Cover Page - shares	6 Months Ended
	Jun. 30, 2023	Aug. 02, 2023
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2023
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	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		136,958,660
Entity Central Index Key	0001595974
Amendment Flag	false
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q2
Current Fiscal Year End Date	--12-31