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MGNI in the 13F filings

Magnite Inc · CUSIP 55955D100

Sector · Software and IT servicesTheme · Internet, programming and data services
Quarter
Q2 2026Q1 2026Q4 2025Q3 2025Q2 2025Q1 2025Q4 2024Q3 2024Q2 2024Q3 2023Q2 2023Q1 2023
Quarter end
31 Dec 2025
the date the book describes
Filed
19 Feb 2026
latest of these filings; the earliest 4 Feb 2026
Managers listing it
26
at least, of 95 tracked, among listed positions
Comparable managers
92
filed both Q3 2025 and Q4 2025; 2 listed it in both
Shares listed
33,796,964
combined, among listed positions
Reported value
$549m
combined, at the quarter end

Among the 92 comparable managers: 12 buyers (opened or added shares) and 17 sellers (trimmed or exited), at least, among listed positions. Their net change in shares was -3,768,898.

Managers listing MGNI in Q4 2025

Share of 13F value is the position’s reported value over everything the manager reported that quarter. The share change is against Q3 2025, and only where both filings list the position. A rise in value with no rise in shares is the price, not buying.

26 of 26 holders

ActionFiling
Capital Research Global Investors12,920,289$210munder 0.1%Added+5,937,42811 Feb 2026 (the filing on sec.gov)
Wellington Management Group LLP8,629,238$140munder 0.1%Added+3,484,68917 Feb 2026 (the filing on sec.gov)
Fidelity (FMR LLC)6,701,174$109munder 0.1%Trimmed-10,439,84017 Feb 2026 (the filing on sec.gov)
Balyasny Asset Management LLC873,208$14munder 0.1%Newnew17 Feb 2026 (the filing on sec.gov)
Schonfeld Strategic Advisors LLC779,681$13m0.06%Newnew17 Feb 2026 (the filing on sec.gov)
T. Rowe Price Associates Inc711,495$12munder 0.1%Trimmed-1,836,01017 Feb 2026 (the filing on sec.gov)
Citadel Advisors LLC544,318$8.8munder 0.1%Added+374,75717 Feb 2026 (the filing on sec.gov)
Jane Street Group LLC380,253$6.2munder 0.1%Trimmed-710,37012 Feb 2026 (the filing on sec.gov)
Two Sigma Investments LP363,412$5.9munder 0.1%Added+62,98117 Feb 2026 (the filing on sec.gov)
Man Group PLC311,536$5.1munder 0.1%Newnew17 Feb 2026 (the filing on sec.gov)
Susquehanna International Group LLP307,607$5.0munder 0.1%Trimmed-305,37817 Feb 2026 (the filing on sec.gov)
First Eagle Investment Management LLC296,443$4.8munder 0.1%Trimmed-279,0004 Feb 2026 (the filing on sec.gov)
Invesco Ltd243,565$4.0munder 0.1%Trimmed-15,16719 Feb 2026 (the filing on sec.gov)
Bridgewater Associates LP145,187$2.4munder 0.1%Trimmed-48413 Feb 2026 (the filing on sec.gov)
AllianceBernstein LP125,345$2.0munder 0.1%Trimmed-19,30017 Feb 2026 (the filing on sec.gov)
AQR Capital Management LLC97,535$1.6munder 0.1%Added+49,46417 Feb 2026 (the filing on sec.gov)
Verition Fund Management LLC62,277$1.0munder 0.1%Trimmed-26,01913 Feb 2026 (the filing on sec.gov)
Janus Henderson Group Ltd58,423$948kunder 0.1%Held017 Feb 2026 (the filing on sec.gov)
Squarepoint Ops LLC45,438$737kunder 0.1%Trimmed-121,03113 Feb 2026 (the filing on sec.gov)
GAMCO Investors Inc44,479$722kunder 0.1%Trimmed-11,9905 Feb 2026 (the filing on sec.gov)
Tudor Investment Corp34,674$563kunder 0.1%Trimmed-414,43517 Feb 2026 (the filing on sec.gov)
Marshall Wace LLP28,763$467kunder 0.1%Added+16,11513 Feb 2026 (the filing on sec.gov)
Freestone Grove Partners LP27,761$451kunder 0.1%Newnew17 Feb 2026 (the filing on sec.gov)
Walleye Capital LLC25,557$415kunder 0.1%Newnew13 Feb 2026 (the filing on sec.gov)
Millennium Management LLC23,744$385kunder 0.1%Trimmed-652,60517 Feb 2026 (the filing on sec.gov)
Page 1 of 2

Largest increases and reductions, by shares

Q3 2025 to Q4 2025, among managers that listed it in both quarters or opened it.

Increases

Reductions

New positions and exits

At least these many: a manager is shown exiting only where its own filing shows the position gone.

New (6)

Exited (4)

Ownership over time

Every quarter on file. A quarter-end value moves with the price as well as with the shares held; buyers and sellers count comparable managers, by shares.
1 in Q3 2024 to 5 in Q2 2026

Tracked managers listing it, at least.

024620212022202320252026
the quarter shown share split complete books; unmarked quarters rest on listed positionsClick a quarter to open it.
MGNI by quarter
QuarterHoldersReported valueBuyersSellers
Q4 20201$5.7mn.a.n.a.
Q1 20212$94mn.a.n.a.
Q2 20215$88mn.a.n.a.
Q3 20213$43mn.a.n.a.
Q4 20214$38mn.a.n.a.
Q1 20221$1.2mn.a.n.a.
Q2 20222$1.9mn.a.n.a.
Q3 20223$5.4mn.a.n.a.
Q4 20221$4.2mn.a.n.a.
Q1 20232$3.1mn.a.n.a.
Q2 20232$6.6mn.a.n.a.
Q3 20231$1.7mn.a.n.a.
Q2 20241$21m10
Q3 20241$50m10
Q4 20242$129m20
Q1 20253$163m30
Q2 20256$520m32
Q3 20252$165m03
Q4 20254$367m1217
Q1 20263$84m227
Q2 20265$104m1316

Compare with…

Holders over time, buyers and sellers, and the managers holding both, side by side for up to four stocks.

MGNI and GOOGL →MGNI and META →MGNI and SPCX →Choose a stock to compare with MGNI →

How much of the picture this is

A 13F is a manager’s long US-listed equity book at a quarter end, filed up to 45 days later. It shows no shorts, cash, bonds or performance, and it is never today’s portfolio. Large books are listed to their largest positions, so a manager missing from this table may still hold a small position below that line. These are 95 tracked managers, not the institutional market.

Which funds own MGNI, latest filings →Back to the 13F Explorer →