Starting in December, Yahoo will replace Google as the default search engine for Firefox.
Yahoo and Mozilla signed a five year agreement which so far is only valid for the U.S. but could expand internationally as well.
Yahoo currently has about 10% share in the search market. Bing comes in at 20% while Google still dominates the space with 67% according to comScore.
Firefox itself also has about 10% of the browser market and Yahoo is looking to at incremental users through the new agreement.
No financial details were disclosed.