Since 2004, Google has been paying Mozilla a ton of money each year—estimated at around $100 million—for the privilege of being the default search engine used in the Firefox browser. This contribution represented the lion's share of Mozilla's income, something in the ballpark of 85 percent.

That deal, last renewed for a three-year period in 2011, has come to an end, and this time it won't be renewed. Mozilla announced today that the free browser vendor is switching to a range of different search providers. In the US, Firefox will now default to using Yahoo (which continues to be powered by Microsoft's Bing engine); in Russia it will use Yandex, and in China, Baidu.

Mozilla and Yahoo have signed a five-year deal. As part of the deal, Yahoo is going to start honoring the Do Not Track feature when used by Firefox users to limit Yahoo's ability to track user activity across the Web through advertisements. Yahoo is also going to roll out a new search interface for American Firefox users, starting in December.

Financial terms of the new five-year deal have not been announced.