Yahoo is the new default search engine on the Firefox web browser in the US ousting Google.
The five-year deal ends Google’s decade-old partnership with the Mozilla Foundation.
Yahoo says it will unveil a new search engine on Firefox in December and continue the roll-out on its own website in early 2015.
The financial details of the union have yet to be announced.
The move signals Yahoo’s resolve to regain ground in the lucrative internet advertising market.