Other Events. On August 6, 2026, A10 Networks, Inc. filed a prospectus supplement to its automatic shelf registration statement on Form S-3 (Registration No. 333-298099) with the Securities and Exchange Commission. This Current Report on Form 8-K is being filed solely for the purpose of filing the opinion of Pillsbury Winthrop Shaw Pittman LLP relating to the legality of the issuance and sale of the securities set forth in the prospectus supplement, which opinion is attached as Exhibit 5.1 he…

Other Events. On August 5, 2026, the Company announced that its Board of Directors (the “Board”) approved a quarterly dividend. The quarterly dividend, in the amount of $0.06 per share, will be payable, subject to any prior revocation, on September 1, 2026 to stockholders of record on August 17, 2026. Future dividends will be subject to further review and approval by the Board in accordance with applicable law. The Board reserves the right to adjust or withdraw the quarterly dividend in futur…

Entry into a Material Definitive Agreement. Warrant On August 3, 2026, A10 Networks, Inc. (the "Company") issued a warrant (the "Warrant") to Microsoft Corporation ("Microsoft") pursuant to which Microsoft may purchase up to 800,000 shares of the Company's common stock, par value $0.00001 per share (the "Warrant Shares"), at an exercise price of $0.01 per share, subject to the terms and conditions of the Warrant. The Warrant was issued in connection with certain commercial arrangements betwee…

Unregistered Sales of Equity Securities. The information set forth in

Results of Operations and Financial Condition On August 5, 2026, A10 Networks, Inc. (the “Company”) issued a press release regarding financial results for the quarter ended June 30, 2026. A copy of the press release is furnished herewith as Exhibit 99.1.

Executive Vice President, Worldwide Sales and Marketing — Sheen Khoury: Mr. Khoury was terminated from his position.

Executive Vice President, Worldwide Sales and Marketing — Sheen Khoury: Mr. Khoury was terminated from his position.

Other Events. On April 28, 2026, the Company announced that its Board of Directors (the “Board”) approved a quarterly dividend. The quarterly dividend, in the amount of $0.06 per share, will be payable, subject to any prior revocation, on June 1, 2026 to stockholders of record on May 15, 2026. Future dividends will be subject to further review and approval by the Board in accordance with applicable law. The Board reserves the right to adjust or withdraw the quarterly dividend in future period…

Results of Operations and Financial Condition On April 28, 2026, A10 Networks, Inc. (the “Company”) issued a press release regarding financial results for the quarter ended March 31, 2026. A copy of the press release is furnished herewith as Exhibit 99.1.

contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Exchange Act, including statements regarding the Company’s dividend program. These forward-looking statements involve risks and uncertainties. These forward-looking statements may be identified by terms such as “will,” “may,” “plans,” or the negative of these terms, and similar expressions intended to identify forward-looking statements. These forward-looking…

Results of Operations and Financial Condition On February 4, 2026, A10 Networks, Inc. (the “Company”) issued a press release regarding financial results for the quarter and year ended December 31, 2025. A copy of the press release is furnished herewith as Exhibit 99.1.

contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Exchange Act, including statements regarding the Company’s dividend program. These forward-looking statements involve risks and uncertainties. These forward-looking statements may be identified by terms such as “will,” “may,” “plans,” or the negative of these terms, and similar expressions intended to identify forward-looking statements. These forward-looking…

Results of Operations and Financial Condition On November 4, 2025, A10 Networks, Inc. (the “Company”) issued a press release regarding financial results for the quarter ended September 30, 2025. A copy of the press release is furnished herewith as Exhibit 99.1.

CFO — Brian Becker: The CFO resigned but an immediate external successor was appointed with a transition plan, indicating an orderly succession rather than a sudden loss of leadership.

Results of Operations and Financial Condition On August 5, 2025, A10 Networks, Inc. (the “Company”) issued a press release regarding financial results for the quarter ended June 30, 2025. A copy of the press release is furnished herewith as Exhibit 99.1.

contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Exchange Act, including statements regarding the Company’s dividend program. These forward-looking statements involve risks and uncertainties. These forward-looking statements may be identified by terms such as “will,” “may,” “plans,” or the negative of these terms, and similar expressions intended to identify forward-looking statements. These forward-looking…

contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Exchange Act, including statements regarding the Company’s dividend program. These forward-looking statements involve risks and uncertainties. These forward-looking statements may be identified by terms such as “will,” “may,” “plans,” or the negative of these terms, and similar expressions intended to identify forward-looking statements. These forward-looking…

Results of Operations and Financial Condition On May 1, 2025, A10 Networks, Inc. (the “Company”) issued a press release regarding financial results for the quarter ended March 31, 2025. A copy of the press release is furnished herewith as Exhibit 99.1.

The Notes (including the Additional Notes) were issued to the initial purchasers in reliance upon Section 4(a)(2) of the Securities Act of 1933, as amended (the “Securities Act”), in transactions not involving any public offering. The Notes (including the Additional Notes) were resold by the initial purchasers to persons whom the initial purchasers reasonably believe are “qualified institutional buyers,” as defined in, and in accordance with, Rule 144A under the Securities Act. Any shares of…

Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant. On March 20, 2025, A10 Networks, Inc. (the “Company”) issued $25,000,000 aggregate principal amount (the “Additional Notes”) of its 2.75% Convertible Senior Notes due 2030 (the “Notes”) in a private offering pursuant to the exercise in full of the previously announced option the Company granted to the initial purchasers of the Notes. The Notes (including the Additional Notes) wer…

Creation of a Direct Financial Obligation or an Off-Balance Sheet Arrangement. The disclosure set forth in

Entry Into or Amendment of a Material Definitive Agreement. On March 17, 2025, the Company issued $200,000,000 principal amount of its 2.75% Convertible Senior Notes due 2030 (the “Notes”). The Notes were issued pursuant to, and are governed by, an indenture (the “Indenture”), dated as of March 17, 2025, between the Company and U.S. Bank Trust Company, National Association, as trustee (the “Trustee”). Pursuant to the purchase agreement between the Company and the representative of the initial…

The Notes were issued to the initial purchasers in reliance upon Section 4(a)(2) of the Securities Act of 1933, as amended (the “Securities Act”), in transactions not involving any public offering. The Notes were resold by the initial purchasers to persons whom the initial purchasers reasonably believe are “qualified institutional buyers,” as defined in, and in accordance with, Rule 144A under the Securities Act. Any shares of the Company’s common stock that may be issued upon conversion of t…

Creation of a Direct Financial Obligation or an Off-Balance Sheet Arrangement. The disclosure set forth in

Entry Into or Amendment of a Material Definitive Agreement. On March 17, 2025, A10 Networks, Inc. (the “Company”) issued $200,000,000 principal amount of its 2.75% Convertible Senior Notes due 2030 (the “Notes”). The Notes were issued pursuant to, and are governed by, an indenture (the “Indenture”), dated as of March 17, 2025, between the Company and U.S. Bank Trust Company, National Association, as trustee (the “Trustee”). Pursuant to the purchase agreement between the Company and the repres…