Magnite, Inc.
Magnite, Inc. (MGNI) Stock Ownership
Institutional vs insider vs public ownership from 13F and float data — top holders, activity, and insider trades below.
SEC 13F · FMP · MGNI · as of Mar 31, 2025
Ownership Breakdown
318
Institutional Holders
▲ 5 vs Q4
$1.52B
Total Inst. Value
▼ $449.67M vs Q4
143.22M
Shares Outstanding
freeFloat 98.54%
132.91M
13F Shares Held
▲ 9.45M vs Q4
Institutional ownership = 13F shares ÷ total outstanding. Insider % = 100 − free float. Public % = free float − institution %. Data: FMP /symbol-positions-summary + /shares-float + SEC EDGAR.
Top Institutional Holders
MGNI largest shareholders · institutional ownership
Q1 2025 · SEC 13F
Showing top 10 holders
| Holder | Shares | % Owned | Weight | Value | Reported | Change |
|---|---|---|---|---|---|---|
VANGUARD GROUP INC services-computer programming, data processing, etc. | 13.74M | 9.69% | 9.69% | $156.81B | May 9, 2025 | ▲ 138.4K |
CAPITAL RESEARCH GLOBAL INVESTORS services-computer programming, data processing, etc. | 12.92M | 9.11% | 9.11% | $147.42B | May 12, 2025 | ▲ 5.19M |
BLACKROCK, INC. services-computer programming, data processing, etc. | 9.79M | 6.90% | 6.90% | $111.68B | May 2, 2025 | ▼ 379.4K |
FMR LLC services-computer programming, data processing, etc. | 9.68M | 6.83% | 6.83% | $110.50B | May 12, 2025 | ▲ 8.07M |
WELLINGTON MANAGEMENT GROUP LLP services-computer programming, data processing, etc. | 5.90M | 4.16% | 4.16% | $67.36B | May 13, 2025 | ▼ 1.13M |
DIMENSIONAL FUND ADVISORS LP services-computer programming, data processing, etc. | 5.28M | 3.72% | 3.72% | $60.27B | May 13, 2025 | ▼ 243.0K |
BOSTON PARTNERS services-computer programming, data processing, etc. | 5.28M | 3.72% | 3.72% | $60.19B | May 13, 2025 | ▲ 520.0K |
EDENBROOK CAPITAL, LLC services-computer programming, data processing, etc. | 4.02M | 2.83% | 2.83% | $45.83B | May 15, 2025 | ▲ 913.1K |
NUVEEN, LLC services-computer programming, data processing, etc. | 3.60M | 2.54% | 2.54% | $41.04B | May 12, 2025 | NEW |
GEODE CAPITAL MANAGEMENT, LLC services-computer programming, data processing, etc. | 3.03M | 2.14% | 2.14% | $34.62B | May 13, 2025 | ▲ 75.8K |
Data from SEC Form 13F filings. Ownership bar normalised to largest holder. Change flags: isNew / isSoldOut / changeInSharesNumber (FMP extract-analytics/holder).
Institutional Activity
Q1 2025 vs prior quarter
Q1 2025
21
Increased
+20.48M shares2
New Positions
first time holders27
Decreased
−9.11M shares0
Sold Out
fully exitedNet shares change (top 50)
+11.37M
+20.48M / −9.11M
Net new holders
-4
2 new / 0 exited
Based on top 50 institutional holders by position size. Fields: isNew, isSoldOut, changeInSharesNumber (FMP extract-analytics/holder, limit=50).
Insider Buying vs Selling
MGNI insider trading · insider activity
Source: SEC Form 4
Insiders have been primarily selling shares recently. Selling may be driven by pre-scheduled Rule 10b5-1 plans rather than negative sentiment.
0
Buy transactions
8
Sell transactions
0.00
Buy/Sell ratio
$0M
Total disposed
Recent Insider Transactions
Showing 10 most recent · Common Stock only
| Name · Role | Date | Type | Shares | Price | Value | After Trans. | Filing |
|---|---|---|---|---|---|---|---|
Spillane Robert F director | May 19, 2026 | Sale | 10,000 | $13.33 | $133.3K | 43.9K | Form 4 ↗ |
BARRETT MICHAEL G. CEO | May 15, 2026 | Tax Withhold | 10,404 | $12.82 | $133.4K | 403.1K | Form 4 ↗ |
Buckley Sean Patrick President, Revenue | May 15, 2026 | Tax Withhold | 12,019 | $12.82 | $154.1K | 392.7K | Form 4 ↗ |
Evans Katie Seitz President, Operations | May 15, 2026 | Tax Withhold | 11,204 | $12.82 | $143.6K | 496.8K | Form 4 ↗ |
Day David CHIEF FINANCIAL OFFICER | May 15, 2026 | Tax Withhold | 14,170 | $12.82 | $181.7K | 493.3K | Form 4 ↗ |
Saltz Aaron CHIEF LEGAL OFFICER | May 15, 2026 | Tax Withhold | 5,627 | $12.82 | $72.1K | 270.0K | Form 4 ↗ |
Gephart Brian CHIEF ACCOUNTING OFFICER | May 15, 2026 | Tax Withhold | 3,789 | $12.82 | $48.6K | 118.6K | Form 4 ↗ |
Buonasera David CHIEF TECHNOLOGY OFFICER | May 15, 2026 | Tax Withhold | 8,335 | $12.82 | $106.9K | 294.2K | Form 4 ↗ |
Soroca Adam Lee CHIEF PRODUCT OFFICER | Feb 15, 2026 | Tax Withhold | 18,933 | $11.70 | $221.5K | 410.0K | Form 4 ↗ |
Soroca Adam Lee CHIEF PRODUCT OFFICER | Feb 18, 2026 | Sale | 21,529 | $12.00 | $258.3K | 388.4K | Form 4 ↗ |
Source: /insider-trading/search (FMP stable). Buy/Sell direction: acquisitionOrDisposition A=Buy, D=Sell. RSU vesting (M-Exempt) excluded from sentiment bar. All data from SEC EDGAR public filings.
About institutional & insider ownership
Magnite, Inc. (MGNI) is primarily owned by institutional investors, who hold approximately 92.8% of total shares outstanding. Company insiders own approximately 1.46%, while retail and public investors account for the remaining 5.74%.
The largest institutional shareholder of Magnite, Inc. is VANGUARD GROUP INC, holding approximately 13.74 million shares — equal to 9.69% of outstanding shares — as of March 31, 2025.
A total of 318 institutional investors currently hold MGNI stock, with a combined institutional value of approximately $1.52 billion as of the most recent 13F filing period.
Frequently asked questions
MGNI ownershipMagnite, Inc. (MGNI) is primarily owned by institutional investors, who hold approximately 92.8% of shares. The largest shareholder is VANGUARD GROUP INC with a 9.69% stake. Company insiders hold 1.46%. Data sourced from SEC Form 13F as of March 31, 2025.