Mozilla Tells Appeals Court Its Google Search Deal Carried No Exclusivity Requirement

Mozilla told a federal appeals court that its revenue-sharing agreement with Google to make Google the default search engine in Firefox carried no express or implied exclusivity requirement.

The company filed a friend-of-the-court brief pushing back on part of the lower court’s ruling in the U.S. government’s antitrust case against Google, according to a report by MLex, which first covered the filing.

What Mozilla Is Arguing

Mozilla’s central claim is that Firefox users retain the freedom to switch their default search engine, and that this choice distinguishes the arrangement from a true exclusivity deal.

The company cited its own history as evidence. From 2014 to 2017, Yahoo held the default search slot in Firefox — not Google.

Mozilla also pointed to testimony from its chief financial officer, who said users actively moved away from Yahoo Search during that period because they were dissatisfied with it, according to MediaPost. That user behavior, Mozilla argues, shows default placement does not lock out rivals when users can and do exercise their choice.

Revenue at Stake

The filing carries direct financial weight for Mozilla. Google’s payments for default search placement in Firefox have long represented a substantial share of Mozilla’s annual revenue.

Mozilla has warned publicly for months that stripping away those payments could undermine its capacity to maintain Gecko, the proprietary browser rendering engine that powers Firefox. Chromium, the open-source engine backed by Google, underpins nearly every other major browser — making Firefox and Gecko among the last independent alternatives at scale.

In a blog post last year, Mozilla said banning search revenue-sharing agreements with independent browsers could put Gecko’s continued development at risk. It also argued that courts should avoid damaging browser competition while attempting to remedy search competition.

The Broader Antitrust Context

U.S. District Judge Amit Mehta ruled last year that Google illegally maintained a monopoly in the general search market, in part by paying billions of dollars annually to device makers and browser developers to secure default search placement. The U.S. Department of Justice has since proposed remedies that could restrict or ban such payments.

Google is appealing that ruling. The remedies phase of the case continues to move through the courts, with the outcome potentially reshaping how search engines reach users across devices and browsers.

Mozilla’s position draws a line between payments that foreclose competition and payments that simply purchase a prominent starting point — one that users can override. Whether the appeals court accepts that distinction could shape how broadly any eventual remedy applies.

Firefox holds roughly 2.5% to 3% of the global browser market, according to data tracked by StatCounter, a web analytics service. Chrome commands more than 65%.