A Mozilla executive has warned that Firefox's existence is threatened if the browser loses its lucrative search deal with Google, highlighting the browser's dependence on the contract. In a court testimony, Mozilla CFO Eric Muhlheim stated that losing the deal could lead to "significant cuts across the company" and potentially put Firefox out of business.

The warning comes as the US Department of Justice (DOJ) proposes to restrict Google's search monopoly, including barring the company from paying to be the default search engine in third-party browsers like Firefox. The DOJ has already ruled that Google has an illegal monopoly in search, partly due to exclusionary deals that make it the default engine on browsers and phones.

Firefox generates about 90% of Mozilla's revenue, with 85% of that revenue coming from its deal with Google. Losing that revenue would mean Mozilla would have to make significant cuts, which could lead to a "downward spiral" that could ultimately put Firefox out of business. This, in turn, could also impact Mozilla's nonprofit efforts, such as open-source web tools and research on how AI can help fight climate change.

Muhlheim testified that replacing the revenue from Google is not as easy as making a deal with another search engine provider or a non-exclusive deal with Google. Mozilla has talked with Microsoft about the possibility of Bing taking over the default spot, but Muhlheim warned that without Google being able to bid on the contract, the revenue share Mozilla would be able to negotiate would likely fall. Additionally, Mozilla has found that Bing doesn't monetize traffic as efficiently as Google does today.

In a December 2024 presentation to Mozilla's board, the company warned that losing Google's payments posed a "significant threat to viability for Mozilla with limited ability to mitigate." A study conducted by Mozilla in 2021-2022 found that users who switched to Bing generated less revenue for Mozilla, demonstrating what might happen if all of its users were switched over to Bing.

Mozilla has also previously tried to switch all users' default search engines, with disastrous results. Between 2014 and 2017, the company made Yahoo the default on its browser, but users disliked the experience so much that they switched to another browser altogether.

While the DOJ's proposals aim to create more competition in the search engine market, Muhlheim warned that it would likely take a long time for new competitors to emerge, and Mozilla would have to make significant cost cuts and strategy changes in the meantime. "We would be really struggling to stay alive," he said.

On cross-examination, Muhlheim conceded that it would be preferable not to rely on one customer for the vast majority of its revenue, regardless of the court's ruling. He also acknowledged that another browser company, Opera, has already managed to make more money from browser ads than it does from search deals. However, he added that scaling up such a business at Firefox may look different due to the company's privacy-preserving approach to products.

The case highlights the complex relationships between tech companies and the potential consequences of antitrust actions. As the court continues to deliberate, the future of Firefox and the search engine market hangs in the balance.