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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 Mar 2026
the date the book describes
Filed
18 May 2026
latest of these filings; the earliest 12 May 2026
Managers listing it
27
at least, of 95 tracked, among listed positions
Comparable managers
91
filed both Q4 2025 and Q1 2026; 4 listed it in both
Shares listed
29,756,464
combined, among listed positions
Reported value
$354m
combined, at the quarter end

AllianceBernstein LP. Values in this filing are at the previous quarter end's prices; its share count is the quarter end's.

Among the 91 comparable managers: 22 buyers (opened or added shares) and 7 sellers (trimmed or exited), at least, among listed positions. Their net change in shares was -4,040,500.

Managers listing MGNI in Q1 2026

Share of 13F value is the position’s reported value over everything the manager reported that quarter. The share change is against Q4 2025, and only where both filings list the position. A rise in value with no rise in shares is the price, not buying.

27 of 27 holders

ActionFiling
Wellington Management Group LLP9,191,077$109munder 0.1%Added+561,83915 May 2026 (the filing on sec.gov)
Capital Research Global Investors5,020,289$60munder 0.1%Trimmed-7,900,00013 May 2026 (the filing on sec.gov)
Fidelity (FMR LLC)4,507,419$54munder 0.1%Trimmed-2,193,75515 May 2026 (the filing on sec.gov)
Jane Street Group LLC1,668,160$20munder 0.1%Added+1,287,90712 May 2026 (the filing on sec.gov)
Schonfeld Strategic Advisors LLC1,605,041$19m0.13%Added+825,36015 May 2026 (the filing on sec.gov)
Balyasny Asset Management LLC1,500,443$18munder 0.1%Added+627,23515 May 2026 (the filing on sec.gov)
Millennium Management LLC1,234,457$15munder 0.1%Added+1,210,71315 May 2026 (the filing on sec.gov)
Citadel Advisors LLC1,052,908$13munder 0.1%Added+508,59015 May 2026 (the filing on sec.gov)
Man Group PLC663,957$7.9munder 0.1%Added+352,42115 May 2026 (the filing on sec.gov)
Capital World Investors456,672$5.4munder 0.1%Newnew13 May 2026 (the filing on sec.gov)
First Eagle Investment Management LLC450,288$5.3munder 0.1%Added+153,84514 May 2026 (the filing on sec.gov)
Two Sigma Investments LP394,856$4.7munder 0.1%Added+31,44415 May 2026 (the filing on sec.gov)
Susquehanna International Group LLP307,805$3.7munder 0.1%Added+19815 May 2026 (the filing on sec.gov)
AllianceBernstein LP223,191$3.6munder 0.1%Added+97,84615 May 2026 (the filing on sec.gov)
Squarepoint Ops LLC300,934$3.6munder 0.1%Added+255,49615 May 2026 (the filing on sec.gov)
Invesco Ltd261,370$3.1munder 0.1%Added+17,80512 May 2026 (the filing on sec.gov)
T. Rowe Price Associates Inc165,440$2.0munder 0.1%Trimmed-546,05515 May 2026 (the filing on sec.gov)
ExodusPoint Capital Management LP149,219$1.8munder 0.1%Newnew14 May 2026 (the filing on sec.gov)
Brevan Howard Capital Management LP133,245$1.6munder 0.1%Newnew15 May 2026 (the filing on sec.gov)
AQR Capital Management LLC121,212$1.4munder 0.1%Added+23,67715 May 2026 (the filing on sec.gov)
Holocene Advisors LP101,973$1.2munder 0.1%Added+86,41115 May 2026 (the filing on sec.gov)
Tudor Investment Corp73,645$875kunder 0.1%Added+38,97115 May 2026 (the filing on sec.gov)
GAMCO Investors Inc60,653$721kunder 0.1%Added+16,17414 May 2026 (the filing on sec.gov)
Janus Henderson Group Ltd58,423$694kunder 0.1%Held018 May 2026 (the filing on sec.gov)
Marshall Wace LLP42,468$505kunder 0.1%Added+13,70515 May 2026 (the filing on sec.gov)
Page 1 of 2

Largest increases and reductions, by shares

Q4 2025 to Q1 2026, 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 (4)

Exited (3)

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 →