You might be surprised to learn that your ability to choose Firefox as your browser could be at risk. Mozilla, the company behind Firefox, says it could be forced to shut down its browser if the courts stop Google from paying to be its default search engine.
On May 3, Mozilla’s Chief Financial Officer, Eric Muhlheim, testified in court that the US Department of Justice’s (DOJ) proposed restrictions on Google’s business could seriously affect Firefox. One key proposal would stop Google from paying browser companies, like Mozilla, to make Google the default search engine. If this happens, Mozilla might lose the majority of its income.
“It’s very frightening,” said Muhlheim during the testimony. He explained that about 85% of Mozilla’s income comes from a deal with Google, where Google pays to be the default search engine in Firefox. Since this deal makes up nearly 90% of Mozilla’s overall revenue, losing it would mean huge cuts across the company. This would affect product development and innovation — and could even mean the end of Firefox.
Cuts could lead to a downward spiral
If Mozilla loses this deal, it won’t just be a matter of earning less money. Muhlheim explained that the company would be forced to cut back on staff and investment in Firefox. That would make the browser less appealing to users, causing more people to leave it. This, in turn, would lead to further loss of income — creating what Muhlheim called a “downward spiral.”
He warned that such a spiral could “put Firefox out of business.” That would also hurt Mozilla’s nonprofit work, including projects to make the internet more open and fight climate change through AI. It could reduce funding for other tools and services you may not even realise come from Mozilla, such as privacy-focused web tools and independent research.
What makes Firefox unique is that it uses its own browser engine, Gecko—the only major engine not owned by a tech giant. Google runs Chromium, and Apple runs WebKit. Gecko ensures that the web remains open and not controlled by one company. Muhlheim reminded the court that Mozilla created Gecko to avoid a situation where one browser, like Microsoft’s in the past, controlled everything on the web.
Replacing Google isn’t simple
You may wonder why Mozilla doesn’t just find another search engine partner, like Bing. Mozilla has spoken with Microsoft about making Bing the default search engine in Firefox. However, without Google in the bidding process, any deal Mozilla strikes would likely bring in less money. Muhlheim added that Bing doesn’t generate as much revenue for Firefox as Google does.
From 2021 to 2022, Mozilla tested switching users from Google to Bing without announcing it. The results weren’t great — revenue dropped. Mozilla also tried a similar change years ago, switching to Yahoo between 2014 and 2017. However, many users were unhappy and switched to different browsers altogether.
According to a December 2024 board presentation in court, Mozilla warned that losing its deal with Google was a “significant threat to viability.” The presentation said there would be “limited ability to mitigate. “
Even if the DOJ’s plan successfully creates more search engine competition, that might take years. During that time, Mozilla would need to make major cuts to stay afloat. Muhlheim said, “We would be struggling to stay alive.”
Mozilla seeks long-term solutions
While testifying, Muhlheim admitted that relying on one partner for most of the company’s income isn’t ideal. He noted that another browser company, Opera, earns more from advertising than search deals. But Firefox’s focus on privacy means building that kind of business may be harder.
Mozilla has supported giving users more choices when they install browsers on their phones and computers — something that could help Firefox. But it doesn’t support a choice screen for picking a search engine inside the browser itself. Muhlheim explained that Firefox already offers users many ways to switch search engines. “There are a thousand different search points in the browser,” he said. “Choice is a core value for us, but context matters.”
The judge in the case, Amit Mehta, asked Muhlheim if Mozilla would benefit if at least one of the DOJ’s ideas went through. The answer seemed to be yes — but only if Firefox can survive long enough to see that future.
