Filing of Certain Prospectuses and Communications in Connection With Business Combination Transactions (425)

Filed by Unity Software Inc.

pursuant to Rule 425 under the U.S. Securities Act of 1933, as amended,

and deemed filed pursuant to Rule 14a-12

under the Securities Exchange Act of 1934, as amended

Subject Company: ironSource Ltd.

Commission File No.: 001-40539

On July 27, 2022, Unity Software Inc. (the “Company”) provided the following “Q&A” to employees with regard to the Company’s merger with IronSource Ltd.:

Q: Why did we value them at a 74% premium over the 30 day trading average prior to merging with them? Why was convert note pursued as a PIPE vs. a public q144a/reg s deal? How was 2% coupon derived?

A: Great question. There were many factors considered in the valuation. One is premium vs. their current valuation (which is common practice) the other key factor is the contribution of each of the businesses in terms of revenue, earnings, and free cash flow. They contribute over 100% of the combined company’s earnings and free cash flow.

Cautionary Statement Regarding Forward-Looking Statements

This communication includes forward-looking statements. These forward-looking statements generally can be identified by phrases such as “will,” “expects,” “anticipates,” “foresees,” “forecasts,” “estimates” or other words or phrases of similar import. These statements are based on current expectations, estimates and projections about the industry and markets in which Unity Software Inc. (“Unity”) and ironSource Ltd. (“ironSource”) operate and management’s beliefs and assumptions as to the timing and outcome of future events, including the transactions described in this communication. While Unity’s and ironSource’s management believe the assumptions underlying the forward-looking statements are reasonable, such information is necessarily subject to uncertainties and may involve certain risks, many of which are difficult to predict and are beyond management’s control. These risks and uncertainties include, but are not limited to the expected timing and likelihood of completion of the proposed transaction, including the timing, receipt and terms and conditions of any required governmental and regulatory approvals of the proposed transaction; the occurrence of any event, change or other circumstances that could give rise to the termination of the merger agreement; the outcome of any legal proceedings that may be instituted against the parties and others following announcement of the merger agreement; the inability to consummate the transaction due to the failure to obtain the requisite stockholder approvals or the failure to satisfy other conditions to completion of the transaction; risks that the proposed transaction disrupts current plans and operations of Unity and ironSource; the ability to recognize the anticipated benefits of the transaction, including anticipated synergies; the amount of the costs, fees, expenses and charges related to the transaction; Unity’s expected stock buyback occurring as planned or at all; and the other risks and important factors contained and identified in Unity’s and ironSource’s filings with the Securities and Exchange Committee (“SEC”), such as Unity’s Annual Report on Form 10-K for the fiscal year ended December 31, 2021 and subsequent Quarterly Reports on Form 10-Q and Current Reports on Form 8-K, and ironSource’s Annual Report on Form 20-F for the fiscal year ended December 31, 2021 and subsequent Current Reports on Form 6-K, any of which could cause actual results to differ materially from the forward-looking statements in this communication.

There can be no assurance that the proposed transaction will in fact be consummated. We caution investors not to unduly rely on any forward-looking statements. The forward-looking statements speak only as of the date of this press release. Neither Unity nor ironSource is under any duty to update any of these forward-looking statements after the date of this communication, nor to conform prior statements to actual results or revised expectations, and neither Unity nor ironSource intends to do so.

Important Information for Investors and Stockholders

In connection with the proposed transaction, Unity expects to file with the SEC a registration statement on Form S-4 that will include a joint proxy statement of Unity and ironSource that also constitutes a prospectus of Unity, which joint proxy statement/prospectus will be mailed or otherwise disseminated to Unity’s and ironSource’s respective

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securityholders, as applicable, when it becomes available. Unity and ironSource also plan to file other relevant documents with the SEC regarding the proposed transaction. INVESTORS ARE URGED TO READ THE JOINT PROXY STATEMENT/PROSPECTUS AND OTHER RELEVANT DOCUMENTS FILED WITH THE SEC IF AND WHEN THEY BECOME AVAILABLE, BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION.

Investors and securityholders may obtain free copies of the registration statement and the joint proxy statement/prospectus (if and when it becomes available) and other relevant documents filed by Unity and ironSource with the SEC at the SEC’s website at www.sec.gov. Copies of the documents filed by the companies will be available free of charge on their respective websites at www.unity.com and www.is.com.

Participants in Solicitation

Unity, ironSource and their respective directors and executive officers may be considered participants in the solicitation of proxies in connection with the proposed transaction. Information about the directors and executive officers of Unity is set forth in its proxy statement for its 2022 annual meeting of stockholders, which was filed with the SEC on April 20, 2022. Information about the directors and executive officers of ironSource is set forth in its Annual Report on Form 20-F for the fiscal year ended December 31, 2021, which was filed with the SEC on March 30, 2022. These documents can be obtained free of charge from the sources indicated above. Additional information regarding the participants in the proxy solicitations and a description of their direct and indirect interests, by security holdings or otherwise, will be contained in the joint proxy statement/prospectus and other relevant materials to be filed with the SEC when they become available.

No Offer or Solicitation

This communication is not intended to and shall not constitute an offer to sell or the solicitation of an offer to sell or the solicitation of an offer to buy any securities or a solicitation of any vote of approval, nor shall there be any sale of securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction. No offer of securities shall be made except by means of a prospectus meeting the requirements of Section 10 of the Securities Act of 1933, as amended.