 1, 2021, the Company adopted ASU 2019-12—Simplifying the Accounting for Income Taxes ("ASU 2019-12"). ASU 2019-12 simplifies the accounting for income taxes by removing certain exceptions to general principles in Topic 740 and clarifies and amends existing guidance for clarity and consistent application. There was no material impact to the quarterly or year to date income tax provision. Recent Accounting Pronouncements In March 2020, the FASB issued Update No. 2020-04, Reference Rate Reform (Topic 848), which provides temporary optional guidance to companies impacted by the transition away from the LIBOR. The amendment provides certain expedients and exceptions to applying GAAP in order to lessen the potential accounting burden when contracts, hedging relationships, and other transactions that reference LIBOR as a benchmark rate are modified. Further, in January 2021, the FASB issued Update No. 2021-01, Reference Rate Reform (Topic 848), which clarifies the scope of Topic 848 so that derivatives affected by the discounting transition are explicitly eligible for certain optional expedients and exceptions in Topic 848. These amendments are effective upon issuance and expire on December 31, 2022. The Company is currently assessing the impact of the LIBOR transition on the Company's condensed consolidated financial statements. In July 2021, the FASB issued Update No. 2021-05, Leases (Topic 842)—Lessors – Certain Leases with Variable Lease Payments ("ASU 2021-05"). ASU 2021-05 requires a lessor to classify a lease with variable lease payments that do not depend on an index or rate as an operating lease if specified criteria are met. This guidance will be effective on January 1, 2022, either retrospectively to leases that commenced or were modified on or after our adoption of ASU 2016-02 on January 1, 2019, or on a prospective basis, with early adoption permitted. The Company is currently assessing the impact of the new guidance on the Company's condensed consolidated financial statements. The Company does not believe there are any other recently issued and effective or not yet effective pronouncements that would have or are expected to have any significant effect on the Company’s financial position, cash flows or results of operations.

Net Loss Per Share (Tables)

9 Months Ended

Sep. 30, 2021

Earnings Per Share [Abstract]

Schedule of Net Loss Per Share, Basic and Diluted

The following table presents the basic and diluted net loss per share:


	Three Months Ended				Nine Months Ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
	(in thousands, except per share data)
Basic and Diluted Income (Loss) Per Share:
Net loss	$	(24,319)	$	(10,515)	$	(388)	$	(59,318)
Weighted-average common shares outstanding	131,501		110,416		124,325		91,371


Weighted-average common shares outstanding used to compute net loss per share	131,501		110,416		124,325		91,371
Basic and diluted net loss per share	$	(0.18)	$	(0.10)	$	—	$	(0.65)

Schedule of Antidilutive Securities Excluded from Computation of Diluted Net Loss Per Share


	Three Months Ended		Nine Months Ended
	September 30, 2021	September 30, 2020	September 30, 2021	September 30, 2020
	(in thousands)		(in thousands)
Options to purchase common stock	4,116	1,920	4,712	1,720

Unvested restricted stock units	4,253	3,768	5,876	3,851
Unvested performance stock units	195	14	196	6
ESPP	11	30	49	40
Convertible Senior Notes	6,262	—	4,499	—
Total shares excluded from net loss per share	14,837	5,732	15,332	5,617

Revenue (Tables)

9 Months Ended

Sep. 30, 2021

Revenue from Contract with Customer [Abstract]

Schedule of Revenue Recognized on a Net Basis and on a Gross Basis

The following table presents our revenue recognized on a net basis and on a gross basis for the three and nine months ended September 30, 2021 and September 30, 2020, respectively.


	Three Months Ended								Nine Months Ended
	September 30, 2021				September 30, 2020				September 30, 2021				September 30, 2020
	(in thousands, except percentages)
Revenue:
Net basis	$	105,866	80	%	$	59,913	98	%	$	258,236	84	%	$	138,063	99	%
Gross basis	26,005		20		1,069		2		48,891		16		1,562		1
Total	$	131,871	100	%	$	60,982	100	%	$	307,127	100	%	$	139,625	100	%

Summary of Disaggregation of Revenue

The following table presents our revenue by channel for the three and nine months ended September 30, 2021 and 2020:


	Three Months Ended								Nine Months Ended
	September 30, 2021				September 30, 2020				September 30, 2021				September 30, 2020
	(in thousands, except percentages)
Channel:
CTV	$	57,885	44	%	$	11,059	18	%	$	115,040	38	%	$	18,978	14	%
Desktop	30,573		23		20,901		34		80,166		26		51,468		37
Mobile	43,413		33		29,022		48		111,921		36		69,179		49
Total	$	131,871	100	%	$	60,982	100	%	$	307,127	100	%	$	139,625	100	%

The following table presents the Company's revenue disaggregated by geographic location, based on the location of the Company's sellers:


	Three Months Ended				Nine Months Ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
	(in thousands)				(in thousands)
United States	$	104,633	$	45,048	$	237,844	$	101,168

International	27,238		15,934		69,283		38,457
Total	$	131,871	$	60,982	$	307,127	$	139,625

Accounts Receivable, Allowance for Credit Loss

The following is a summary of activity in the allowance for doubtful accounts for the three and nine months ended September 30, 2021 and 2020:


	Three Months Ended				Nine Months Ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
	(in thousands)				(in thousands)
Allowance for doubtful accounts, Beginning Balance	$	3,279	$	4,672	$	2,360	$	3,400
Allowance for doubtful accounts, merger and acquisition-assumed	425		—		835		1,033
Write-offs	(14)		(1)		(35)		(1,897)
Increase (decrease) in provision for expected credit losses	342		(274)		852		1,854
Recoveries of previous write-offs	—		83		20		90
Allowance for doubtful accounts, September 30	$	4,032	$	4,480	$	4,032	$	4,480

Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2021

Fair Value Disclosures [Abstract]

Fair Value, Assets Measured on Recurring Basis

The table below sets forth a summary of financial instruments that are measured at fair value on a recurring basis at September 30, 2021:


	Total		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(in thousands)
Cash equivalents	$	7,869	$	7,869	$	—	$	—

The table below sets forth a summary of financial instruments that are measured at fair value on a recurring basis at December 31, 2020:


	Total		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(in thousands)
Cash equivalents	$	7,868	$	7,868	$	—	$	—

Other Balance Sheet Amounts (Tables)

9 Months Ended

Sep. 30, 2021

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of Accounts Payable and Accrued Expenses

Accounts payable and accrued expenses included the following:


	September 30, 2021		December 31, 2020
	(in thousands)
Accounts payable—seller	$	791,227	$	492,605
Accounts payable—trade	15,321		4,268
Accrued employee-related payables	20,544		12,442
Accrued holdback - indemnification claims	1,409		—
Total	$	828,501	$	509,315

Goodwill, Intangible Assets, and Capitalized Costs Incurred in Cloud Computing Arrangements (Tables)

9 Months Ended

Sep. 30, 2021

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Finite-Lived Intangible Assets

The Company’s intangible assets as of September 30, 2021 and December 31, 2020 included the following:


	September 30, 2021		December 31, 2020
	(in thousands)
Amortizable intangible assets:
Developed technology	$	373,558	$	77,658
Customer relationships	173,950		37,950
In-process research and development	14,630		8,030
Backlog	11,100		—
Non-compete agreements	2,070		70
Trademarks	1,400		—
Total identifiable intangible assets, gross	576,708		123,708
Accumulated amortization—intangible assets:
Developed technology	(57,282)		(21,905)
Customer relationships	(47,359)		(11,877)
In-process research and development	(449)		—
Backlog	(6,938)		—
Non-compete agreements	(756)		(42)
Trademarks	(353)		—
Total accumulated amortization—intangible assets	(113,137)		(33,824)
Total identifiable intangible assets, net	$	463,571	$	89,884

Schedule of Finite-Lived Intangible Assets, Future Amortization Expense

The estimated remaining amortization expense associated with the Company's intangible assets was as follows as of September 30, 2021:


Fiscal Year	Amount
	(in thousands)
Remaining 2021	$	42,527
2022	147,361
2023	101,996
2024	84,218
2025	66,668
Thereafter	20,801
Total	$	463,571

Business Combinations (Tables)

9 Months Ended

Sep. 30, 2021

Business Combination and Asset Acquisition [Abstract]

Unaudited Pro Forma Information


	Nine Months Ended
		September 30, 2020
	(in thousands)
Pro Forma Revenue		$	154,663
Pro Forma Net Loss		$	(69,706)


	Three Months Ended			Nine Months Ended
		September 30, 2020		September 30, 2021		September 30, 2020
		(in thousands)
Pro Forma Revenue		$	104,249	$	379,180	$	243,781
Pro Forma Net Income (Loss)		$	(29,651)	$	(88,187)	$	(157,803)

Purchase Consideration

The following table summarizes the total purchase consideration (in thousands):


Cash Consideration	$	640,000
Stock Consideration (Fair Value of Shares of Magnite common stock)	495,591
Working capital adjustment	65,152
Total purchase consideration	$	1,200,743

The following table summarizes the total estimated purchase consideration (in thousands):


Cash Consideration	$	31,136
SpotX initial cash investment in SpringServe	2,075
Fair value appreciation of SpotX purchase right	7,450
Indemnification claims - holdback	1,409
Total purchase consideration	$	42,070

Schedule of Recognized Identified Assets Acquired and Liabilities Assumed


Cash	$	81,967
Restricted cash	199
Accounts receivable	199,649
Prepaid and other assets, current	12,308
Fixed assets	5,093
Intangible assets	429,600
Right-of-use lease asset	11,785
Goodwill	790,466

Total assets to be acquired	1,531,067
Accounts payable and accrued expenses	205,913

Other current liabilities	7,169
Lease liabilities	12,625
Deferred tax liability, net	104,617
Total liabilities to be assumed	330,324
Total purchase price	$	1,200,743


Cash	$	1,062
Accounts receivable	3,234
Prepaid and other assets, current	157
Fixed assets	25
Intangible assets	23,400
Right-of-use lease asset	1,879
Goodwill	24,156

Total assets to be acquired	53,913
Accounts payable and accrued expenses	2,475
Other current liabilities	35
Lease liabilities	3,179
Deferred tax liability, net	6,154
Total liabilities to be assumed	11,843
Total preliminary purchase price	$	42,070

Schedule of Intangible Assets Acquired and Estimated Useful Life as of the Acquisition Date

The following table summarizes the components of the intangible assets and estimated useful lives as of the date of the SpotX Acquisition (dollars in thousands):


			Estimated Useful Life
Technology	$	280,400	5 years
Customer relationships	130,300		2 to 4 years
Backlog	11,100		<1 year
In-process research and development	5,800		3 years*
Non-compete agreements	1,500		1 year
Trademarks	500		<1 year
Total intangible assets acquired	$	429,600
* In-process research and development consists of six projects with a weighted-average useful life of 3.0 years. Amortization begins once associated projects are completed and it is determined the projects have alternative future use.

The following table summarizes the components of the intangible assets and estimated useful lives as of the date of the SpringServe Acquisition (dollars in thousands):


			Estimated Useful Life
Technology	$	15,500	5 years
Customer relationships	5,700		2 years
Trademarks and Trade Names	900		3 years
In-process research and development	800		3 years*
Non-compete agreements	500		2 years
Total intangible assets acquired	$	23,400
* In-process research and development consists of two projects with a weighted-average useful life of 3 years. Amortization begins once associated projects are completed and it is determined the projects have alternative future use.

Merger, Acquisition, and Restructuring Costs (Tables)

9 Months Ended

Sep. 30, 2021

Restructuring and Related Activities [Abstract]

Merger and Restructuring Costs

The following table summarizes merger, acquisition, and restructuring cost activity (in thousands):


	Three Months Ended				Nine Months Ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
	(in thousands)
Professional services (investment banking advisory, legal and other professional services)	$	1,064	$	952	$	28,032	$	9,533
Personnel related (severance and one-time termination benefit costs)	1,312		948		6,176		5,590
Non-cash stock-based compensation (double-trigger acceleration and severance)	48		354		1,070		1,554
Loss contracts (lease related)	—		—		2,500		—
Total merger, acquisition, and restructuring costs	$	2,424	$	2,254	$	37,778	$	16,677


	(in thousands)
Accrued merger, acquisition, and restructuring costs at December 31, 2020	$	2,935
Restructuring costs, personnel related and non-cash stock-based compensation	7,246
Restructuring activity, merger and acquisition loss contracts	2,500
Cash paid for restructuring costs	(5,035)
Non-cash loss contracts (lease related)	(2,500)
Non-cash stock-based compensation	(1,070)
Accrued merger, acquisition, and restructuring costs at September 30, 2021	$	4,076

Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2021

Share-based Payment Arrangement [Abstract]

Schedule of Share-based Compensation, Stock Options, Activity

A summary of stock option activity for the nine months ended September 30, 2021 is as follows:


	Shares Under Option	Weighted- Average Exercise Price		Weighted- Average Contractual Life	Aggregate Intrinsic Value
	(in thousands)				(in thousands)
Outstanding at December 31, 2020	6,695	$	5.61
Granted	302	$	38.99
Exercised	(1,393)	$	6.28

Forfeited	(306)	$	8.87
Outstanding at September 30, 2021	5,298	$	7.15	5.79 years	$	113,430
Exercisable at September 30, 2021	3,768	$	5.51	4.82 years	$	84,758

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions

The weighted-average input assumptions used by the Company were as follows:


	Three Months Ended				Nine Months Ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
Expected term (in years)	5.0		6.3		5.0		6.3
Risk-free interest rate	0.90	%	0.33	%	0.88	%	0.45	%
Expected volatility	79	%	68	%	79	%	67	%
Dividend yield	—	%	—	%	—	%	—	%

Schedule of Nonvested Restricted Stock Units Activity

A summary of restricted stock unit activity for the nine months ended September 30, 2021 is as follows:


	Number of Shares		Weighted-Average Grant Date Fair Value
	(in thousands)
Restricted stock units outstanding at December 31, 2020	9,286		$	5.30
Granted	2,816		$	38.54
Canceled	(779)		$	12.17
Vested and released	(3,873)		$	5.21
Restricted stock units outstanding at September 30, 2021	7,450		$	17.19
Restricted stock units outstanding and unvested*	7,413	*	$	17.24
*At September 30, 2021, outstanding restricted stock units included 37,318 units that were vested but deferred.

Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs for all Plans

Total stock-based compensation expense recorded in the condensed consolidated statements of operations was as follows:


	Three Months Ended				Nine Months Ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
	(in thousands)				(in thousands)
Cost of revenue	$	278	$	122	$	530	$	412
Sales and marketing	4,583		2,309		10,426		5,928
Technology and development	3,828		2,061		8,195		5,469
General and administrative	3,087		2,504		8,299		7,935
Merger, acquisition, and restructuring costs	48		354		1,071		1,554
Total stock-based compensation expense	$	11,824	$	7,350	$	28,521	$	21,298

Lease Obligations (Tables)

9 Months Ended

Sep. 30, 2021

Leases [Abstract]

Schedule of Maturity of Lease Liabilities

The maturity of the Company's lease liabilities associated with leases included in the lease liability and ROU asset were as follows as of September 30, 2021 (in thousands):


Fiscal Year
Remaining 2021	$	4,093
2022	18,645
2023	15,193
2024	12,868
2025	7,286
Thereafter	25,921
Total lease payments (undiscounted)	84,006
Less: imputed interest	(12,974)
Lease liabilities—total (discounted)	$	71,032

Convertible Senior Notes and Capped Call Transactions (Tables)

9 Months Ended

Sep. 30, 2021

Debt Disclosure [Abstract]

Schedule of Debt

The following table summarizes the Convertible Senior Notes at September 30, 2021:


	September 30, 2021
	(in thousands)
Convertible Senior Notes	$	400,000
Unamortized debt issuance costs	(10,215)
Debt, non-current, net of debt issuance costs	$	389,785

The following table summarizes the Term Loan B Facility at September 30, 2021:



	(in thousands)
Term Loan B Facility	$	359,100
Unamortized debt discounts	(10,136)
Unamortized debt issuance costs	(15,816)
Debt, net of debt issuance costs	$	333,148

Interest Income and Interest Expense Disclosure

The following table sets forth interest expense related to the Convertible Senior Notes for the three and nine months ended September 30, 2021:


	September 30, 2021
	Three Months Ended		Nine Months Ended
	(in thousands)
Contractual interest expense	$	250	$	536
Amortization of debt issuance costs	572		1,227
Total interest expense	$	822	$	1,763
Effective interest rate			0.82		%

The following table sets forth interest expense related to the Term Loan B Facility for the three and nine months ended September 30, 2021:


	September 30, 2021
	Three Months Ended		Nine Months Ended
	(in thousands)
Contractual interest expense	$	5,290	$	8,798
Amortization of debt discount	399		664
Amortization of debt issuance costs	622		1,036
Total interest expense	$	6,311	$	10,498
Effective interest rate			7.00		%

Schedule of Maturities of Long-term Debt

Amortization expense for the Company's debt issuance costs for the remainder of 2021 and for fiscal years 2022 through 2026 is as follows:


Fiscal Year	Debt Issuance Costs
Remaining 2021	$	572
2022	2,288
2023	2,288
2024	2,288
2025	2,288
2026	491
Total	$	10,215

Amortization expense for the Term Loan B Facility debt discount and debt issuance costs for the remainder of 2021 and for fiscal years 2022 through 2028 is as follows:


Fiscal Year	Debt Discount		Debt Issuance Costs
Remaining 2021	$	398	$	620
2022	1,580		2,466
2023	1,564		2,441
2024	1,548		2,416
2025	1,532		2,391
Thereafter	3,514		5,482
Total	$	10,136	$	15,816

Credit Facility - (Tables)

9 Months Ended

Sep. 30, 2021

Debt Disclosure [Abstract]

Schedule of Debt

The following table summarizes the Convertible Senior Notes at September 30, 2021:


	September 30, 2021
	(in thousands)
Convertible Senior Notes	$	400,000
Unamortized debt issuance costs	(10,215)
Debt, non-current, net of debt issuance costs	$	389,785

The following table summarizes the Term Loan B Facility at September 30, 2021:



	(in thousands)
Term Loan B Facility	$	359,100
Unamortized debt discounts	(10,136)
Unamortized debt issuance costs	(15,816)
Debt, net of debt issuance costs	$	333,148

Interest Income and Interest Expense Disclosure

The following table sets forth interest expense related to the Convertible Senior Notes for the three and nine months ended September 30, 2021:


	September 30, 2021
	Three Months Ended		Nine Months Ended
	(in thousands)
Contractual interest expense	$	250	$	536
Amortization of debt issuance costs	572		1,227
Total interest expense	$	822	$	1,763
Effective interest rate			0.82		%

The following table sets forth interest expense related to the Term Loan B Facility for the three and nine months ended September 30, 2021:


	September 30, 2021
	Three Months Ended		Nine Months Ended
	(in thousands)
Contractual interest expense	$	5,290	$	8,798
Amortization of debt discount	399		664
Amortization of debt issuance costs	622		1,036
Total interest expense	$	6,311	$	10,498
Effective interest rate			7.00		%

Schedule of Maturities of Long-term Debt

Amortization expense for the Company's debt issuance costs for the remainder of 2021 and for fiscal years 2022 through 2026 is as follows:


Fiscal Year	Debt Issuance Costs
Remaining 2021	$	572
2022	2,288
2023	2,288
2024	2,288
2025	2,288
2026	491
Total	$	10,215

Amortization expense for the Term Loan B Facility debt discount and debt issuance costs for the remainder of 2021 and for fiscal years 2022 through 2028 is as follows:


Fiscal Year	Debt Discount		Debt Issuance Costs
Remaining 2021	$	398	$	620
2022	1,580		2,466
2023	1,564		2,441
2024	1,548		2,416
2025	1,532		2,391
Thereafter	3,514		5,482
Total	$	10,136	$	15,816

Net Loss Per Share - Basic and Diluted Income (Loss) Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Basic and Diluted Income (Loss) Per Share:
Net loss	$ (24,319)	$ 36,808	$ (12,877)	$ (10,515)	$ (39,128)	$ (9,675)	$ (388)	$ (59,318)
Weighted-average common shares outstanding (in shares)	131,501			110,416			124,325	91,371
Basic net income (loss) per share (in shares)	$ (0.18)			$ (0.10)			$ 0	$ (0.65)
Diluted net income (loss) per share (in shares)	$ (0.18)			$ (0.10)			$ 0	$ (0.65)

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 40
-Section 65
-Paragraph 1
-Subparagraph (e)(4)
-URI http://asc.fasb.org/extlink&oid=123482062&loc=SL123482106-238011

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22583-107794

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

+ Details

Net Loss Per Share - Shares Excluded From Calculation of Diluted Net Loss Per Share (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from net loss per share (in shares)	14,837	5,732	15,332	5,617
Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from net loss per share (in shares)	4,116	1,920	4,712	1,720
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from net loss per share (in shares)	4,253	3,768	5,876	3,851
Performance stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from net loss per share (in shares)	195	14	196	6
ESPP
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from net loss per share (in shares)	11	30	49	40
Convertible Senior Notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from net loss per share (in shares)	6,262	0	4,499	0

Net Loss Per Share - Narrative (Details)	1 Months Ended	3 Months Ended	9 Months Ended
Net Loss Per Share - Narrative (Details)	Mar. 31, 2021	Sep. 30, 2021	Sep. 30, 2021 share
Convertible Senior Notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of shares issuable assuming conversion			6,261,560
Convertible Senior Notes \| Convertible Debt
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Conversion ratio	0.0156539
Performance stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Performance measurement percentage		100.00%	100.00%
Performance Shares, Granted April 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Performance measurement percentage		150.00%	150.00%
Performance shares, Granted April 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Performance measurement percentage		0.00%	0.00%
Performance shares, Granted August 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Performance measurement percentage		0.00%	0.00%

Revenue - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
Revenue - Narrative (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Percent of revenue (less than)	3.00%
Payment terms			75 days
Accounts receivable, allowance for credit loss	$ 4,032	$ 4,480	$ 4,032	$ 4,480	$ 3,279	$ 2,360	$ 4,672	$ 3,400
Contra seller payable	2,200		2,200			$ 1,500
Increase (decrease) in provision for expected credit losses	342	(274)	852	1,854
Increase (decrease) in contra seller payable	0	(300)	(600)	1,800
Provision for doubtful accounts	$ 400	$ 0	$ 217	$ 31

Revenue - Revenue Recognized on a Gross and Net Basis (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Revenue	$ 131,871	$ 60,982	$ 307,127	$ 139,625
Net basis
Disaggregation of Revenue [Line Items]
Revenue	105,866	59,913	258,236	138,063
Gross basis
Disaggregation of Revenue [Line Items]
Revenue	$ 26,005	$ 1,069	$ 48,891	$ 1,562
Revenue Benchmark \| Concentration of Basis of Revenue Recognition
Disaggregation of Revenue [Line Items]
Concentration risk, percentage	100.00%	100.00%	100.00%	100.00%
Revenue Benchmark \| Concentration of Basis of Revenue Recognition \| Net basis
Disaggregation of Revenue [Line Items]
Concentration risk, percentage	80.00%	98.00%	84.00%	99.00%
Revenue Benchmark \| Concentration of Basis of Revenue Recognition \| Gross basis
Disaggregation of Revenue [Line Items]
Concentration risk, percentage	20.00%	2.00%	16.00%	1.00%

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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+ Details

Revenue - Revenue Disaggregated by Sales Distribution Channel (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Revenue	$ 131,871	$ 60,982	$ 307,127	$ 139,625
CTV
Disaggregation of Revenue [Line Items]
Revenue	57,885	11,059	115,040	18,978
Desktop
Disaggregation of Revenue [Line Items]
Revenue	30,573	20,901	80,166	51,468
Mobile
Disaggregation of Revenue [Line Items]
Revenue	$ 43,413	$ 29,022	$ 111,921	$ 69,179
Product Concentration Risk \| Revenue Benchmark
Disaggregation of Revenue [Line Items]
Concentration risk, percentage	100.00%	100.00%	100.00%	100.00%
Product Concentration Risk \| Revenue Benchmark \| CTV
Disaggregation of Revenue [Line Items]
Concentration risk, percentage	44.00%	18.00%	38.00%	14.00%
Product Concentration Risk \| Revenue Benchmark \| Desktop
Disaggregation of Revenue [Line Items]
Concentration risk, percentage	23.00%	34.00%	26.00%	37.00%
Product Concentration Risk \| Revenue Benchmark \| Mobile
Disaggregation of Revenue [Line Items]
Concentration risk, percentage	33.00%	48.00%	36.00%	49.00%

- Definition

+ References

+ Details

Revenue - Revenue Disaggregated by Geographic Location (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Revenue	$ 131,871	$ 60,982	$ 307,127	$ 139,625
United States
Disaggregation of Revenue [Line Items]
Revenue	104,633	45,048	237,844	101,168
International
Disaggregation of Revenue [Line Items]
Revenue	$ 27,238	$ 15,934	$ 69,283	$ 38,457

- Definition

+ References

+ Details

Revenue - Schedule of Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for doubtful accounts, Beginning Balance	$ 3,279	$ 4,672	$ 2,360	$ 3,400
Allowance for doubtful accounts, merger and acquisition-assumed	425	0	835	1,033
Write-offs	(14)	(1)	(35)	(1,897)
Increase (decrease) in provision for expected credit losses	342	(274)	852	1,854
Recoveries of previous write-offs	0	83	20	90
Allowance for doubtful accounts, September 30	$ 4,032	$ 4,480	$ 4,032	$ 4,480

Fair Value Measurements - Financial Instruments (Details) - Recurring - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 7,869	$ 7,868
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	7,869	7,868
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 0	$ 0

Fair Value Measurements - Narrative (Details) - Recurring - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 7,869	$ 7,868
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	$ 0
Convertible notes	$ 341,000

Other Balance Sheet Amounts - Accounts Payable and Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accounts payable—seller	$ 791,227	$ 492,605
Accounts payable—trade	15,321	4,268
Accrued employee-related payables	20,544	12,442
Accrued holdback - indemnification claims	1,409	0
Total	$ 828,501	$ 509,315

Other Balance Sheet Amounts - Narrative (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Restricted cash	$ 251	$ 100	$ 1,304

Goodwill, Intangible Assets, and Capitalized Costs Incurred in Cloud Computing Arrangements - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 972,747		$ 972,747		$ 158,125
Amortization expense of intangible assets	42,200	$ 7,800	79,300	$ 16,900
Prepaid Expenses and Other Current Assets
Acquired Finite-Lived Intangible Assets [Line Items]
Capitalized cloud computing software, net	500		500		200
Other Noncurrent Assets
Acquired Finite-Lived Intangible Assets [Line Items]
Capitalized cloud computing software, net	700		700		$ 700
Computer Software, Intangible Asset
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense of intangible assets	100		300
Capitalized computer software, additions	$ 100		$ 700

Goodwill, Intangible Assets, and Capitalized Costs Incurred in Cloud Computing Arrangements - Finite-Lived Intangible Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Total identifiable intangible assets, gross	$ 576,708	$ 123,708
Total accumulated amortization—intangible assets	(113,137)	(33,824)
Total	463,571	89,884
Developed technology
Finite-Lived Intangible Assets [Line Items]
Total identifiable intangible assets, gross	373,558	77,658
Total accumulated amortization—intangible assets	(57,282)	(21,905)
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Total identifiable intangible assets, gross	173,950	37,950
Total accumulated amortization—intangible assets	(47,359)	(11,877)
In-process research and development
Finite-Lived Intangible Assets [Line Items]
Total identifiable intangible assets, gross	14,630	8,030
Total accumulated amortization—intangible assets	(449)	0
Backlog
Finite-Lived Intangible Assets [Line Items]
Total identifiable intangible assets, gross	11,100	0
Total accumulated amortization—intangible assets	(6,938)	0
Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Total identifiable intangible assets, gross	2,070	70
Total accumulated amortization—intangible assets	(756)	(42)
Trademarks
Finite-Lived Intangible Assets [Line Items]
Total identifiable intangible assets, gross	1,400	0
Total accumulated amortization—intangible assets	$ (353)	$ 0

Goodwill, Intangible Assets, and Capitalized Costs Incurred in Cloud Computing Arrangements - Finite-Lived Intangible Assets, Future Amortization Expense (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fiscal Year
Remaining 2021	$ 42,527
2022	147,361
2023	101,996
2024	84,218
2025	66,668
Thereafter	20,801
Total	$ 463,571	$ 89,884

Business Combinations - Telaria Unaudited Pro forma Information (Details) - Telaria $ in Thousands	9 Months Ended
	Sep. 30, 2020 USD ($)
Business Acquisition [Line Items]
Pro Forma Revenue	$ 154,663
Pro Forma Net Loss	$ (69,706)

Business Combinations - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands				3 Months Ended		9 Months Ended		12 Months Ended
	Jul. 01, 2021	Apr. 30, 2021	Feb. 04, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Apr. 29, 2021
Business Acquisition [Line Items]
Share Price (in USD per share)		$ 40.05							$ 49.21
Acquisition related costs				$ 2,424	$ 2,254	$ 37,778	$ 16,677
SpotX, Inc \| SpringServe
Business Acquisition [Line Items]
Prior investment								$ 2,100
Fair value of prior investment	$ 9,500	$ 7,500
SpotX and SpringServe
Business Acquisition [Line Items]
Deferred tax liabilities estimated tax rate		26.30%
SpotX, Inc
Business Acquisition [Line Items]
Cash Consideration		$ 640,000	$ 560,000
Issued in merger (in shares)		12,374,315	14,000,000
Cash consideration, elected increase, percent		20.00%
Cash consideration, elected increase, amount		$ 80,000
Shares issued, elected decrease, percent		20.00%
Shares issued, elected decrease, value		$ 80,000
Purchase price prior to working capital adjustments		1,100,000
Working capital adjustment		65,152
Purchase price		1,200,743	$ 1,200,000
Stock Consideration (Fair Value of Shares of Magnite common stock)		495,591
Deferred tax liabilities		$ 113,000
Deferred tax asset valuation allowance decrease						56,200
Acquisition related costs				800		27,900
SpringServe
Business Acquisition [Line Items]
Cash Consideration	31,136
Deferred tax liabilities	6,200
Acquisition related costs				$ 0		$ 0
Purchase price held back to cover possible indemnification claims	$ 1,400

Business Combinations - SpotX Purchase Consideration (Details) - SpotX, Inc - USD ($) $ in Thousands	Apr. 30, 2021	Feb. 04, 2021
Business Acquisition [Line Items]
Cash Consideration	$ 640,000	$ 560,000
Stock Consideration (Fair Value of Shares of Magnite common stock)	495,591
Working capital adjustment	65,152
Total purchase consideration	$ 1,200,743	$ 1,200,000

Business Combinations - SpotX Schedule of Recognized Identified Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Apr. 30, 2021	Dec. 31, 2020
Business Acquisition [Line Items]
Goodwill	$ 972,747		$ 158,125
SpotX, Inc
Business Acquisition [Line Items]
Cash		$ 81,967
Restricted cash		199
Accounts receivable		199,649
Prepaid and other assets, current		12,308
Fixed assets		5,093
Intangible assets		429,600
Right-of-use lease asset		11,785
Goodwill		790,466
Total assets to be acquired		1,531,067
Accounts payable and accrued expenses		205,913
Other current liabilities		7,169
Lease liabilities		12,625
Deferred tax liability, net		104,617
Total liabilities to be assumed		330,324
Total purchase price		$ 1,200,743

Business Combinations - SpotX Components of Intangible Assets and Estimated Useful Lives (Details) - SpotX, Inc $ in Thousands	Apr. 30, 2021 USD ($) project
Business Acquisition [Line Items]
Intangible assets acquired	$ 429,600
Technology
Business Acquisition [Line Items]
Intangible assets acquired	$ 280,400
Weighted-average useful life	5 years
Customer relationships
Business Acquisition [Line Items]
Intangible assets acquired	$ 130,300
Customer relationships \| Minimum
Business Acquisition [Line Items]
Weighted-average useful life	2 years
Customer relationships \| Maximum
Business Acquisition [Line Items]
Weighted-average useful life	4 years
Backlog
Business Acquisition [Line Items]
Intangible assets acquired	$ 11,100
Weighted-average useful life	1 year
In-process research and development
Business Acquisition [Line Items]
Intangible assets acquired	$ 5,800
Number of projects \| project	6
Weighted-average useful life	3 years
Non-compete agreements
Business Acquisition [Line Items]
Intangible assets acquired	$ 1,500
Weighted-average useful life	1 year
Trademarks
Business Acquisition [Line Items]
Intangible assets acquired	$ 500
Weighted-average useful life	1 year

Business Combinations - SpringServe Purchase Consideration (Details) - USD ($) $ in Thousands		9 Months Ended
	Jul. 01, 2021	Sep. 30, 2021	Sep. 30, 2020
Business Acquisition [Line Items]
Indemnification claims - holdback		$ 1,409	$ 0
SpringServe
Business Acquisition [Line Items]
Cash Consideration	$ 31,136
SpotX initial cash investment in SpringServe	2,075
Fair value appreciation of SpotX purchase right	7,450
Indemnification claims - holdback	1,409
Total purchase consideration	$ 42,070

Business Combinations - SpringServe Schedule of Recognized Identified Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Jul. 01, 2021	Dec. 31, 2020
Business Acquisition [Line Items]
Goodwill	$ 972,747		$ 158,125
SpringServe
Business Acquisition [Line Items]
Cash		$ 1,062
Accounts receivable		3,234
Prepaid and other assets, current		157
Fixed assets		25
Intangible assets		23,400
Right-of-use lease asset		1,879
Goodwill		24,156
Total assets to be acquired		53,913
Accounts payable and accrued expenses		2,475
Other current liabilities		35
Lease liabilities		3,179
Deferred tax liability, net		6,154
Total liabilities to be assumed		11,843
Total purchase price		$ 42,070

Business Combinations - SpringServe Components of Intangible Assets and Estimated Useful Lives (Details) - SpringServe $ in Thousands	Jul. 01, 2021 USD ($) project
Business Acquisition [Line Items]
Intangible assets acquired	$ 23,400
Technology
Business Acquisition [Line Items]
Intangible assets acquired	$ 15,500
Weighted-average useful life	5 years
Customer relationships
Business Acquisition [Line Items]
Intangible assets acquired	$ 5,700
Weighted-average useful life	2 years
Trademarks and Trade Names
Business Acquisition [Line Items]
Intangible assets acquired	$ 900
Weighted-average useful life	3 years
In-process research and development
Business Acquisition [Line Items]
Intangible assets acquired	$ 800
Weighted-average useful life	3 years
Number of projects \| project	2
Non-compete agreements
Business Acquisition [Line Items]
Intangible assets acquired	$ 500
Weighted-average useful life	2 years

Business Combinations - SpotX and SpringServe Unaudited Pro Forma Information (Details) - SpotX and SpringServe - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Business Acquisition [Line Items]
Pro Forma Revenue	$ 104,249	$ 379,180	$ 243,781
Pro Forma Net Loss	$ (29,651)	$ (88,187)	$ (157,803)

Merger, Acquisition, and Restructuring Costs - Merger and Restructuring Cost Activity (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Restructuring Cost and Reserve [Line Items]
Professional services (investment banking advisory, legal and other professional services)	$ 1,064	$ 952	$ 28,032	$ 9,533
Non-cash stock-based compensation (double-trigger acceleration and severance)	48	354	1,070	1,554
Total merger, acquisition, and restructuring costs	2,424	2,254	37,778	16,677
Personnel related (severance and one-time termination benefit costs)
Restructuring Cost and Reserve [Line Items]
Restructuring charges	1,312	948	6,176	5,590
Loss contracts (lease related)
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 0	$ 0	$ 2,500	$ 0

Merger, Acquisition, and Restructuring Costs - Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
SpotX Acquisition, SpringServe Acquisition, And Telaria Merger
Business Acquisition [Line Items]
Accrued merger, acquisition, and restructuring costs	$ 4.1	$ 2.9

Merger, Acquisition, and Restructuring Costs - Accrued Merger and Restructuring Cost Activity (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Restructuring Reserve [Roll Forward]
Non-cash stock-based compensation	$ (48)	$ (354)	$ (1,070)	$ (1,554)
SpotX and Telaria
Restructuring Reserve [Roll Forward]
Accrued merger, acquisition, and restructuring costs at December 31, 2020			2,935
Restructuring costs, personnel related and non-cash stock-based compensation			7,246
Restructuring activity, merger and acquisition loss contracts			2,500
Cash paid for restructuring costs			(5,035)
Non-cash loss contracts (lease related)			(2,500)
Non-cash stock-based compensation			(1,070)
Accrued merger, acquisition, and restructuring costs at September 30, 2021	$ 4,076		$ 4,076

Stock-Based Compensation - Narrative (Details)	9 Months Ended
Stock-Based Compensation - Narrative (Details)	Sep. 30, 2021 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant (in shares)	12,968,404
Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
Stock Option \| Tranche one
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	1 year
Award vesting rights, percentage	25.00%
RSAs and RSUs \| Tranche one
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	1 year
Award vesting rights, percentage	25.00%
Restricted Stock Units (RSUs) \| Tranche two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, percentage	50.00%
RSUs granted (in shares)	300,000

Stock-Based Compensation - Stock Options Outstanding (Details) $ / shares in Units, shares in Thousands, $ in Thousands	9 Months Ended
	Sep. 30, 2021 USD ($) $ / shares shares
Shares Under Option
Beginning balance (in shares) \| shares	6,695
Granted (in shares) \| shares	302
Exercised (in shares) \| shares	(1,393)
Forfeited (in shares) \| shares	(306)
Ending balance (in shares) \| shares	5,298
Exercisable (in shares) \| shares	3,768
Weighted- Average Exercise Price
Beginning balance (usd per share) \| $ / shares	$ 5.61
Granted (usd per share) \| $ / shares	38.99
Exercised (usd per share) \| $ / shares	6.28
Forfeited (usd per share) \| $ / shares	8.87
Ending balance (usd per share) \| $ / shares	7.15
Exercisable (usd per share) \| $ / shares	$ 5.51
Weighted- Average Contractual Life
Outstanding	5 years 9 months 14 days
Exercisable	4 years 9 months 25 days
Aggregate Intrinsic Value
Outstanding \| $	$ 113,430
Exercisable \| $	$ 84,758

Stock-Based Compensation - Stock Options Narrative (Details) - Stock Option $ / shares in Units, $ in Millions	9 Months Ended
	Sep. 30, 2021 USD ($) $ / shares
Number of Shares
Intrinsic values of options exercised	$ 43.4
Unrecognized employee stock-based compensation	$ 9.6
Unrecognized employee stock-based compensation, period for recognition	2 years 2 months 12 days
Fair value of options vested in period	$ 3.3
Grant date fair value of options granted (usd per share) \| $ / shares	$ 24.57

Stock-Based Compensation - Valuation Assumptions (Details) - Stock Option	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	5 years	6 years 3 months 18 days	5 years	6 years 3 months 18 days
Risk-free interest rate	0.90%	0.33%	0.88%	0.45%
Expected volatility	79.00%	68.00%	79.00%	67.00%
Dividend yield	0.00%	0.00%	0.00%	0.00%

Stock-Based Compensation - Restricted Stock Units Activity (Details) - Restricted Stock Units (RSUs)	9 Months Ended
	Sep. 30, 2021 $ / shares shares
Number of Shares
Beginning balance (in shares)	7,450,000
Granted (in shares)	2,816,000
Canceled (in shares)	(779,000)
Vested and released (in shares)	(3,873,000)
Ending balance (in shares)	9,286,000
Restricted stock units outstanding and unvested (in shares)	7,413,000
Vested but deferred (in shares)	37,318
Weighted-Average Grant Date Fair Value
Beginning balance (in dollars per share) \| $ / shares	$ 5.30
Granted (in dollars per share) \| $ / shares	38.54
Canceled (in dollars per share) \| $ / shares	12.17
Vested and released (in dollars per share) \| $ / shares	5.21
Ending balance (in dollars per share) \| $ / shares	17.19
Restricted stock units outstanding and unvested (in dollars per share) \| $ / shares	$ 17.24

Stock-Based Compensation - Restricted Stock Units Narrative (Details) - Restricted Stock Units (RSUs) $ / shares in Units, $ in Millions	9 Months Ended
	Sep. 30, 2021 USD ($) $ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in dollars per share) \| $ / shares	$ 38.54
Fair value of restricted stock vested	$ 126.1
Intrinsic value of nonvested unit	208.6
Unrecognized employee stock-based compensation	$ 112.0
Unrecognized employee stock-based compensation, period for recognition	2 years 6 months

Stock-Based Compensation - Performance Stock Units Narrative (Details) $ / shares in Units, $ in Thousands	1 Months Ended			3 Months Ended		9 Months Ended
	Aug. 31, 2021 USD ($) day $ / shares shares	Apr. 30, 2021 USD ($) $ / shares shares	Apr. 30, 2020 USD ($) $ / shares shares	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense				$ 11,824	$ 7,350	$ 28,521	$ 21,298
Performance Shares Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense				$ 400		$ 700
Performance measurement percentage				100.00%		100.00%
Performance Shares Units \| Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares) \| shares	379,635	26,291	146,341
Fair value of restricted stock vested		$ 1,400	$ 900
Vested (in dollars per share) \| $ / shares		$ 52.49	$ 6.15
Trailing consecutive trading day performance period \| day	60
Performance Shares Units \| Tranche one \| Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of units granted	$ 3,000
Grant date fair value (in dollars per share) \| $ / shares	$ 23.94
Unrecognized employee stock-based compensation				$ 2,900		$ 2,900
Unrecognized employee stock-based compensation, period for recognition						2 years 10 months 24 days
Vesting period	3 years
Vesting, stock price trigger (in dollars per share) \| $ / shares	$ 60.00
Performance Shares Units \| Tranche two \| Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of units granted	$ 2,800
Grant date fair value (in dollars per share) \| $ / shares	$ 21.93
Unrecognized employee stock-based compensation				2,700		$ 2,700
Unrecognized employee stock-based compensation, period for recognition						3 years 10 months 24 days
Vesting period	4 years
Vesting, stock price trigger (in dollars per share) \| $ / shares	$ 80.00
Performance Shares Units \| Tranche three \| Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of units granted	$ 2,600
Grant date fair value (in dollars per share) \| $ / shares	$ 20.30
Unrecognized employee stock-based compensation				$ 2,500		$ 2,500
Unrecognized employee stock-based compensation, period for recognition						4 years 10 months 24 days
Vesting period	5 years
Vesting, stock price trigger (in dollars per share) \| $ / shares	$ 100.00
Performance Shares Units \| Minimum \| Vesting on third anniversary \| Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, percentage						0.00%
Performance Shares Units \| Minimum \| Tranche one \| Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, percentage						0.00%
Performance Shares Units \| Minimum \| Tranche two \| Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, percentage						0.00%
Performance Shares Units \| Minimum \| Tranche three \| Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, percentage						0.00%
Performance Shares Units \| Maximum \| Vesting on third anniversary \| Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, percentage						150.00%
Performance Shares Units \| Maximum \| Tranche one \| Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, percentage						100.00%
Performance Shares Units \| Maximum \| Tranche two \| Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, percentage						100.00%
Performance Shares Units \| Maximum \| Tranche three \| Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, percentage						100.00%
Performance Shares, Granted April 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance measurement percentage				150.00%		150.00%
Performance Shares, Granted April 2020 \| Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized employee stock-based compensation				$ 500		$ 500
Unrecognized employee stock-based compensation, period for recognition						1 year 6 months
Performance shares, Granted April 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance measurement percentage				0.00%		0.00%
Performance shares, Granted April 2021 \| Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized employee stock-based compensation				$ 1,200		$ 1,200
Unrecognized employee stock-based compensation, period for recognition						2 years 6 months

Stock-Based Compensation - Employee Stock Purchase Plan Narrative (Details) - shares	1 Months Ended
	Nov. 30, 2013	Sep. 30, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares reserved		12,968,404
2014 Employee Stock Purchase Plan \| Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum employee subscription rate	10.00%
Offering period	6 months
Purchase price of common stock, percent	85.00%
Number of shares reserved		3,068,352
Annual percentage increase	1.00%

Stock-Based Compensation - Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 11,824	$ 7,350	$ 28,521	$ 21,298
Cost of revenue
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	278	122	530	412
Sales and marketing
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	4,583	2,309	10,426	5,928
Technology and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	3,828	2,061	8,195	5,469
General and administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	3,087	2,504	8,299	7,935
Merger, acquisition, and restructuring costs
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 48	$ 354	$ 1,071	$ 1,554

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
Income Taxes (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Valuation Allowance [Line Items]
Provision (benefit) for income taxes	$ (4,708)	$ 446	$ (92,237)	$ 533
SpotX, Inc
Valuation Allowance [Line Items]
Deferred tax asset valuation allowance decrease			$ 56,200

- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References + Details

Lease Obligations - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Lessee, Lease, Description [Line Items]
Lease expense	$ 4,900	$ 3,700	$ 15,700	$ 9,700
Short-term lease expense	400	400	1,000	800
Sublease income	$ 1,000	1,200	$ 3,300	2,500
Weighted average discount rate	5.05%		5.05%
Weighted average remaining lease term	6 years 4 months 2 days		6 years 4 months 2 days
Minimum
Lessee, Lease, Description [Line Items]
Term of lease contract	1 year		1 year
Maximum
Lessee, Lease, Description [Line Items]
Term of lease contract	10 years		10 years
Loss contracts (lease related)
Lessee, Lease, Description [Line Items]
Restructuring charges	$ 0	0	$ 2,500	0
Data centers for cloud-based services
Lessee, Lease, Description [Line Items]
Variable lease cost	$ 9,900	$ 5,600	$ 24,600	$ 14,000

Lease Obligations - Schedule of Lease Liability Maturities (Details) $ in Thousands	Sep. 30, 2021 USD ($)
Fiscal Year
Remaining 2021	$ 4,093
2022	18,645
2023	15,193
2024	12,868
2025	7,286
Thereafter	25,921
Total lease payments (undiscounted)	84,006
Less: imputed interest	(12,974)
Lease liabilities—total (discounted)	$ 71,032

Commitments and Contingencies (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Financial Standby Letter of Credit
Other Commitments [Line Items]
Letters of credit outstanding, amount	$ 5.1	$ 6.3

SVB Loan Agreement (Details) - Revolving Credit Facility - USD ($)	Sep. 30, 2021	Apr. 30, 2021	Sep. 25, 2020
Loan Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity			$ 60,000,000
Eligible accounts receivable			85.00%
Debt outstanding amount		$ 0
Loan Agreement Sublimit
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 10,000,000

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References + Details

Convertible Senior Notes and Capped Call Transactions - Narrative (Details)	1 Months Ended	9 Months Ended
	Mar. 31, 2021 USD ($) day $ / shares	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Apr. 30, 2021 USD ($)
Debt Instrument [Line Items]
Net proceeds		$ 400,000,000	$ 0
Capped calls, transaction costs	$ 39,000,000
Debt issuance costs, gross	11,400,000			$ 27,700,000
Convertible Senior Notes
Debt Instrument [Line Items]
Capped calls, transaction costs	$ 39,000,000
Percent of outstanding balance holders able to call debt in the event of default	25.00%
Convertible Senior Notes \| Maximum
Debt Instrument [Line Items]
Conversion price (in USD per share) \| $ / shares	$ 91.2600
Convertible Senior Notes \| Minimum
Debt Instrument [Line Items]
Conversion price (in USD per share) \| $ / shares	$ 63.8818
Convertible Senior Notes \| Convertible Debt
Debt Instrument [Line Items]
Aggregate principle amount	$ 400,000,000
Interest rate	0.25%
Over-allotment options	$ 50,000,000
Net proceeds	$ 388,600,000
Conversion ratio	0.0156539
Convertible Senior Notes \| Convertible Debt \| Maximum
Debt Instrument [Line Items]
Make-whole fundamental change period	45 days
Convertible Senior Notes \| Convertible Debt \| Minimum
Debt Instrument [Line Items]
Make-whole fundamental change period	20 days
Convertible Senior Notes \| Convertible Debt \| Conversion Term (i)
Debt Instrument [Line Items]
Threshold percent of stock price trigger	130.00%
Threshold trading days \| day	20
Threshold consecutive trading days \| day	30
Convertible Senior Notes \| Convertible Debt \| Conversion Term (ii)
Debt Instrument [Line Items]
Threshold percent of stock price trigger	98.00%
Threshold trading days \| day	5
Threshold consecutive trading days \| day	10
Convertible Senior Notes \| Convertible Debt \| Conversion Term (iv)
Debt Instrument [Line Items]
Threshold percent of stock price trigger	130.00%
Threshold trading days \| day	20
Threshold consecutive trading days \| day	30

Convertible Senior Notes and Capped Call Transactions - Summary of Convertible Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Debt, non-current, net of debt issuance costs	$ 719,333	$ 0
Convertible Debt \| Convertible Senior Notes
Debt Instrument [Line Items]
Convertible Senior Notes	400,000
Unamortized debt issuance costs	(10,215)
Debt, non-current, net of debt issuance costs	$ 389,785

Convertible Senior Notes and Capped Call Transactions - Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2021	Sep. 30, 2020
Debt Instrument [Line Items]
Amortization of debt issuance costs		$ 3,223	$ 0
Convertible Debt \| Convertible Senior Notes
Debt Instrument [Line Items]
Contractual interest expense	$ 250	536
Amortization of debt issuance costs	572	1,227
Total interest expense	$ 822	$ 1,763
Effective interest rate	0.82%	0.82%

Convertible Senior Notes and Capped Call Transactions - Amortization of Debt Discount and Issuance Costs (Details) - Convertible Debt - Convertible Senior Notes $ in Thousands	Sep. 30, 2021 USD ($)
Debt Issuance Costs
Remaining 2021	$ 572
2022	2,288
2023	2,288
2024	2,288
2025	2,288
2026	491
Total	$ 10,215

Credit Facility - Narrative (Details) - USD ($)	Apr. 30, 2021	Sep. 30, 2021	Jun. 28, 2021	Mar. 31, 2021
Line of Credit Facility [Line Items]
Debt issuance costs, gross	$ 27,700,000			$ 11,400,000
Term Loan B Facility \| Secured Debt
Line of Credit Facility [Line Items]
Aggregate principle amount	$ 360,000,000
Long-term debt, term	7 years
Net proceeds	$ 325,000,000
Term Loan B Facility \| Secured Debt \| Debt Discount
Line of Credit Facility [Line Items]
Debt issuance costs, gross	10,800,000
Term Loan B Facility \| Secured Debt \| Deferred Financing Costs
Line of Credit Facility [Line Items]
Debt issuance costs, gross	$ 16,900,000
Term Loan B Facility \| Secured Debt \| Eurodollar
Line of Credit Facility [Line Items]
Variable interest rate	5.00%
Term Loan B Facility \| Secured Debt \| Alternate Base Rate
Line of Credit Facility [Line Items]
Variable interest rate	4.00%
Senior Secured Revolving Credit Facility \| Revolving Credit Facility
Line of Credit Facility [Line Items]
Debt utilization triggering leverage ratio compliance, percent	35.00%
Leverage ratio maximum	3.25
Available borrowing capacity		$ 59,900,000
Senior Secured Revolving Credit Facility \| Letter of Credit
Line of Credit Facility [Line Items]
Letters of credit outstanding, amount		$ 5,100,000
Senior Secured Revolving Credit Facility \| Eurodollar \| Minimum \| Revolving Credit Facility
Line of Credit Facility [Line Items]
Variable interest rate	4.25%
Senior Secured Revolving Credit Facility \| Eurodollar \| Maximum \| Revolving Credit Facility
Line of Credit Facility [Line Items]
Variable interest rate	4.75%
Senior Secured Revolving Credit Facility \| Alternate Base Rate \| Minimum \| Revolving Credit Facility
Line of Credit Facility [Line Items]
Variable interest rate	3.25%
Senior Secured Revolving Credit Facility \| Alternate Base Rate \| Maximum \| Revolving Credit Facility
Line of Credit Facility [Line Items]
Variable interest rate	3.75%
Senior Secured Revolving Credit Facility \| Revolving Credit Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 52,500,000		$ 65,000,000
Quarterly payments of principle balance (percent)	0.25%
Aggregate annual payments of principle balance (percent)	1.00%
Incremental Revolver \| Revolving Credit Facility
Line of Credit Facility [Line Items]
Increase in maximum borrowing capacity			12,500,000
Incremental Revolver \| Letter of Credit
Line of Credit Facility [Line Items]
Increase in maximum borrowing capacity			$ 5,000,000

Credit Facility - Summary of Term B Facility (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Debt, non-current, net of debt issuance costs	$ 719,333	$ 0
Secured Debt \| Term Loan B Facility
Debt Instrument [Line Items]
Term Loan B Facility	359,100
Unamortized debt issuance costs	(10,136)
Unamortized debt issuance costs	(15,816)
Debt, non-current, net of debt issuance costs	$ 333,148

Credit Facility - Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2021	Sep. 30, 2020
Debt Instrument [Line Items]
Amortization of debt issuance costs		$ 3,223	$ 0
Secured Debt \| Term Loan B Facility
Debt Instrument [Line Items]
Contractual interest expense	$ 5,290	8,798
Amortization of debt discount	399	664
Amortization of debt issuance costs	622	1,036
Total interest expense	$ 6,311	$ 10,498
Effective interest rate	7.00%	7.00%

Credit Facility - Amortization of Debt Discount and Issuance Costs (Details) - Secured Debt - Term Loan B Facility $ in Thousands	Sep. 30, 2021 USD ($)
Debt Discount
Remaining 2021	$ 398
2022	1,580
2023	1,564
2024	1,548
2025	1,532
Thereafter	3,514
Total	10,136
Debt Issuance Costs
Remaining 2021	620
2022	2,466
2023	2,441
2024	2,416
2025	2,391
Thereafter	5,482
Total	$ 15,816

Subsequent Events (Details) - USD ($) $ in Millions		1 Months Ended	9 Months Ended
Subsequent Events (Details) - USD ($) $ in Millions	Oct. 20, 2021	Nov. 03, 2021	Sep. 30, 2021
Restricted stock units
Subsequent Event [Line Items]
Granted (in shares)			2,816,000
Restricted stock units \| Tranche two
Subsequent Event [Line Items]
Award vesting rights, percentage			50.00%
Subsequent Events
Subsequent Event [Line Items]
Minimum commitment amount		$ 2.2
Commitment period		3 years
Subsequent Events \| Restricted stock units
Subsequent Event [Line Items]
Granted (in shares)	91,582
Subsequent Events \| Restricted stock units \| Tranche one
Subsequent Event [Line Items]
Granted (in shares)	25,557
Subsequent Events \| Restricted stock units \| Tranche one, vesting over four years
Subsequent Event [Line Items]
Vesting period	4 years
Subsequent Events \| Restricted stock units \| Tranche one, vesting over one year
Subsequent Event [Line Items]
Vesting period	1 year
Award vesting rights, percentage	25.00%
Subsequent Events \| Restricted stock units \| Tranche two
Subsequent Event [Line Items]
Granted (in shares)	66,025
Subsequent Events \| Restricted stock units \| Tranche two, vesting October 1, 2022
Subsequent Event [Line Items]
Award vesting rights, percentage	50.00%
Subsequent Events \| Restricted stock units \| Tranche two, vesting October 1, 2023
Subsequent Event [Line Items]
Award vesting rights, percentage	50.00%