Who owns Magnite, Inc. (MGNI)
Which tracked institutional funds hold MGNI, how they are positioned, and who is buying versus exiting — from SEC Form 13F-HR filings. See MGNI company fundamentals →
Ownership as of the 2026-Q1 13F filings (latest filed 2026-05-18). 13F is disclosed up to 45 days after quarter-end, so the most recent quarter fills in over the following weeks.
How the tape is positioned
49 tracked funds added or opened MGNI while 113 trimmed or exited it between 2025-Q4 and 2026-Q1 — the tape is split. When large holders disagree on a name, the funds moving first are sometimes ahead of the story.
A prompt to read the filings, not a verdict. 13F is a quarter-end snapshot disclosed up to 45 days late; a fund adds or exits for mandate, benchmark, and timing reasons that have nothing to do with a view on the stock. This is a starting question, not a signal to trade.
Conviction spread
MGNI’s largest tracked holder by dollar value, VANGUARD GROUP INC, sizes it at 0.0% of its own reported 13F book, while the median holder sizes it at 0.0% of theirs — a 0.0pp gap the other way — the median holder sizes MGNI more heavily than its largest holder by dollar value does.
Book-share is each fund’s reported value in MGNI divided by its whole reported 13F book, so it is comparable across funds of different sizes and is unaffected by stock splits. A higher share means a fund has committed more of its book to the name — a starting question about conviction, not a verdict or a signal to trade.
Institutional & insider positioning
Between 2025-Q4 and 2026-Q1, across 297 tracked filers holding MGNI, 167 increased or opened the position and 139 reduced or closed it; over the same quarter, open-market insider Form 4 buying and selling roughly offset.
This fuses two public signals for the same quarter — how tracked institutions changed their positions and whether insiders bought or sold in the open market. It describes what was filed; it is a starting question, not a verdict or a signal to trade.
New buyers & exits
Funds opening or closing a position in MGNI between the 2025-Q4 and 2026-Q1 13F filings, and the largest changes among funds holding it in both. New buyers and exits are counted on fund presence (split-invariant); adds and trims are measured on reported value.
New buyers 19
- VANGUARD PORTFOLIO MANAGEMENT LLC$92M
- VANGUARD CAPITAL MANAGEMENT LLC$74M
- VANGUARD FIDUCIARY TRUST CO$12M
- Park West Asset Management LLC$7M
- Capital World Investors$5M
- Lisanti Capital Growth, LLC$4M
Full exits 21
- VANGUARD GROUP INC$221M
- Stephens Investment Management Group LLC$18M
- FRONTIER CAPITAL MANAGEMENT CO LLC$15M
- J. Goldman & Co LP$13M
- Penn Capital Management Company, LLC$11M
- Apis Capital Advisors, LLC$10M
Largest adds
- MILLENNIUM MANAGEMENT LLC$14M
- JANE STREET GROUP, LLC$14M
- VICTORY CAPITAL MANAGEMENT INC$13M
- Schonfeld Strategic Advisors LLC$6M
- GRIZZLYROCK CAPITAL, LLC$5M
- Qube Research & Technologies Ltd$5M
Largest trims
- Capital Research Global Investors$150M
- FMR LLC$55M
- BlackRock, Inc.$50M
- WELLINGTON MANAGEMENT GROUP LLP$32M
- AMERICAN CENTURY COMPANIES INC$31M
- Granahan Investment Management, LLC$20M
Institutional holders
One row per tracked fund, largest reported value first. “% of value” is the fund’s share of this security’s tracked institutional value — not of shares outstanding. Rows marked stale are from an earlier filing than the security’s latest quarter — that fund is absent from the newest snapshot (position exited, or reported under a different name).
| Fund | Shares | Reported value | % of value | Quarter |
|---|---|---|---|---|
| BlackRock, Inc. added | 11,657,496 | $138M | 7.2% | 2026-Q1 |
| WELLINGTON MANAGEMENT GROUP LLP added | 9,126,621 | $108M | 5.7% | 2026-Q1 |
| VANGUARD PORTFOLIO MANAGEMENT LLC new | 7,726,205 | $92M | 4.8% | 2026-Q1 |
| VANGUARD CAPITAL MANAGEMENT LLC new | 6,190,403 | $74M | 3.8% | 2026-Q1 |
| Capital Research Global Investors trimmed | 5,020,289 | $60M | 3.1% | 2026-Q1 |
| Boston Partners added | 4,719,863 | $56M | 2.9% | 2026-Q1 |
| AMERICAN CENTURY COMPANIES INC trimmed | 4,626,816 | $55M | 2.9% | 2026-Q1 |
| FMR LLC trimmed | 4,504,234 | $54M | 2.8% | 2026-Q1 |
| DIMENSIONAL FUND ADVISORS LP added | 3,983,674 | $47M | 2.5% | 2026-Q1 |
| Nuveen, LLC added | 3,590,025 | $43M | 2.2% | 2026-Q1 |
| GEODE CAPITAL MANAGEMENT, LLC added | 3,553,790 | $42M | 2.2% | 2026-Q1 |
| Nine Ten Capital Management LLC added | 3,481,283 | $41M | 2.2% | 2026-Q1 |
| STATE STREET CORP added | 3,163,139 | $38M | 2.0% | 2026-Q1 |
| Edenbrook Capital, LLC added | 2,798,036 | $33M | 1.7% | 2026-Q1 |
| Granahan Investment Management, LLC trimmed | 2,553,413 | $30M | 1.6% | 2026-Q1 |
| Ophir Asset Management Pty Ltd trimmed | 2,118,016 | $25M | 1.3% | 2026-Q1 |
| 325 CAPITAL LLC | 2,005,387 | $24M | 1.2% | 2026-Q1 |
| KENNEDY CAPITAL MANAGEMENT LLC added | 1,753,542 | $21M | 1.1% | 2026-Q1 |
| JANE STREET GROUP, LLC added | 1,668,160 | $20M | 1.0% | 2026-Q1 |
| No Street GP LP added | 1,628,248 | $19M | 1.0% | 2026-Q1 |
| Schonfeld Strategic Advisors LLC added | 1,605,041 | $19M | 1.0% | 2026-Q1 |
| GOLDMAN SACHS GROUP INC trimmed | 1,500,852 | $18M | 0.9% | 2026-Q1 |
| BALYASNY ASSET MANAGEMENT L.P. added | 1,500,443 | $18M | 0.9% | 2026-Q1 |
| ROYCE & ASSOCIATES LP added | 1,365,489 | $16M | 0.8% | 2026-Q1 |
| Maestria Partners LLC | 1,363,505 | $16M | 0.8% | 2026-Q1 |
| Blue Grotto Capital, LLC trimmed | 1,328,782 | $16M | 0.8% | 2026-Q1 |
| NORTHERN TRUST CORP added | 1,322,571 | $16M | 0.8% | 2026-Q1 |
| VICTORY CAPITAL MANAGEMENT INC added | 1,266,522 | $15M | 0.8% | 2026-Q1 |
| GRIZZLYROCK CAPITAL, LLC added | 1,238,680 | $15M | 0.8% | 2026-Q1 |
| MILLENNIUM MANAGEMENT LLC added | 1,234,457 | $15M | 0.8% | 2026-Q1 |
| CHARLES SCHWAB INVESTMENT MANAGEMENT INC trimmed | 1,180,431 | $14M | 0.7% | 2026-Q1 |
| Bank of New York Mellon Corp trimmed | 1,138,217 | $14M | 0.7% | 2026-Q1 |
| BANK OF AMERICA CORP /DE/ added | 1,125,196 | $13M | 0.7% | 2026-Q1 |
| CITADEL ADVISORS LLC added | 1,052,908 | $13M | 0.7% | 2026-Q1 |
| VANGUARD FIDUCIARY TRUST CO new | 997,082 | $12M | 0.6% | 2026-Q1 |
| Meros Investment Management, LP added | 992,351 | $12M | 0.6% | 2026-Q1 |
| MORGAN STANLEY trimmed | 926,819 | $11M | 0.6% | 2026-Q1 |
| Kopion Asset Management, LLC added | 855,904 | $10M | 0.5% | 2026-Q1 |
| Man Group plc added | 663,957 | $8M | 0.4% | 2026-Q1 |
| Qube Research & Technologies Ltd added | 661,057 | $8M | 0.4% | 2026-Q1 |
| OBERWEIS ASSET MANAGEMENT INC/ added | 647,600 | $8M | 0.4% | 2026-Q1 |
| PICTON MAHONEY ASSET MANAGEMENT added | 643,078 | $8M | 0.4% | 2026-Q1 |
| SILVERCREST ASSET MANAGEMENT GROUP LLC trimmed | 616,084 | $7M | 0.4% | 2026-Q1 |
| Park West Asset Management LLC new | 598,380 | $7M | 0.4% | 2026-Q1 |
| NOMURA ASSET MANAGEMENT CO LTD trimmed | 593,900 | $7M | 0.4% | 2026-Q1 |
| CenterBook Partners LP added | 564,156 | $7M | 0.3% | 2026-Q1 |
| KING LUTHER CAPITAL MANAGEMENT CORP added | 531,066 | $6M | 0.3% | 2026-Q1 |
| JPMORGAN CHASE & CO trimmed | 486,868 | $6M | 0.3% | 2026-Q1 |
| Capital World Investors new | 456,672 | $5M | 0.3% | 2026-Q1 |
| QVT Financial LP added | 453,910 | $5M | 0.3% | 2026-Q1 |
| UBS Group AG added | 450,349 | $5M | 0.3% | 2026-Q1 |
| First Eagle Investment Management, LLC added | 450,288 | $5M | 0.3% | 2026-Q1 |
| PRINCIPAL FINANCIAL GROUP INC added | 445,950 | $5M | 0.3% | 2026-Q1 |
| NORDEA INVESTMENT MANAGEMENT AB trimmed | 421,008 | $5M | 0.3% | 2026-Q1 |
| Caption Management, LLC added | 405,053 | $5M | 0.3% | 2026-Q1 |
| S SQUARED TECHNOLOGY, LLC | 402,862 | $5M | 0.2% | 2026-Q1 |
| TWO SIGMA INVESTMENTS, LP added | 394,856 | $5M | 0.2% | 2026-Q1 |
| COMMONWEALTH EQUITY SERVICES, LLC added | 359,570 | $4M | 0.2% | 2026-Q1 |
| SEI INVESTMENTS CO added | 350,862 | $4M | 0.2% | 2026-Q1 |
| 1492 Capital Management LLC trimmed | 340,542 | $4M | 0.2% | 2026-Q1 |
| HARBOR CAPITAL ADVISORS, INC. added | 325,261 | $4M | 0.2% | 2026-Q1 |
| UBS AM, a distinct business unit of UBS ASSET MANAGEMENT AMERICAS LLC trimmed | 323,018 | $4M | 0.2% | 2026-Q1 |
| Manatuck Hill Partners, LLC trimmed | 310,000 | $4M | 0.2% | 2026-Q1 |
| Lisanti Capital Growth, LLC added | 309,440 | $4M | 0.2% | 2026-Q1 |
| SUSQUEHANNA INTERNATIONAL GROUP, LLP added | 307,805 | $4M | 0.2% | 2026-Q1 |
| ALLIANCEBERNSTEIN L.P. added | 223,191 | $4M | 0.2% | 2026-Q1 |
| Squarepoint Ops LLC added | 300,934 | $4M | 0.2% | 2026-Q1 |
| RAYMOND JAMES FINANCIAL INC trimmed | 291,715 | $3M | 0.2% | 2026-Q1 |
| Norwood Investment Partners, LP trimmed | 285,000 | $3M | 0.2% | 2026-Q1 |
| Swiss National Bank added | 284,300 | $3M | 0.2% | 2026-Q1 |
| ALGERT GLOBAL LLC trimmed | 269,035 | $3M | 0.2% | 2026-Q1 |
| VANGUARD GROUP INC trimmed | 13,610,776 | $221M | 11.5% | 2025-Q4 stale |
| Driehaus Capital Management LLC trimmed | 1,516,296 | $33M | 1.7% | 2025-Q3 stale |
| T. Rowe Price Investment Management, Inc. new | 890,918 | $19M | 1.0% | 2025-Q3 stale |
| Pacer Advisors, Inc. trimmed | 791,819 | $19M | 1.0% | 2025-Q2 stale |
| Stephens Investment Management Group LLC added | 1,128,578 | $18M | 1.0% | 2025-Q4 stale |
| FRONTIER CAPITAL MANAGEMENT CO LLC trimmed | 944,701 | $15M | 0.8% | 2025-Q4 stale |
| J. Goldman & Co LP trimmed | 782,837 | $13M | 0.7% | 2025-Q4 stale |
| Penn Capital Management Company, LLC trimmed | 694,766 | $11M | 0.6% | 2025-Q4 stale |
| Apis Capital Advisors, LLC trimmed | 604,000 | $10M | 0.5% | 2025-Q4 stale |
| Pillsbury Lake Capital LLC new | 583,644 | $9M | 0.5% | 2025-Q4 stale |
| INTRINSIC EDGE CAPITAL MANAGEMENT LLC added | 733,044 | $8M | 0.4% | 2025-Q1 stale |
| Granite Investment Partners, LLC trimmed | 720,873 | $8M | 0.4% | 2025-Q1 stale |
| VOLORIDGE INVESTMENT MANAGEMENT, LLC trimmed | 375,212 | $8M | 0.4% | 2025-Q3 stale |
| Roubaix Capital, LLC new | 260,735 | $6M | 0.3% | 2025-Q2 stale |
| CANNELL CAPITAL LLC added | 265,152 | $6M | 0.3% | 2025-Q3 stale |
| Alta Park Capital, LP trimmed | 255,698 | $6M | 0.3% | 2025-Q3 stale |
| Connor, Clark & Lunn Investment Management Ltd. trimmed | 225,281 | $5M | 0.3% | 2025-Q2 stale |
| Dilation Capital Management LP trimmed | 245,900 | $5M | 0.3% | 2025-Q3 stale |
| Informed Momentum Co LLC added | 241,943 | $5M | 0.3% | 2025-Q3 stale |
| Polar Asset Management Partners Inc. added | 213,866 | $5M | 0.2% | 2025-Q3 stale |
| D. E. Shaw & Co., Inc. added | 211,433 | $5M | 0.2% | 2025-Q3 stale |
| BANK OF MONTREAL /CAN/ added | 276,273 | $4M | 0.2% | 2025-Q4 stale |
| ARMISTICE CAPITAL, LLC new | 389,000 | $4M | 0.2% | 2025-Q1 stale |
| CASTLEARK MANAGEMENT LLC added | 193,185 | $4M | 0.2% | 2025-Q3 stale |
| Advantage Alpha Capital Partners LP trimmed | 160,447 | $3M | 0.2% | 2025-Q3 stale |
| AMERIPRISE FINANCIAL INC added | 150,495 | $3M | 0.2% | 2025-Q3 stale |
| EFG Asset Management (North America) Corp. trimmed | 150,511 | $3M | 0.2% | 2025-Q3 stale |
| AYAL Capital Advisors Ltd added | 200,000 | $3M | 0.2% | 2025-Q4 stale |
| FIRST TRUST ADVISORS LP trimmed | 199,872 | $3M | 0.2% | 2025-Q4 stale |
Ownership over time
Tracked institutional holder count and total shares held by filing quarter (independent scales). The curated-era tail and any mid-ingest latest quarter are handled honestly — a partial quarter is not drawn as a collapse.
Reading this table
Funds hold the same stock for different reasons — an index fund “holds” almost everything, an active manager sizes a name to a mandate and a benchmark, and each fund entered at its own price and time. Because 13F is filed up to 45 days after quarter-end, every row is a backward-looking snapshot; a manager may have traded since. Share-class siblings (a company’s A and C shares) are rolled up to one line so a dual-class name is never double-counted. Compare like-for-like. A large holder is not an endorsement, and a fund exiting is not a warning — this is a starting question, not a verdict.
About 13F filings
A Form 13F is a quarterly disclosure that institutional investment managers with over $100 million in US-listed equities must file with the SEC. In plain English: it is a snapshot of the long stock positions a fund held at the end of a quarter. It covers long US-listed equities only — not short positions, options, cash, or private holdings — and the funds shown are the large sample we track, not the complete 13F universe.