Capital Research discloses 9% Magnite (MGNI) stake in Schedule 13G

Rhea-AI Filing Summary

Capital Research Global Investors filed a Schedule 13G showing a passive ownership stake in Magnite, Inc. common stock. It reports beneficial ownership of 12,920,289 shares, representing 9.0% of the class, based on 143,647,869 shares believed outstanding as of 12/31/2025. Capital Research Global Investors has sole voting and dispositive power over all reported shares and certifies the position is held in the ordinary course of business, not to change or influence control of Magnite.

Insights

Equity ownership and governance analyst

Large passive holder reports a 9% stake in Magnite.

Capital Research Global Investors reports beneficial ownership of 12,920,289 Magnite common shares, or 9.0% of the class, as of 12/31/2025. The filing indicates sole voting and dispositive power over the entire position.

The stake is reported on a Schedule 13G, which is used for holdings certified as passive. The filer explicitly states the shares were acquired and are held in the ordinary course of business and not for the purpose of changing or influencing control.

For investors, this reflects a significant institutional presence in Magnite’s shareholder base. Actual impact depends on Capital Research’s ongoing portfolio decisions, but the 13G certification points to a non-activist, long-only style position based on the information provided.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

Magnite, Inc.

(Name of Issuer)

Common Stock

(Title of Class of Securities)

55955D100

(CUSIP Number)

12/31/2025

(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)

SCHEDULE 13G

CUSIP No. 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 12,920,289.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 12,920,289.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

12,920,289.00

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)

9.0 %

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: 12,920,289 ** **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 12,920,289 shares or 9.0% of the 143,647,869 shares believed to be outstanding.
(b)	Percent of class: 9.0 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 12,920,289
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: 12,920,289
	(iv) Shared power to dispose or to direct the disposition of: 0
Item 5.	Ownership of 5 Percent or Less of a Class.
	Not Applicable
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required. SMALLCAP World Fund, Inc.
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:	02/05/2026

FAQ

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

Capital Research Global Investors reports beneficial ownership of 12,920,289 Magnite common shares, representing 9.0% of the outstanding class. This percentage is based on 143,647,869 shares of Magnite common stock believed to be outstanding as of December 31, 2025.

Is Capital Research Global Investors an activist shareholder in Magnite (MGNI)?

No. Capital Research Global Investors filed a Schedule 13G, which is for passive holdings. It certifies the Magnite shares were acquired and are held in the ordinary course of business, not to change or influence control or participate in any control-related transaction.

How much voting power does Capital Research Global Investors have in Magnite (MGNI)?

Capital Research Global Investors reports sole voting power over 12,920,289 Magnite shares and no shared voting power. It also has sole dispositive power over the same number of shares, meaning it alone can decide how to vote and whether to sell them.

Which entities are associated with Capital Research Global Investors’ Magnite (MGNI) stake?

Capital Research Global Investors is a division of Capital Research and Management Company and related investment management affiliates. The filing notes that these investment management entities collectively provide services under the Capital Research Global Investors name and are deemed beneficial owners of the reported Magnite shares.

Does any other fund benefit from Capital Research Global Investors’ Magnite (MGNI) holdings?

Yes. The filing identifies SMALLCAP World Fund, Inc. as a person with the right to receive dividends or sale proceeds from the Magnite shares. This reflects that some or all of the reported holdings are for the benefit of this investment fund’s shareholders.

What triggered Capital Research Global Investors’ Schedule 13G filing for Magnite (MGNI)?

The filing is dated for an event on December 31, 2025, when Capital Research Global Investors’ beneficial ownership reached 9.0% of Magnite’s common stock. Crossing or holding above the 5% ownership threshold generally requires this type of disclosure for passive institutional investors.