Capital Research reports 3.5% stake in Magnite

Magnite, Inc. ownership update: Capital Research Global Investors reports beneficial ownership of 5,020,289 shares, representing 3.5% of Magnite's common stock as of 03/31/2026.

Rhea-AI Filing Summary

Magnite, Inc. ownership update: Capital Research Global Investors reports beneficial ownership of 5,020,289 shares, representing 3.5% of Magnite's common stock as of 03/31/2026. The filer states sole voting and dispositive power over the same 5,020,289 shares. The amendment is signed by a Capital Research officer on 05/11/2026.

Insights

Institutional Ownership Analyst

Large institutional holder reports a 3.5% stake in Magnite.

Capital Research Global Investors is reported as the beneficial owner of 5,020,289 shares, with sole voting and dispositive power. The filing identifies the stake as 3.5% of the 144,364,365 shares believed outstanding as of 03/31/2026.

The filing is a standard beneficial-ownership amendment; cash-flow treatment and plans for these shares are not described in the excerpt. Subsequent filings would disclose any changes in the stake or voting arrangements.

Key Figures

Shares beneficially owned: 5,020,289 shares Percent of class: 3.5% Shares outstanding (believed): 144,364,365 shares +1 more

4 metrics

Shares beneficially owned 5,020,289 shares reported by Capital Research Global Investors

Percent of class 3.5% of common stock as reported in the filing

Shares outstanding (believed) 144,364,365 shares shares believed to be outstanding as of 03/31/2026

Sole voting power 5,020,289 shares sole voting power reported over the same shares

Key Terms

Schedule 13G/A, beneficially owned, sole dispositive power

3 terms

Schedule 13G/A regulatory

"Capital Research Global Investors reports beneficial ownership on Schedule 13G/A (Amendment No. 1)"

A Schedule 13G/A is an amended public filing with the U.S. securities regulator that updates a previous Schedule 13G, disclosing when an individual or group holds a substantial (typically over 5%) stake in a company and is claiming a passive, non‑controlling intent. Investors monitor these updates because rising or falling holdings can signal changing confidence, potential future moves, or shifts in voting power — like watching a public ledger where large shareholders quietly adjust their positions.

beneficially owned financial

"CRGI is deemed to be the beneficial owner of 5,020,289 shares"

Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.

sole dispositive power regulatory

"Sole Dispositive Power 5,020,289.00 in the ownership table"

Sole dispositive power is the exclusive legal authority to decide what happens to a security — for example, whether to sell, transfer, or retain shares — without needing anyone else’s permission. Investors care because it signals who truly controls the economic outcome of an investment: like holding the only key to a safe, the holder can realize gains or losses and may trigger regulatory reporting, insider rules, or influence over corporate ownership.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What stake does Capital Research Global Investors hold in Magnite (MGNI)?

Capital Research Global Investors reports beneficial ownership of 5,020,289 shares, equal to 3.5% of Magnite's common stock as of 03/31/2026. The filing states sole voting and dispositive power over those shares.

Does the 13G/A filing show voting control for the reported shares?

Yes. The filer discloses sole voting power and sole dispositive power over 5,020,289 shares. The filing lists 0 shares as shared voting or dispositive power.

How many Magnite shares were outstanding per the filing?

The filing states there were 144,364,365 shares believed to be outstanding as of the reporting reference. That outstanding figure is used to calculate the 3.5% ownership percentage.

Who signed the Schedule 13G/A amendment for Capital Research?

The amendment is signed by Jae Won Chung, Vice President and Senior Counsel II of Capital Research and Management Company, with the signature date shown as 05/11/2026.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Accepted by SEC EDGAR 05/14/2026 - 10:19 AM EDT Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 1)

Magnite, Inc.

(Name of Issuer)

Common Stock

(Title of Class of Securities)

55955D100

(CUSIP Number)

03/31/2026

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): 55955D100

1

Names of Reporting Persons

Capital Research Global Investors

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 5,020,289.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 5,020,289.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

5,020,289.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

3.5 %

12

Type of Reporting Person (See Instructions)

IA

SCHEDULE 13G

Item 1.
(a)	Name of issuer: Magnite, Inc.
(b)	Address of issuer's principal executive offices: 1250 Broadway, 9th Floor, New York, NY 10001
Item 2.
(a)	Name of person filing: Capital Research Global Investors
(b)	Address or principal business office or, if none, residence: 333 South Hope Street, 55th Fl, Los Angeles, CA 90071
(c)	Citizenship: N/A
(d)	Title of class of securities: Common Stock
(e)	CUSIP No.: 55955D100
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: 5,020,289 ** **Capital Research Global Investors ("CRGI") is a division of Capital Research and Management Company ("CRMC"), as well as its investment management subsidiaries and affiliates Capital Bank and Trust Company, Capital International, Inc., Capital International Limited, Capital International Sarl, Capital International K.K., Capital Group Private Client Services, Inc., and Capital Group Investment Management Private Limited (together with CRMC, the "investment management entities"). CRGI's divisions of each of the investment management entities collectively provide investment management services under the name "Capital Research Global Investors." CRGI is deemed to be the beneficial owner of 5,020,289 shares or 3.5% of the 144,364,365 shares believed to be outstanding.
(b)	Percent of class: 3.5 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 5,020,289
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: 5,020,289
	(iv) Shared power to dispose or to direct the disposition of: 0
Item 5.	Ownership of 5 Percent or Less of a Class.
	Ownership of 5 percent or less of a class
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	Not Applicable
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	Not Applicable
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Capital Research Global Investors

Signature:	Jae Won Chung
Name/Title:	Vice President and Senior Counsel II, Capital Research and Management Company
Date:	05/11/2026