They do a combination of their own indexing and using the API of sites like Bing (not sure if I got the second part exactly right, the point is the Bing results

They do a combination of their own indexing and using the API of sites like Bing (not sure if I got the second part exactly right, the point is the Bing results are there with MS's blessing). More discussion of ddg's internals are on the Reddit AMA[1] and the founder's blog[2] [1]http://www.reddit.com/r/IAmA/comments/bbqw7/i_am_the_founder_of_a_search_engine_duck_duck_go/ http://www.reddit.com/r/IAmA/comments/bbqw7/i_am_the_founder... [2] http://www.gabrielweinberg.com/blog/ http://www.gabrielweinberg.com/blog/