As of November 7, 2026, 3 holders' latest Schedule 13D or 13G filings report owning 5% or more of MediaAlpha, Inc. The largest reported stake is White Mountains Insurance Group, Ltd.'s, at 24.3%. 8 filings are on record since August 8, 2025 (Schedule 13D/A, November 5, 2026).
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Key facts
- · Reporting person: White Mountains Insurance Group, Ltd. · Sole voting: 900,000 · Shared voting: 11,456,223 · Sole dispositive: 900,000 · Shared dispositive: 11,456,223 · SCHEDULE 13D/A, 2026-11-05
- · Holder: White Mountains Insurance Group, Ltd. · Percent: 35.1% · SCHEDULE 13D/A
- · Reporting person: Eugene Nonko · Sole voting: 5,198,121 · Shared voting: 0 · Sole dispositive: 5,198,121 · Shared dispositive: 0 · SCHEDULE 13D/A, 2026-08-26
- · Reporting person: Divisadero Street Capital Management, LP · Sole voting: 0 · Shared voting: 3,128,988 · Sole dispositive: 0 · Shared dispositive: 3,128,988 · SCHEDULE 13G, 2026-07-28
- · Holder: White Mountains Insurance Group, Ltd. · Percent: 33.03% · SCHEDULE 13D/A
MediaAlpha, Inc. has 8 Schedule 13D or 13G filings on record since 2025-08-08. 3 holders' latest filing reports 5% or more of class a common stock, par value $0.01 per share. Each figure below is the holder's own, as filed, with the filing linked.
Holders
| Holder | Percent | Shares | Latest | Event date |
|---|---|---|---|---|
| White Mountains Insurance Group, Ltd. | 24.3% | 12,356,223 | SCHEDULE 13D/A, 2026-11-05 | 2026-11-04 |
| 9.8% | 5,198,121 | SCHEDULE 13D/A, 2026-08-26 | 2026-08-25 | |
| Divisadero Street Capital Management, LP | 5.8% | 3,128,988 | SCHEDULE 13G, 2026-07-28 | 2026-07-21 |
| The Vanguard Group | 4.61% | 2,600,621 | SCHEDULE 13G/A, 2025-10-31 | 2025-09-30 |
| Insignia Capital Partners GP, L.L.C. | 0% | 0 | SCHEDULE 13G/A, 2025-11-12 | 2025-09-30 |
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More on MediaAlpha, Inc. and the records around it.
MediaAlpha, Inc. elsewhere on the record
- Leadership changes Sep 2026
- Who owns it
Companies that share a holder
- Divisadero Street Capital Management, LP also filed stake reports on 22 other companies: Rush Street Interactive, Inc. (Sep 2026), Build-a-Bear Workshop, Inc (Aug 2026), Citi Trends, Inc. (Aug 2026)
- The Vanguard Group also filed stake reports on 2384 other companies: BellRing Brands, Inc. (Sep 2026), CAL-MAINE FOODS INC (Sep 2026), FTAI Aviation Ltd. (Sep 2026)
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Voting and dispositive power, as filed
| Reporting person | Sole voting | Shared voting | Sole dispositive | Shared dispositive | Filing |
|---|---|---|---|---|---|
| White Mountains Insurance Group, Ltd. | 900,000 | 11,456,223 | 900,000 | 11,456,223 | SCHEDULE 13D/A, 2026-11-05 |
| WM Hinson (Bermuda) Ltd. | 0 | 11,456,223 | 0 | 11,456,223 | SCHEDULE 13D/A, 2026-11-05 |
| Eugene Nonko | 5,198,121 | 0 | 5,198,121 | 0 | SCHEDULE 13D/A, 2026-08-26 |
| O.N.E. Holdings, LLC | 4,905,412 | 0 | 4,905,412 | 0 | SCHEDULE 13D/A, 2026-08-26 |
| Divisadero Street Capital Management, LP | 0 | 3,128,988 | 0 | 3,128,988 | SCHEDULE 13G, 2026-07-28 |
| William Zolezzi | 0 | 3,128,988 | 0 | 3,128,988 | SCHEDULE 13G, 2026-07-28 |
| Divisadero Street Partners, L.P. | 0 | 2,993,988 | 0 | 2,993,988 | SCHEDULE 13G, 2026-07-28 |
| Divisadero Street Partners GP, LLC | 0 | 2,993,988 | 0 | 2,993,988 | SCHEDULE 13G, 2026-07-28 |
| Divisadero Street Capital, LLC | 0 | 3,128,988 | 0 | 3,128,988 | SCHEDULE 13G, 2026-07-28 |
The latest filing identifies MediaAlpha, Inc. by CUSIP 58450V104 and gives its principal executive office as 700 South Flower Street, Suite 640, Los Angeles, CA 90017 (SCHEDULE 13D/A, 2026-11-05).
Purpose of Transaction (Item 4)
White Mountains Insurance Group, Ltd.
Item 4 is amended and supplemented as follows: On November 4, 2026, WM Hinson sold 5,500,391 Class A Shares to J.P. Morgan Securities LLC pursuant to Rule 144 at a price of $13.90 per share (the "Sale"). Following the Sale, the Reporting Persons beneficially own approximately 24.27% of the Class A Shares, based on 50,903,805 Class A Shares outstanding as of October 26, 2026, as reported in the Issuer's Form 10-Q filed with the Commission on October 28, 2026 (such number of Class A Shares issued and outstanding, the "Class A Shares Outstanding"). The purpose of the Sale was to monetize a portion of the Reporting Persons' ownership interest in the Issuer.Item 4 of the SCHEDULE 13D/A filed 2026-11-05
Timeline
| Filed | Holder | Percent | Filing |
|---|---|---|---|
| 2025-08-08 | White Mountains Insurance Group, Ltd. | 31.7% | SCHEDULE 13D/A |
| 2025-10-31 | The Vanguard Group | 4.61% | SCHEDULE 13G/A |
| 2025-11-12 | Insignia Capital Partners GP, L.L.C. | 0% | SCHEDULE 13G/A |
| 2026-05-01 | White Mountains Insurance Group, Ltd. | 33.03% | SCHEDULE 13D/A |
| 2026-07-28 | Divisadero Street Capital Management, LP | 5.8% | SCHEDULE 13G |
| 2026-08-26 | Eugene Nonko | 9.8% | SCHEDULE 13D/A |
| 2026-10-30 | White Mountains Insurance Group, Ltd. | 35.1% | SCHEDULE 13D/A |
| 2026-11-05 | White Mountains Insurance Group, Ltd. | 24.3% | SCHEDULE 13D/A |
Questions about who owns MediaAlpha, Inc.
Who owns MediaAlpha, Inc.?
On this page, 3 holders' latest ownership filings report 5% or more of MediaAlpha, Inc.: White Mountains Insurance Group, Ltd. (24.3%, Schedule 13D/A, filed 2026-11-05), Eugene Nonko (9.8%, Schedule 13D/A, filed 2026-08-26) and Divisadero Street Capital Management, LP (5.8%, Schedule 13G, filed 2026-07-28).
Who are the largest shareholders of MediaAlpha, Inc.?
By the share each holder's latest filing reports, the largest holders of MediaAlpha, Inc. on this page are White Mountains Insurance Group, Ltd. (24.3%), Eugene Nonko (9.8%) and Divisadero Street Capital Management, LP (5.8%).
When did White Mountains Insurance Group, Ltd. buy into MediaAlpha, Inc.?
The filings give report dates, not purchase dates. The earliest filing from White Mountains Insurance Group, Ltd. on this page is the Schedule 13D/A, filed 2025-08-08, reporting 31.7%; its latest, Schedule 13D/A filed 2026-11-05, reports 24.3%. That earliest filing is itself an amendment, which updates an earlier report.
Is this an audit or a full list?
Neither. The ownership list on this page covers only Schedule 13D and 13G filings, which holders make once they own 5% or more of a class of shares (an amendment can report a stake that has since fallen below 5%); 8 such filings are shown here. It is not an audit and not a full cap table: holders who never reached 5% are not listed, and a stake can change after its latest filing.
Also on the record for MediaAlpha, Inc.
| Date | Record | Figure | Our page | Source |
|---|---|---|---|---|
| September 3, 2026 | Leadership change: Patrick Thompson departs, Chief Financial Officer | — | Leadership changes | Source |
| May 18, 2026 | Leadership change filing (Form 8-K, Item 5.02) | — | Leadership changes | Source |
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Where this comes from
Anyone who comes to own more than 5% of a class of a listed company's voting shares has to tell the SEC. A holder who may seek to change or influence the company files Schedule 13D, and has to say in Item 4, "Purpose of Transaction", what it intends to do. A holder with no such intent, such as many index and passive funds, may file the shorter Schedule 13G. Both are amended when the stake changes, including when it falls below 5%.
Every row here is one of those filings, linked to the filing itself. Percentages and share counts are exactly as the holder filed them, for the holder the filing names; an amendment showing a lower figure is shown as filed. Item 4 text is quoted word for word. Where a 13D's Item 4 contains a sentence stating a definite intent to influence the company, that sentence is marked and quoted; the page does not describe the holder or its motives beyond the words it filed. Nothing here is investment advice.