Yahoo and Mozilla are suing each other after their big search partnership fell apart

Yahoo and Mozilla, the maker of the Firefox web browser, are embroiled in a legal fight over a 2014 deal that made Yahoo the default search engine for Firefox users in the US.

The search partnership, which was worth hundreds of millions of dollars a year and was supposed to run through 2019, was one of the biggest deals struck by former Yahoo CEO Marissa Mayer and raised hopes that the pioneering web portal might be able to revive its business.

But Yahoo has since been acquired by Verizon. And in the eyes of Mozilla, that was grounds to terminate the agreement. Mozilla dumped Yahoo as the default search engine earlier this year, replacing it with Google.

Now, both companies are suing each other.

"We recently exercised our contractual right to terminate our agreement with Yahoo based on a number of factors including doing what’s best for our brand, our effort to provide quality web search, and the broader content experience for our users," Mozilla wrote in a blog post on Tuesday evening.

Mozilla said that Yahoo and Oath, the name of the Verizon subsidiary that Yahoo now operates under, sued Mozilla on December 1 on the grounds that it improperly terminated the agreement. Mozilla hit back on December 5 with a cross-complaint arguing that it was protecting its rights to enforce the contract.

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