| Cover | 12 Months Ended |
| Dec. 31, 2022 | |
| Cover [Abstract] | |
| Document Type | DEF 14A |
| Entity Registrant Name | MAGNITE, INC. |
| Entity Central Index Key | 0001595974 |
| Amendment Flag | false |
| Pay vs Performance Disclosure | 12 Months Ended | |||
| Dec. 31, 2022 USD ($) | Dec. 31, 2021 USD ($) | Dec. 31, 2020 USD ($) | ||
| Pay vs Performance Disclosure [Table] | ||||
| Pay vs Performance [Table Text Block] | Pay Versus Performance The following table sets forth additional compensation information of our Principal Executive Officer (PEO) and our other (non-PEO) NEOs along with total shareholder return, net income, and Total Revenue ex TAC performance results for our fiscal years 2020, 2021 and 2022. Investment of Initial Fixed $100 Investment Based on: Year (1) Summary (2) Compensation Actually Paid to PEO (3) (4) Average (2) Average (3) (5) Magnite’s (6) Peer Group (6) GAAP Total 1 Yr (7) (a) (b) (c) (d) (e) (f) (g) (h) (i) 2022 $6,128,497 -$3,532,121 $3,606,471 $1,383,790 $130 $77 -$130,323 24% 2021 $18,291,589 -$31,006 $7,113,462 $4,617,432 $214 $180 $65 90% 2020 $3,512,905 $33,894,891 $1,777,455 $12,699,997 $376 $193 -$53,432 40% | |||
| Company Selected Measure Name | Revenue ex-TAC Growth | |||
| Named Executive Officers, Footnote [Text Block] | (1) NEOs included in the above compensation columns reflect the following: Year PEO Non-PEO NEOs 2022 Mr. Barrett Messrs. Day Buckley Soroca Dove Ms. Evans 2021 Mr. Barrett Messrs. Day Buckley Dove Ms. Evans 2020 Mr. Barrett Messrs. Day , Kershaw Soroca Ms. Evans | |||
| Changed Peer Group, Footnote [Text Block] | Peer group TSR reflects the S&P Internet Select Industry Index performance as reflected in our Annual Report on Form 10-K for the fiscal year ended December 31, 2022 pursuant to Item 201(e) of Regulation S-K. For the Company and peer group TSR, each year reflects what the cumulative value of $100 would be, including reinvestment of dividends, if such amount were invested on December 31, 2019. | |||
| PEO Total Compensation Amount | $ 6,128,497 | $ 18,291,589 | $ 3,512,905 | |
| PEO Actually Paid Compensation Amount | $ (3,532,121) | (31,006) | 33,894,891 | |
| Adjustment To PEO Compensation, Footnote [Text Block] | (4) Compensation Actually Paid to PEO (Mr. Barrett) reflects the following adjustments from Total compensation reported in the Summary Compensation Table: 2020 2021 2022 Total Reported in Summary Compensation Table (SCT) $3,512,905 $18,291,589 $6,128,497 Less, value of Stock and Option Awards reported in SCT ($2,569,306) ($16,974,391) ($4,960,792) Plus, Year-End value of Awards Granted in Fiscal Year that are Unvested and Outstanding $18,245,564 $8,100,126 $3,679,620 Plus, Change in Fair Value of Prior Year Awards that are Outstanding and Unvested $14,583,801 ($9,233,914) ($6,440,676) Plus, FMV of Awards Granted this Year and that Vested this Year ($0) ($0) ($0) Plus, Change in Fair Value (from prior year-end) of Prior Year awards that Vested this year $121,927 ($214,416) ($1,938,770) Less Prior Year Fair Value of Prior Year awards that Failed to vest this year ($0) ($0) ($0) Plus, Value of Dividends or other Earnings Paid on Stock or Option Awards not Otherwise Reflected in Fair Value or Total Compensation ($0) ($0) ($0) Total Adjustments $30,381,986 ($18,322,595) ($9,660,618) Compensation Actually Paid $33,894,891 ($31,006) ($3,532,121) | |||
| Non-PEO NEO Average Total Compensation Amount | $ 3,606,471 | 7,113,462 | 1,777,455 | |
| Non-PEO NEO Average Compensation Actually Paid Amount | $ 1,383,790 | 4,617,432 | 12,699,997 | |
| Adjustment to Non-PEO NEO Compensation Footnote [Text Block] | (5) The average Compensation Actually Paid to the non-PEO NEOs reflects the following adjustments from Total compensation reported in the Summary Compensation Table: 2020 2021 2022 Total Reported in Summary Compensation Table (SCT) $1,777,455 $7,113,462 $3,606,471 Less, value of Stock and Option Awards reported in SCT ($1,121,444) ($2,991,280) ($2,212,933) Plus, Year-End value of Awards Granted in Fiscal Year that are Unvested and Outstanding $7,322,776 $1,475,824 $1,372,534 Plus, Change in Fair Value of Prior Year Awards that are Outstanding and Unvested (a) $4,611,689 ($1,498,220) ($552,353) Plus, FMV of Awards Granted this Year and that Vested this Year ($0) ($0) $75,793 Plus, Change in Fair Value (from prior year-end) of Prior Year awards that Vested this year (a) $109,521 $517,646 ($783,541) Less Prior Year Fair Value of Prior Year awards that Failed to vest this year ($0) ($0) ($122,181) Plus, Value of Dividends or other Earnings Paid on Stock or Option Awards not Otherwise Reflected in Fair Value or Total Compensation ($0) ($0) ($0) Total Adjustments $10,922,542 ($2,496,030) ($2,222,681) Compensation Actually Paid $12,699,997 $4,617,432 $1,383,790 (a) In 2020, there were legacy Telaria stock and option awards that the Company assumed as part of the Telaria merger on April 1, 2020 (“Assumed Awards”). These Assumed Awards were originally granted prior to 2020. For the table above, the change in fair value of Assumed Awards that remain outstanding and unvested in 2020 will be determined as the change in fair value from April 1, 2020 to December 31, 2020. Also, the change in fair value of Assumed Awards that vested in 2020 will be determined as the change in fair value from April 1, 2020 to vest date. | |||
| Compensation Actually Paid vs. Total Shareholder Return [Text Block] | ||||
| Compensation Actually Paid vs. Net Income [Text Block] | | |||
| Compensation Actually Paid vs. Company Selected Measure [Text Block] | | |||
| Tabular List [Table Text Block] | The following is a list of financial performance and non-financial performance measures, which in the Company’s assessment, represent the most important measures used by the Company to link compensation actually paid to the NEOs for 2022: Total Revenue ex-TAC Growth CTV Revenue ex-TAC Growth DV+ Revenue ex-TAC Growth Adjusted EBITDA less Capital Expenditures Relative Total Shareholder Return | |||
| Total Shareholder Return Amount | $ 130 | 214 | 376 | |
| Peer Group Total Shareholder Return Amount | 77 | 180 | 193 | |
| Net Income (Loss) | $ (130,323,000) | $ 65,000 | $ (53,432,000) | |
| Company Selected Measure Amount | 0.24 | 0.90 | 0.40 | |
| PEO Name | Mr. Barrett | Mr. Barrett | Mr. Barrett | |
| Measure [Axis]: 1 | ||||
| Pay vs Performance Disclosure [Table] | ||||
| Measure Name | Total Revenue ex-TAC Growth | |||
| Measure [Axis]: 2 | ||||
| Pay vs Performance Disclosure [Table] | ||||
| Measure Name | CTV Revenue ex-TAC Growth | |||
| Measure [Axis]: 3 | ||||
| Pay vs Performance Disclosure [Table] | ||||
| Measure Name | DV+ Revenue ex-TAC Growth | |||
| Measure [Axis]: 4 | ||||
| Pay vs Performance Disclosure [Table] | ||||
| Measure Name | Adjusted EBITDA less Capital Expenditures | |||
| Measure [Axis]: 5 | ||||
| Pay vs Performance Disclosure [Table] | ||||
| Measure Name | Relative Total Shareholder Return | |||
| Mr Barrett | ||||
| Pay vs Performance Disclosure [Table] | ||||
| PEO Total Compensation Amount | $ 6,128,497 | $ 18,291,589 | $ 3,512,905 | |
| PEO Actually Paid Compensation Amount | (3,532,121) | (31,006) | 33,894,891 | |
| Non-PEO NEO [Member] | Less, value of Stock and Option Awards reported in SCT | ||||
| Pay vs Performance Disclosure [Table] | ||||
| Adjustment to Compensation Amount | (2,212,933) | (2,991,280) | (1,121,444) | |
| Non-PEO NEO [Member] | Plus, Year-End value of Awards Granted in Fiscal Year that are Unvested and Outstanding | ||||
| Pay vs Performance Disclosure [Table] | ||||
| Adjustment to Compensation Amount | 1,372,534 | 1,475,824 | 7,322,776 | |
| Non-PEO NEO [Member] | Plus, Change in Fair Value of Prior Year Awards that are Outstanding and Unvested | ||||
| Pay vs Performance Disclosure [Table] | ||||
| Adjustment to Compensation Amount | [1] | (552,353) | (1,498,220) | 4,611,689 |
| Non-PEO NEO [Member] | Plus, FMV of Awards Granted this Year and that Vested this Year | ||||
| Pay vs Performance Disclosure [Table] | ||||
| Adjustment to Compensation Amount | 75,793 | 0 | 0 | |
| Non-PEO NEO [Member] | Plus, Change in Fair Value (from prior year-end) of Prior Year awards that Vested this year | ||||
| Pay vs Performance Disclosure [Table] | ||||
| Adjustment to Compensation Amount | [1] | (783,541) | 517,646 | 109,521 |
| Non-PEO NEO [Member] | Less Prior Year Fair Value of Prior Year awards that Failed to vest this year | ||||
| Pay vs Performance Disclosure [Table] | ||||
| Adjustment to Compensation Amount | (122,181) | 0 | 0 | |
| Non-PEO NEO [Member] | Plus, Value of Dividends or other Earnings Paid on Stock or Option Awards not Otherwise Reflected in Fair Value or Total Compensation | ||||
| Pay vs Performance Disclosure [Table] | ||||
| Adjustment to Compensation Amount | 0 | 0 | 0 | |
| Non-PEO NEO [Member] | Total Adjustments | ||||
| Pay vs Performance Disclosure [Table] | ||||
| Adjustment to Compensation Amount | $ (2,222,681) | $ (2,496,030) | $ 10,922,542 | |
| Non-PEO NEO [Member] | Messrs Day | ||||
| Pay vs Performance Disclosure [Table] | ||||
| PEO Name | Messrs. Day | Messrs. Day | Messrs. Day | |
| Non-PEO NEO [Member] | Buckley | ||||
| Pay vs Performance Disclosure [Table] | ||||
| PEO Name | Buckley | Buckley | ||
| Non-PEO NEO [Member] | Soroca | ||||
| Pay vs Performance Disclosure [Table] | ||||
| PEO Name | Soroca | Soroca | ||
| Non-PEO NEO [Member] | Dove | ||||
| Pay vs Performance Disclosure [Table] | ||||
| PEO Name | Dove | Dove | ||
| Non-PEO NEO [Member] | Ms Evans | ||||
| Pay vs Performance Disclosure [Table] | ||||
| PEO Name | Ms. Evans | Ms. Evans | Ms. Evans | |
| Non-PEO NEO [Member] | Kershaw | ||||
| Pay vs Performance Disclosure [Table] | ||||
| PEO Name | Kershaw | |||
| PEO [Member] | Mr Barrett | Less, value of Stock and Option Awards reported in SCT | ||||
| Pay vs Performance Disclosure [Table] | ||||
| Adjustment to Compensation Amount | $ (4,960,792) | $ (16,974,391) | $ (2,569,306) | |
| PEO [Member] | Mr Barrett | Plus, Year-End value of Awards Granted in Fiscal Year that are Unvested and Outstanding | ||||
| Pay vs Performance Disclosure [Table] | ||||
| Adjustment to Compensation Amount | 3,679,620 | 8,100,126 | 18,245,564 | |
| PEO [Member] | Mr Barrett | Plus, Change in Fair Value of Prior Year Awards that are Outstanding and Unvested | ||||
| Pay vs Performance Disclosure [Table] | ||||
| Adjustment to Compensation Amount | (6,440,676) | (9,233,914) | 14,583,801 | |
| PEO [Member] | Mr Barrett | Plus, FMV of Awards Granted this Year and that Vested this Year | ||||
| Pay vs Performance Disclosure [Table] | ||||
| Adjustment to Compensation Amount | 0 | 0 | 0 | |
| PEO [Member] | Mr Barrett | Plus, Change in Fair Value (from prior year-end) of Prior Year awards that Vested this year | ||||
| Pay vs Performance Disclosure [Table] | ||||
| Adjustment to Compensation Amount | (1,938,770) | (214,416) | 121,927 | |
| PEO [Member] | Mr Barrett | Less Prior Year Fair Value of Prior Year awards that Failed to vest this year | ||||
| Pay vs Performance Disclosure [Table] | ||||
| Adjustment to Compensation Amount | 0 | 0 | 0 | |
| PEO [Member] | Mr Barrett | Plus, Value of Dividends or other Earnings Paid on Stock or Option Awards not Otherwise Reflected in Fair Value or Total Compensation | ||||
| Pay vs Performance Disclosure [Table] | ||||
| Adjustment to Compensation Amount | 0 | 0 | 0 | |
| PEO [Member] | Mr Barrett | Total Adjustments | ||||
| Pay vs Performance Disclosure [Table] | ||||
| Adjustment to Compensation Amount | $ (9,660,618) | $ (18,322,595) | $ 30,381,986 | |
| [1]In 2020, there were legacy Telaria stock and option awards that the Company assumed as part of the Telaria merger on April 1, 2020 (“Assumed Awards”). These Assumed Awards were originally granted prior to 2020. For the table above, the change in fair value of Assumed Awards that remain outstanding and unvested in 2020 will be determined as the change in fair value from April 1, 2020 to December 31, 2020. Also, the change in fair value of Assumed Awards that vested in 2020 will be determined as the change in fair value from April 1, 2020 to vest date. | ||||
