Yahoo was using Bing from around 2010 to 2015. But since then they've been using a variety of sources - Bing, Google, and presumably their own, and I think it

Yahoo was using Bing from around 2010 to 2015. But since then they've been using a variety of sources - Bing, Google, and presumably their own, and I think it can mix the results. Yahoo's search business was always odd... They had their own search, then switched to search powered by Google. Then they purchased Overture, which owned AlltheWeb and AltaVista. Overture had originally purchased AlltheWeb from FAST, who had pivoted into the enterprise space, and later got bought by Microsoft and integrated into SharePoint.