Comparable stake leader
VANGUARD PORTFOLIO MANAGEMENT LLC
SEC ownership of MAGNITE, INC.
Top holders, 13D/G large-stake signals, insider positions, and transaction flow tied to CIK 0001595974.
Disclosed value leader
BlackRock, Inc.
Comparable rows
50/50
Latest evidence
17 Sep 2026
- Public ticker
- MGNI on Nasdaq
- Parsed ownership sources
-
13F, 13D/G, and 3/4/5
Source: Parsed SEC ownership filingsUse: Compare filing families carefully
- Largest SEC-reported holder
-
VANGUARD PORTFOLIO MANAGEMENT LLC
Ranking: Comparable ownership first, then disclosed value
- Comparable ownership rows
-
50 of 50
Meaning: Rows with safely comparable ownership %
- Latest 13D/G holder
-
VANGUARD PORTFOLIO MANAGEMENT LLC
Source: Latest parsed Schedule 13D/G stake
- Latest parsed ownership date
-
17 Sep 2026
Freshness: Most recent filing date in this holder set
- Issuer CIK
- 0001595974
- Issuer location
- New York, NY
Ownership snapshot
CIK-linked ownership evidence from parsed SEC filings.
3 signals
Issuer
Names, identifiers, and filing context for this profile.
2 identity fields
Ownership snapshot
Top shareholders of MAGNITE, INC. (13F + 13D/G + 3/4/5)
Grouped by holder across the latest SEC ownership disclosures. Start with comparable ownership when available, then verify the linked 13F, 13D/G, or 3/4/5 evidence.
Comparable stake leader
VANGUARD PORTFOLIO MANAGE...
Disclosed value leader
BlackRock, Inc.
Comparable rows
50/50
Latest evidence
17 Sep 2026
13F
13D/G
3/4/5
Lead comparable stake: 5.4%
13D/G row: VANGUARD PORTFOLIO MANAGEMENT LLC
Showing 1-8 of 50 holder rows.
Quick read
VANGUARD PORTFOLIO MANAGEMENT LLC leads the comparable SEC ownership view at 5.4%.
50 of 50 rows have a safely comparable ownership percentage. Use this as a filing-backed starting point, then open the detailed table for source links, reporting role, position value, share count, and filing date.
Open SEC evidence
Opens VANGUARD PORTFOLIO MANAGEMENT LLC's linked filing trail.
Comparable ownership
Top 5
VANGUARD PORTFOLIO MANAGEMENT LLC
5.4%
FMR LLC
5.4%
VANGUARD CAPITAL MANAGEMENT LLC
5%
WELLINGTON MANAGEMENT GROUP LLP
4.2%
Capital Research Global Investors
3.5%
Ownership % is shown only when SEC disclosures are safely comparable across share classes.
Detailed SEC evidence table Showing 1-8 of 50 holder rows
| Holder | Evidence | Ownership % | Position | 12M Net Δ | As of |
|---|---|---|---|---|---|
| VANGUARD PORTFOLIO MANAGEMENT LLC |
13F
13D/G
Company · Vanguard Portfolio Management
|
5.4%
from 13D/G
|
$155,584,488
8,197,286 shares
|
— | 30 Jun 2026 |
| FMR LLC |
13D/G
13F
Company
|
5.4%
|
$157,593,938
7,759,426 shares
|
+$66,048,262 | 30 Jun 2026 |
| VANGUARD CAPITAL MANAGEMENT LLC |
13F
13D/G
Company · Vanguard Capital Management
|
5%
from 13D/G
|
$118,154,201
6,225,195 shares
|
— | 30 Jun 2026 |
| WELLINGTON MANAGEMENT GROUP LLP |
13D/G
13F
Company
|
4.2%
|
$122,763,633
6,044,492 shares
|
-$52,496,191 | 30 Jun 2026 |
| Capital Research Global Investors |
13F
13D/G
Company
|
3.5%
from 13D/G
|
$73,436,638
3,869,159 shares
|
— | 30 Jun 2026 |
| Katie Seitz Evans |
3/4/5
President, Product & Operations
|
0.31%
|
$11,309,822
441,800 shares
mixed-class rows
|
-$1,839,229 | 11 Sep 2026 |
| David Buonasera |
3/4/5
CHIEF TECHNOLOGY OFFICER
|
0.17%
|
$6,297,942
245,155 shares
mixed-class rows
|
-$840,594 | 14 Sep 2026 |
| Rachel Lam |
3/4/5
Director
|
0.16%
|
$5,571,779
230,620 shares
|
-$241,600 | 10 Aug 2026 |
How to read this table
Rows are grouped by holder and ranked first by SEC-reported ownership % when it is safely comparable, then by disclosed holdings value. — indicates unavailable or non-comparable values; "mixed-class rows" means the latest filing spans non-comparable classes.
Forms 3/4/5 flow
Insider trading overview
Net insider flow leans to selling over the last 12 months. Net value: -$27,047,356.
Buys
$0
Insiders: 0
Sells
$27,047,356
Insiders: 13
Net
-$27,047,356
Shares: -1,305,727
Window
Last 12 months
4 rolling buckets
Buy value
Sell value
Shares: 0
Shares: 1,305,727
| Window (months) | Buy shares | Sell shares | Buy value | Sell value | Net value |
|---|---|---|---|---|---|
| 0-3 | 0 | 834,718 | $0 | $19,103,618 | -$19,103,618 |
| 3-6 | 0 | 381,806 | $0 | $6,493,340 | -$6,493,340 |
| 6-9 | 0 | 21,529 | $0 | $258,348 | -$258,348 |
| 9-12 | 0 | 67,674 | $0 | $1,192,049 | -$1,192,049 |
Reporting owners
Insider holders from Forms 3/4/5
Showing 1-20 of 22 reporting-owner rows connected to MAGNITE, INC.. Open a relationship link for the CIK-to-CIK filing trail.
Rows
22
Largest Forms 3/4/5 holder
Katie Seitz Evans
Net 12M change
-$26,651,068
Latest report
17 Sep 2026
| Name | Relationship | Holdings Value | Past Year Net Change | Change % | Valuation | Report Date |
|---|---|---|---|---|---|---|
| Katie Seitz Evans | President, Product & Operations | $11,309,822 | -$1,839,229 | -14% | Mixed | 11 Sep 2026 |
| David Day | Chief Financial Officer | $9,326,301 | Mixed | 15 Aug 2026 | ||
| Sean Patrick Buckley | President, Revenue & Market Strategy | $8,033,122 | -$2,776,476 | -26% | Mixed | 15 Aug 2026 |
| Michael G. Barrett | CEO, Director | $7,452,876 | -$13,639,789 | -65% | Median | 15 Aug 2026 |
| David Buonasera | Chief Technology Officer | $6,297,942 | -$840,594 | -12% | Mixed | 14 Sep 2026 |
| Rachel Lam | Director | $5,571,779 | -$241,600 | -4.2% | Filing P/S | 10 Aug 2026 |
| Aaron Saltz | Chief Legal Officer | $5,545,329 | -$936,400 | -14% | Mixed | 10 Sep 2026 |
| Adam Lee Soroca | Chief Product Officer | $5,087,511 | -$685,138 | -12% | Mixed | 15 Feb 2026 |
| Thomas Kershaw | Chief Technology Officer | $3,737,990 | Mixed | 17 May 2021 | ||
| Paul Caine | Director | $3,641,126 | -$828,850 | -19% | Filing P/S | 17 Sep 2026 |
| Sarah Patricia Harden | Director | $2,754,024 | -$1,154,585 | -30% | Filing P/S | 26 Aug 2026 |
| Joseph R. Prusz | Chief Revenue Officer, DV+ | $2,454,445 | Mixed | 15 Feb 2022 | ||
| Brian Gephart | Chief Accounting Officer | $1,942,185 | -$307,982 | -14% | Median | 15 Aug 2026 |
| James Allen Dove | Chief Technology Officer | $1,507,550 | Mixed | 15 Aug 2022 | ||
| Shawna Hughes | Chief Accounting Officer | $1,405,438 | Mixed | 17 May 2021 | ||
| Robert F. Spillane | Director | $1,371,308 | -$557,275 | -29% | Filing P/S | 14 Sep 2026 |
| Douglas S. Knopper | Director | $1,343,854 | -$2,674,662 | -67% | Filing P/S | 17 Sep 2026 |
| James Rossman | Director | $1,276,826 | Mixed | 08 Jun 2026 | ||
| Pearson David T. | Director | $1,236,365 | -$168,488 | -12% | Filing P/S | 08 Jun 2026 |
| Diane Yu | Director | $965,594 | Mixed | 08 Jun 2026 |
Recent insider transactions for MAGNITE, INC.
Showing up to 300 recent insider transactions from the last 12 months.
| Insider | Symbol | Class | Transaction | % | SEC-reported value | SEC-reported price | Shares | Shares owned | Date | Ownership |
|---|---|---|---|---|---|---|---|---|---|---|
| Paul Caine | MGNI | Common Stock | Sale | -5.18% | $198,750 | $26.50 | -7,500 | 137,401 | 17 Sep 2026 | Direct |
| Douglas S. Knopper | MGNI | Common Stock | Sale | -42.2% | $981,216 | $26.28 | -37,337 | 51,136 | 17 Sep 2026 | Direct |
| David Buonasera | MGNI | Common Stock | Sale | -0.47% | $27,960 | $24.00 | -1,165 | 245,155 | 14 Sep 2026 | Direct |
| Robert F. Spillane | MGNI | Common Stock | Sale | -15.2% | $246,225 | $23.76 | -10,363 | 57,715 | 14 Sep 2026 | Direct |
| Robert F. Spillane | MGNI | Common Stock | Options Exercise | 18% | 10,363 | 68,078 | 14 Sep 2026 | Direct | ||
| Robert F. Spillane | MGNI | Stock Option (right to buy) | Options Exercise | -100% | -10,363 | 0 | 14 Sep 2026 | Direct | ||
| Katie Seitz Evans | MGNI | Common Stock | Sale | -3.07% | $335,928 | $24.00 | -13,997 | 441,800 | 11 Sep 2026 | Direct |
| Aaron Saltz | MGNI | Common Stock | Sale | -15.1% | $936,400 | $23.41 | -40,000 | 224,389 | 10 Sep 2026 | Direct |
| Paul Caine | MGNI | Common Stock | Sale | -3.34% | $117,650 | $23.53 | -5,000 | 144,901 | 10 Sep 2026 | Direct |
| Katie Seitz Evans | MGNI | Common Stock | Sale | -2.38% | $260,406 | $23.46 | -11,100 | 455,797 | 09 Sep 2026 | Direct |
| Katie Seitz Evans | MGNI | Common Stock | Sale | -6.47% | $762,895 | $23.63 | -32,285 | 466,897 | 08 Sep 2026 | Direct |
| Katie Seitz Evans | MGNI | Common Stock | Options Exercise | 2.79% | 13,546 | 499,182 | 08 Sep 2026 | Direct | ||
| Katie Seitz Evans | MGNI | Employee Stock Option (Right to Buy) | Options Exercise | -100% | -13,546 | 0 | 08 Sep 2026 | Direct | ||
| David Buonasera | MGNI | Common Stock | Sale | -0.42% | $26,075 | $25.00 | -1,043 | 246,320 | 02 Sep 2026 | Direct |
| David Buonasera | MGNI | Common Stock | Sale | -2.13% | $125,789 | $23.42 | -5,371 | 247,363 | 01 Sep 2026 | Direct |
| Sarah Patricia Harden | MGNI | Common Stock | Sale | -13.8% | $442,464 | $24.00 | -18,436 | 114,751 | 28 Aug 2026 | Direct |
| Sarah Patricia Harden | MGNI | Common Stock | Sale | -18.7% | $712,120 | $23.31 | -30,550 | 133,187 | 26 Aug 2026 | Direct |
| Sean Patrick Buckley | MGNI | Common Stock | Sale | -0.93% | $68,975 | $25.00 | -2,759 | 293,060 | 18 Aug 2026 | Direct |
| Sean Patrick Buckley | MGNI | Common Stock | Sale | -2.72% | $201,068 | $24.31 | -8,271 | 295,819 | 17 Aug 2026 | Direct |
| David Buonasera | MGNI | Common Stock | Tax liability | -3.11% | -8,102 | 252,734 | 15 Aug 2026 | Direct | ||
| Katie Seitz Evans | MGNI | Common Stock | Tax liability | -2.26% | -11,204 | 485,636 | 15 Aug 2026 | Direct | ||
| Aaron Saltz | MGNI | Common Stock | Tax liability | -2.08% | -5,627 | 264,389 | 15 Aug 2026 | Direct | ||
| Brian Gephart | MGNI | Common Stock | Tax liability | -3.57% | -3,789 | 102,328 | 15 Aug 2026 | Direct | ||
| Michael G. Barrett | MGNI | Common Stock | Tax liability | -2.58% | -10,404 | 392,670 | 15 Aug 2026 | Direct | ||
| David Day | MGNI | Common Stock | Tax liability | -3.03% | -14,170 | 452,861 | 15 Aug 2026 | Direct | ||
| Sean Patrick Buckley | MGNI | Common Stock | Tax liability | -3.71% | -11,715 | 304,090 | 15 Aug 2026 | Direct | ||
| Paul Caine | MGNI | Common Stock | Sale | -4.76% | $187,500 | $25.00 | -7,500 | 149,901 | 14 Aug 2026 | Direct |
| David Day | MGNI | Common Stock | Gift | -5.32% | -26,258 | 467,031 | 13 Aug 2026 | Direct | ||
| Brian Gephart | MGNI | Common Stock | Sale | -10.5% | $307,982 | $24.68 | -12,479 | 106,117 | 10 Aug 2026 | Direct |
| Rachel Lam | MGNI | Common Stock | Sale | -4.16% | $241,600 | $24.16 | -10,000 | 230,620 | 10 Aug 2026 | Direct |
| Paul Caine | MGNI | Common Stock | Sale | -3.08% | $121,750 | $24.35 | -5,000 | 157,401 | 10 Aug 2026 | Direct |
| Sean Patrick Buckley | MGNI | Common Stock | Sale | -17.5% | $1,645,316 | $24.49 | -67,179 | 315,805 | 06 Aug 2026 | Direct |
| Sean Patrick Buckley | MGNI | Common Stock | Options Exercise | 8.1% | 28,703 | 382,984 | 06 Aug 2026 | Direct | ||
| Sean Patrick Buckley | MGNI | Stock Option (right to buy) | Options Exercise | -33.3% | -28,703 | 57,405 | 06 Aug 2026 | Direct | ||
| Douglas S. Knopper | MGNI | Common Stock | Sale | -29.7% | $848,297 | $22.72 | -37,337 | 88,473 | 06 Aug 2026 | Direct |
| David Buonasera | MGNI | Common Stock | Sale | -2.85% | $179,478 | $23.46 | -7,649 | 260,836 | 06 Aug 2026 | Direct |
| Katie Seitz Evans | MGNI | Common Stock | Sale | -3.87% | $480,000 | $24.00 | -20,000 | 496,840 | 06 Aug 2026 | Direct |
| Katie Seitz Evans | MGNI | Common Stock | Options Exercise | 4.03% | 20,000 | 516,840 | 06 Aug 2026 | Direct | ||
| Katie Seitz Evans | MGNI | Employee Stock Option (Right to Buy) | Options Exercise | -100% | -20,000 | 0 | 06 Aug 2026 | Direct | ||
| Michael G. Barrett | MGNI | Common Stock | Sale | -42.2% | $6,678,953 | $22.72 | -293,968 | 403,074 | 06 Aug 2026 | Direct |
| Michael G. Barrett | MGNI | Common Stock | Options Exercise | 72.9% | 293,968 | 697,042 | 06 Aug 2026 | Direct | ||
| Michael G. Barrett | MGNI | Stock Option (right to buy) | Options Exercise | -100% | -293,968 | 0 | 06 Aug 2026 | Direct | ||
| Michael G. Barrett | MGNI | Common Stock | Sale | -8.74% | $785,429 | $20.35 | -38,596 | 403,074 | 15 Jul 2026 | Direct |
| Michael G. Barrett | MGNI | Common Stock | Options Exercise | 9.58% | 38,596 | 441,670 | 15 Jul 2026 | Direct | ||
| Michael G. Barrett | MGNI | Employee Stock Option (Right to Buy) | Options Exercise | -11.6% | -38,596 | 293,968 | 15 Jul 2026 | Direct | ||
| Paul Caine | MGNI | Common Stock | Sale | -2.99% | $103,200 | $20.64 | -5,000 | 162,401 | 10 Jul 2026 | Direct |
| David Buonasera | MGNI | Common Stock | Sale | -0.45% | $25,704 | $21.00 | -1,224 | 268,485 | 07 Jul 2026 | Direct |
| Sean Patrick Buckley | MGNI | Common Stock | Sale | -5.15% | $404,470 | $21.03 | -19,233 | 354,281 | 07 Jul 2026 | Direct |
| David Buonasera | MGNI | Common Stock | Sale | -3.36% | $187,520 | $20.00 | -9,376 | 269,709 | 01 Jul 2026 | Direct |
| Michael G. Barrett | MGNI | Common Stock | Sale | -15.7% | $1,462,500 | $19.50 | -75,000 | 403,074 | 29 Jun 2026 | Direct |
* marks a reported price that did not pass the local price check.