SEC ownership of MediaAlpha, Inc.

Top holders, 13D/G large-stake signals, insider positions, and transaction flow tied to CIK 0001818383.

Comparable stake leader

WHITE MOUNTAINS INSURANCE GROUP LTD

Disclosed value leader

WHITE MOUNTAINS INSURANCE GROUP LTD

Comparable rows

50/50

Latest evidence

25 Aug 2026

Top shareholders Insider holders Latest transactions
Public ticker
MAX on NYSE
Parsed ownership sources
3/4/5, 13D/G, and 13F
Source: Parsed SEC ownership filingsUse: Compare filing families carefully
Largest SEC-reported holder
WHITE MOUNTAINS INSURANCE GROUP LTD
Ranking: Comparable ownership first, then disclosed value
Ownership snapshot CIK-linked ownership evidence from parsed SEC filings. 3 signals
Comparable ownership rows
50 of 50
Meaning: Rows with safely comparable ownership %
Latest 13D/G holder
WHITE MOUNTAINS INSURANCE GROUP LTD
Source: Latest parsed Schedule 13D/G stake
Latest parsed ownership date
25 Aug 2026
Freshness: Most recent filing date in this holder set
Issuer Names, identifiers, and filing context for this profile. 2 identity fields
Issuer CIK
0001818383
Issuer location
Los Angeles, CA

Ownership snapshot

Top shareholders of MediaAlpha, 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
WHITE MOUNTAINS INSURANCE...
Disclosed value leader
WHITE MOUNTAINS INSURANCE...
Comparable rows
50/50
Latest evidence
25 Aug 2026
3/4/5 13D/G 13F Lead comparable stake: 33% 13D/G row: WHITE MOUNTAINS INSURANCE GROUP LTD Showing 1-8 of 50 holder rows.

Quick read

WHITE MOUNTAINS INSURANCE GROUP LTD leads the comparable SEC ownership view at 33%.

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 WHITE MOUNTAINS INSURANCE GROUP LTD's linked filing trail.
Comparable ownership Top 5
WHITE MOUNTAINS INSURANCE GROUP LTD 33%
Eugene Nonko 9.8%
Divisadero Street Capital Managem... 5.8%
VANGUARD GROUP INC 4.6%
BlackRock, Inc. 4.2%

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
WHITE MOUNTAINS INSURANCE GROUP LTD
3/4/5 13D/G 13F
10%+ Owner · Company
3/4/5 13D/G 13F
33%
from 13D/G
$339,275,666
17,856,614 shares
 — 07 May 2024
Eugene Nonko
13D/G 3/4/5
Director
13D/G 3/4/5
9.8%
$73,761,337
5,198,121 shares
 -$11,334,163 25 Aug 2026
Divisadero Street Capital Management, LP
13D/G 13F
Company
13D/G 13F
5.8%
$39,331,379
3,128,988 shares
 $0 21 Jul 2026
VANGUARD GROUP INC
13D/G
The Vanguard Group
13D/G
4.6%
$29,595,067
2,600,621 shares
 -$3,558,606 30 Sep 2025
BlackRock, Inc.
13F 13D/G
Company
13F 13D/G
4.2%
from 13D/G
$42,641,927
3,392,357 shares
 — 30 Jun 2026
VRABECK KATHY P
3/4/5
Director
3/4/5
0.28%
$1,398,785
150,407 shares
 — 05 May 2026
Venmal (raji) Arasu
3/4/5
Director
3/4/5
0.23%
$1,110,485
119,407 shares
 — 05 May 2026
Lara Sweet
3/4/5
Director
3/4/5
0.19%
$829,705
98,657 shares
 — 14 May 2025
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: -$31,991,372.

Buys
$0
Insiders: 0
Sells
$31,991,372
Insiders: 5
Net
-$31,991,372
Shares: -2,716,175
Window
Last 12 months
4 rolling buckets
Buy value Sell value
Shares: 0 Shares: 2,716,175
Window (months) Buy shares Sell shares Buy value Sell value Net value
0-3 0 1,068,072 $0 $14,192,530 -$14,192,530
3-6 0 546,114 $0 $5,375,409 -$5,375,409
6-9 0 710,189 $0 $7,458,372 -$7,458,372
9-12 0 391,800 $0 $4,965,061 -$4,965,061

Reporting owners

Insider holders from Forms 3/4/5

Showing 1-20 of 26 reporting-owner rows connected to MediaAlpha, Inc.. Open a relationship link for the CIK-to-CIK filing trail.

Rows
26
Largest Forms 3/4/5 holder
WHITE MOUNTAINS INSURANCE GROUP LTD
Net 12M change
-$31,991,373
Latest report
25 Sep 2026
Name Relationship Holdings Value Past Year Net Change Change % Valuation Report Date
WHITE MOUNTAINS INSURANCE GROUP LTD 10%+ Owner $339,275,666 Filing P/S 07 May 2024
WM Birkdale, Ltd. 10%+ Owner $153,342,381 Mixed 22 Dec 2022
INSIGNIA CAPITAL PARTNERS GP, L.L.C. 10%+ Owner $61,462,986 Mixed 09 May 2024
WM Hinson (Bermuda) Ltd. 10%+ Owner $56,564,761 Mixed 30 Jun 2023
Steven Yi CHIEF EXECUTIVE OFFICER, PRESIDENT, AND CO-FOUNDER, Director $29,907,241 -$13,562,972 -31% Mixed 01 Sep 2026
Eugene Nonko Director $18,753,949 -$16,028,637 -46% Mixed 21 Sep 2026
Patrick Ryan Thompson Chief Financial Officer and Treasurer $13,951,854 Mixed 15 Aug 2026
Jeffrey B. Coyne General Counsel And Secretary $7,583,990 -$142,789 -1.8% Mixed 15 Aug 2026
Kuanling Amy Yeh Chief Technology Officer $5,133,255 -$1,019,947 -17% Filing P/S 25 Sep 2026
Keith Cramer Chief Revenue Officer $3,574,289 -$1,237,028 -26% Mixed 15 Sep 2026
Ambrose Wang Co Founder $2,478,768 Mixed 30 Jul 2021
Brian Mikalis Senior Vice President, Demand Partnerships $2,139,216 Mixed 30 Oct 2021
Jeff Sweetser Vice President, Supply Partnerships $1,765,299 Mixed 30 Oct 2021
VRABECK KATHY P Director $1,398,785 Mixed 05 May 2026
Robert Perine Vice President, Product $1,317,798 Mixed 30 Oct 2021
Serge Topjian Vice President, Media $1,139,054 Mixed 30 Oct 2021
Venmal (raji) Arasu Director $1,110,485 Mixed 05 May 2026
Lara Sweet Director $829,705 Mixed 14 May 2025
Cort Allan Carlson VP, Corporate Controller and Interim Principal Financial and Accounting Officer $530,346 Mixed 15 Nov 2021
Bradley William Hunt Director $429,660 Mixed 05 May 2026

Recent insider transactions for MediaAlpha, 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
Kuanling Amy Yeh MAX Class A Common Stock Sale -0.55% $28,200 $9.40 -3,000 546,091 25 Sep 2026 Direct
Eugene Nonko MAX Class A Common Stock Sale -0.77% $71,854 $10.78 -6,667 854,550 22 Sep 2026 By O.N.E. Holdings,LLC
Eugene Nonko MAX Class A Common Stock Sale -0.13% $11,510 $10.79 -1,067 800,821 22 Sep 2026 Direct
Eugene Nonko MAX Class A Common Stock Sale -0.77% $70,216 $10.53 -6,667 861,217 21 Sep 2026 By O.N.E. Holdings,LLC
Eugene Nonko MAX Class A Common Stock Sale -0.13% $11,242 $10.54 -1,067 801,888 21 Sep 2026 Direct
Eugene Nonko MAX Class A Common Stock Sale -0.83% $81,733 $11.24 -7,273 867,884 16 Sep 2026 By O.N.E. Holdings,LLC
Eugene Nonko MAX Class A Common Stock Sale -0.24% $21,827 $11.25 -1,940 802,955 16 Sep 2026 Direct
Keith Cramer MAX Class A Common Stock Sale -4.92% $149,422 $11.49 -13,000 251,303 15 Sep 2026 Direct
Eugene Nonko MAX Class A Common Stock Sale -0.82% $83,538 $11.49 -7,273 875,157 15 Sep 2026 By O.N.E. Holdings,LLC
Eugene Nonko MAX Class A Common Stock Sale -0.24% $22,272 $11.48 -1,940 804,895 15 Sep 2026 Direct
Eugene Nonko MAX Class A Common Stock Sale -0.87% $93,005 $11.96 -7,778 882,430 14 Sep 2026 By O.N.E. Holdings,LLC
Eugene Nonko MAX Class A Common Stock Sale -0.33% $32,095 $12.03 -2,667 806,835 14 Sep 2026 Direct
Eugene Nonko MAX Class A Common Stock Sale -0.81% $84,506 $11.62 -7,273 890,208 10 Sep 2026 By O.N.E. Holdings,LLC
Eugene Nonko MAX Class A Common Stock Sale -0.24% $22,345 $11.52 -1,940 809,502 10 Sep 2026 Direct
Eugene Nonko MAX Class A Common Stock Sale -0.8% $82,954 $11.41 -7,273 897,481 09 Sep 2026 By O.N.E. Holdings,LLC
Eugene Nonko MAX Class A Common Stock Sale -0.24% $22,602 $11.65 -1,940 811,442 09 Sep 2026 Direct
Eugene Nonko MAX Class A Common Stock Sale -0.8% $85,106 $11.70 -7,273 904,754 08 Sep 2026 By O.N.E. Holdings,LLC
Eugene Nonko MAX Class A Common Stock Sale -0.24% $22,697 $11.70 -1,940 813,382 08 Sep 2026 Direct
Kuanling Amy Yeh MAX Class A Common Stock Sale -0.54% $36,000 $12.00 -3,000 549,091 04 Sep 2026 Direct
Eugene Nonko MAX Class A Common Stock Sale -0.85% $95,242 $12.24 -7,778 912,027 02 Sep 2026 By O.N.E. Holdings,LLC
Eugene Nonko MAX Class A Common Stock Sale -0.33% $32,581 $12.22 -2,667 815,322 02 Sep 2026 Direct
Steven Yi MAX Class A Common Stock Sale -2.01% $594,365 $12.38 -48,000 2,339,740 01 Sep 2026 Direct
Eugene Nonko MAX Class A Common Stock Sale -0.84% $96,394 $12.39 -7,778 919,805 01 Sep 2026 By O.N.E. Holdings,LLC
Eugene Nonko MAX Class A Common Stock Sale -0.32% $33,216 $12.45 -2,667 817,989 01 Sep 2026 Direct
Eugene Nonko MAX Class A Common Stock Sale -0.83% $98,061 $12.61 -7,778 927,583 31 Aug 2026 By O.N.E. Holdings,LLC
Eugene Nonko MAX Class A Common Stock Sale -0.32% $33,566 $12.59 -2,667 820,656 31 Aug 2026 Direct
Eugene Nonko MAX Class A Common Stock Sale -0.82% $97,641 $12.55 -7,778 935,361 26 Aug 2026 By O.N.E. Holdings,LLC
Eugene Nonko MAX Class A Common Stock Sale -0.32% $33,487 $12.56 -2,667 823,323 26 Aug 2026 Direct
Eugene Nonko MAX Class A Common Stock Sale -0.86% $105,574 $12.87 -8,205 943,139 25 Aug 2026 By O.N.E. Holdings,LLC
Eugene Nonko MAX Class A Common Stock Sale -0.4% $42,316 $12.89 -3,282 825,990 25 Aug 2026 Direct
Eugene Nonko MAX Class A Common Stock Sale -0.86% $106,564 $12.99 -8,205 951,344 24 Aug 2026 By O.N.E. Holdings,LLC
Eugene Nonko MAX Class A Common Stock Sale -0.39% $42,645 $12.99 -3,282 829,272 24 Aug 2026 Direct
Eugene Nonko MAX Class A Common Stock Sale -0.85% $108,523 $13.23 -8,205 959,549 19 Aug 2026 By O.N.E. Holdings,LLC
Eugene Nonko MAX Class A Common Stock Sale -0.39% $43,321 $13.20 -3,282 832,554 19 Aug 2026 Direct
Eugene Nonko MAX Class A Common Stock Sale -0.84% $105,704 $12.88 -8,205 967,754 18 Aug 2026 By O.N.E. Holdings,LLC
Eugene Nonko MAX Class A Common Stock Sale -0.39% $42,345 $12.90 -3,282 835,836 18 Aug 2026 Direct
Eugene Nonko MAX Class A Common Stock Sale -0.83% $104,858 $12.78 -8,205 975,959 17 Aug 2026 By O.N.E. Holdings,LLC
Eugene Nonko MAX Class A Common Stock Sale -0.39% $42,077 $12.82 -3,282 839,118 17 Aug 2026 Direct
Keith Cramer MAX Class A Common Stock Sale -4.69% $165,924 $12.76 -13,000 264,303 17 Aug 2026 Direct
Jeffrey B. Coyne MAX Class A Common Stock Tax liability -2.4% -14,182 577,582 15 Aug 2026 Direct
Patrick Ryan Thompson MAX Class A Common Stock Tax liability -2.19% -24,209 1,080,127 15 Aug 2026 Direct
Keith Cramer MAX Class A Common Stock Options Exercise 3.65% 9,775 277,303 15 Aug 2026 Direct
Keith Cramer MAX Restricted Stock Units Options Exercise -48% -9,775 10,607 15 Aug 2026 Direct
Kuanling Amy Yeh MAX Class A Common Stock Options Exercise 1.86% 10,106 552,091 15 Aug 2026 Direct
Kuanling Amy Yeh MAX Restricted Stock Units Options Exercise -48.8% -10,106 10,607 15 Aug 2026 Direct
Kuanling Amy Yeh MAX Class A Common Stock Sale -2.17% $162,617 $13.55 -12,000 541,985 14 Aug 2026 Direct
Eugene Nonko MAX Class A Common Stock Sale -0.83% $104,866 $12.78 -8,205 984,164 12 Aug 2026 By O.N.E. Holdings,LLC
Eugene Nonko MAX Class A Common Stock Sale -0.39% $42,289 $12.89 -3,282 842,400 12 Aug 2026 Direct
Eugene Nonko MAX Class A Common Stock Sale -0.82% $108,610 $13.24 -8,205 992,369 11 Aug 2026 By O.N.E. Holdings,LLC
Eugene Nonko MAX Class A Common Stock Sale -0.39% $43,835 $13.36 -3,282 845,682 11 Aug 2026 Direct
* marks a reported price that did not pass the local price check.
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