• Mozilla warns losing funding could force deep cuts to Firefox.
• The DOJ may push Google to sell Chrome after a court found it holds monopoly.

Mozilla’s Firefox browser could face major financial disruption if a US court moves forward with remedies proposed by the Department of Justice (DOJ) to curb Google’s dominance in the search market, as reported by The Verge. That warning came during testimony on Friday from Mozilla Chief Financial Officer Eric Muhlheim, who appeared as part of the ongoing antitrust trial against Google.

The DOJ is asking the court to prohibit Google from entering into default search engine agreements with third-party browsers, such as the one it has with Firefox. It also proposes a series of broader structural changes, including potentially forcing Google to divest its Chrome browser and requiring it to make its search results available to rivals. The steps follow a ruling that found Google maintains an illegal monopoly in search, achieved partly by paying to be the default engine on browsers and smartphones – deals that limit competition and user choice, the court says

Although Firefox competes with Google’s Chrome, it is also heavily dependent on the very arrangements the DOJ wants to prohibit. According to Muhlheim, Mozilla’s deal with Google provides approximately 85% of the revenue for its for-profit arm, which in turn funds development of Firefox and other products.

Muhlheim testified that losing that income would require Mozilla to make substantial cost reductions in the company. This could affect engineering resources and product development, which in turn might make Firefox less competitive. He warned of a potential downward spiral: if the browser becomes less appealing to users, that could lead to further loss in revenue, endangering the sustainability of the product itself. “That kind of spiral,” he said, “could put Firefox out of business.”

The financial implications go beyond Firefox. Mozilla’s nonprofit foundation also funds open-source tools and research initiatives, including projects exploring how artificial intelligence can support social impact goals like combating climate change. Reduced funding could constrain the organisation’s ability to support these efforts.

The DOJ acknowledged Mozilla’s long-standing advocacy for browser choice and open standards, noting that the company supports choice screens on mobile and desktop operating systems. However, Mozilla does not support a similar approach for default search engines inside browsers. Muhlheim explained that Firefox already provides users with multiple points to select and change their search engine. “There are a thousand different search points in the browser,” he said. “Choice is a core value for us, but context matters. The best way to get to choice is not always a choice screen.”

Mozilla has explored alternatives to the Google partnership in the past. From 2021 to 2022, the company quietly tested changing users’ default search engine from Google to Microsoft’s Bing. An internal study showed that users engaged less with Bing and that the change led to lower revenue. Muhlheim said this data shows the risks Mozilla would face if it could no longer rely on Google as a search partner. In a separate deal from 2014 to 2017, Mozilla made Yahoo! the default search engine, but the user experience led many to abandon Firefox entirely in favour of other browsers.

Mozilla has since held discussions with Microsoft about switching Firefox’s default search engine back to Bing. However, Muhlheim said the company found that Bing doesn’t monetise traffic as efficiently as Google does. Without Google bidding for the default spot, any future deal would likely bring in lower revenue, creating budget constraints for Mozilla.

The proposed remedies by the DOJ are designed to open the market to new competitors and search engines that could, over time, compete for default placement on browsers like Firefox. But Muhlheim said that any meaningful competition would take years to develop, and Mozilla may not be able to bridge the financial gap. “We would be really struggling to stay alive,” he said. The idea of waiting for a “hypothetical future” where alternatives become viable, he added, poses real risks to Firefox’s survival.

During cross-examination, the DOJ highlighted that Mozilla’s heavy reliance on a single customer for most of its revenue poses a risk regardless of the outcome of the case. Muhlheim agreed that a more diverse revenue model would be beneficial. The DOJ also pointed to Opera, another browser company that now earns more from display advertising than from search deals. However, Muhlheim noted that Mozilla’s privacy-focused approach makes such a model harder to scale. Advertising models that rely on extensive data collection do not align with Firefox’s product philosophy.

Judge Amit Mehta asked whether Mozilla would benefit from the emergence of another search provider able to match Google’s quality and revenue potential. “If we were suddenly in that world,” Muhlheim responded, “that would be a world that would be better for Mozilla.”

For now, Mozilla remains caught between regulatory efforts to level the playing field and the practical financial realities of maintaining an independent browser in a market where default positioning remains a powerful financial incentive.