[ry_co]

Regarding DuckDuckGo, my understanding is that though they have their own web crawler, most of the information is coming from Bing and Yahoo, who are the only direct competitors to Google.

[bduerst]

You're mostly correct.

Yahoo has been Bing for years, and DuckDuckGo pulls from Bing and Yandex - the latter being mostly for searches in Russian.

[ColinHayhurst]

I concur. https://www.searchenginemap.com/