Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities:
Net loss	$ (80,026)	$ (77,620)	$ (69,703)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	15,297	11,055	8,740
Amortization of deferred sales commissions	17,801	7,486	3,038
Stock-based compensation	34,680	31,618	8,963
Provision for doubtful accounts	326	182	642
Change in fair value of warrant liability	0	52	58
Other	0	0	95
Changes in operating assets and liabilities:
Accounts receivable	(27,000)	(19,632)	(10,578)
Prepaid expenses and other assets	(9,903)	(3,344)	(1,727)
Deferred contract costs	(36,508)	(18,943)	(10,685)
Accounts payable, accrued expenses and other liabilities	7,272	17,488	26,279
Content costs payable	4,389	6,615	3,113
Deferred revenue	66,568	54,667	25,310
Net cash provided by (used in) operating activities	(7,104)	9,624	(16,455)
Cash flows from investing activities:
Purchases of property and equipment	(5,335)	(5,180)	(3,328)
Capitalized software costs	(12,868)	(9,357)	(7,793)
Purchase of marketable securities	0	0	(1,542)
Proceeds from sale and maturity of marketable securities	0	0	27,274
Payments related to business combinations, net of cash acquired	(24,490)	0	0
Purchases of strategic investments	(10,000)	0	0
Net cash provided by (used in) investing activities	(52,693)	(14,537)	14,611
Cash flows from financing activities:
Net proceeds from exercise of stock options	10,878	10,383	11,265
Net proceeds from issuance of redeemable convertible preferred stock	2	120,710	0
Payment of redeemable convertible preferred stock issuance costs	(2,250)	0	0
Payment of deferred offering costs	(5,183)	0	0
Cash proceeds from initial public offering	415,187	0	0
Net cash provided by financing activities	418,634	131,093	11,265
Net increase in cash, cash equivalents and restricted cash	358,837	126,180	9,421
Cash, cash equivalents and restricted cash—Beginning of period	177,931	51,751	42,330
Cash, cash equivalents and restricted cash—End of period	536,768	177,931	51,751
Supplemental disclosures of cash flow information:
Interest paid	90	48	5
Income taxes paid	385	154	120
Supplemental disclosure of non-cash investing and financing activities:
Accrued redeemable convertible preferred stock issuance costs	0	2,250	0
Unpaid deferred offering costs	1,586	0	0
Stock-based compensation in capitalized costs	2,571	749	281
Increase (decrease) in purchases of property and equipment included in liabilities	(186)	131	76
Vesting of early-exercised stock options, net	0	7	421
Acquisition holdback liability	$ 1,500	$ 0	$ 0