Mozilla told a federal appeals court late last week that its Firefox search deal with Google never contained an exclusivity clause, asking the D.C. Circuit to overturn one of U.S. District Judge Amit Mehta's central antitrust findings against Google.

In a friend-of-the-court brief, Mozilla argued that Mehta wrongly characterized the agreement as "exclusive" when he ruled in 2024 that Google violated antitrust law. The 10-week trial produced findings that Google's status as the default search engine on Mozilla's Firefox, Apple's Safari, and Android devices allowed it to maintain a monopoly in two markets: general search services and search text ads.

What does Mozilla say about the contract?

Mozilla's filing states: "Mozilla ensured that the agreement never contained any express or implicit exclusivity requirement." The company also says trial evidence "irrefutably establishes that Mozilla selected Google as the Firefox search default based on product quality and user preference."

The brief is filed "in support of neither party and reversal," meaning Mozilla contests only Mehta's exclusivity finding, not the broader question of whether Google's other default arrangements broke the law.

Why is the 2014-2017 Yahoo deal relevant?

Mozilla points to a prior arrangement under which Yahoo served as the default search engine for Firefox from 2014 to 2017. The company argues that episode proves "non-default search engines can compete for and win significant percentages of Firefox search traffic."

Mozilla's former chief financial officer testified at trial that Firefox users "did not like the Yahoo Search experience" and shifted away from the default toward another provider. Mozilla now frames that shift as evidence the market stayed open rather than locked, and that rivals retained the ability to win users even when they were not the default.

How has Google responded on appeal?

Google filed its own appellate papers last month, arguing that Mozilla and Apple chose Google as their default "for the procompetitive reason of improving their users' experience." Mehta had written that the default deals "establish Google as the out-of-the-box default search engine" and held that the exclusive nature of the agreements had anticompetitive effects in both the general search and search advertising markets.

The judge's findings have become a focal point for both sides because exclusivity lies at the heart of the monopolization claim. If the D.C. Circuit narrows or removes that finding, downstream questions about remedies, divestiture, and behavioral penalties shift in scope.

What happens next in the case?

The U.S. Department of Justice and the state plaintiffs are expected to file their appellate briefs in July. The D.C. Circuit will then weigh Mozilla's narrow challenge alongside Google's broader appeal of Mehta's liability findings.

For search marketers, publishers, and SEO professionals, the procedural posture matters because remedies hearings and the eventual appellate outcome will shape which default slots and revenue-sharing terms Google can offer browser partners going forward. Browser competition, mobile search choice screens, and Android defaults remain the most exposed categories if Mehta is upheld in full.

Watch how the D.C. Circuit treats the Mozilla brief, and whether DOJ's July filing embraces or distances itself from Mehta's "exclusive" language. The court's framing on either point will shape how default-search contracts get written for the rest of this decade.