Cover - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2022	Jan. 31, 2023	Jun. 30, 2022
Document Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2022
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-38211
Entity Registrant Name	ROKU, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	26-2087865
Entity Address, Address Line One	1155 Coleman Avenue
Entity Address, City or Town	San Jose
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	95110
City Area Code	408
Local Phone Number	556-9040
Title of 12(b) Security	Class A Common Stock, $0.0001 par value
Trading Symbol	ROKU
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 9.9
Documents Incorporated by Reference	Part III incorporates by reference certain information from the Registrant’s definitive proxy statement (the “Proxy Statement”) for the 2023 Annual Meeting of Stockholders. The Proxy Statement will be filed with the Securities and Exchange Commission within 120 days of the registrant’s fiscal year ended December 31, 2022.
Amendment Flag	false
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	FY
Entity Central Index Key	0001428439
Class A Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		122,684,437
Class B Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		17,424,911