We can infer some things about DDG based published data on crawler and bot activity. DDG's index is pretty comparable to both Google and Bing, but their bot is

We can infer some things about DDG based published data on crawler and bot activity. DDG's index is pretty comparable to both Google and Bing, but their bot is no where to be found in activity stats. So it's pretty reasonable to think that at minimum their index is primarily derived from 3rd parties. https://deviceatlas.com/blog/most-active-bots-and-crawlers-web https://deviceatlas.com/blog/most-active-bots-and-crawlers-w... https://www.imperva.com/blog/most-active-good-bots/ https://www.imperva.com/blog/most-active-good-bots/ In my opinion, I don't think it should matter too much that they might not be crawling for their own index as long as they're reordering the results. But I do think there is some stigma where metasearch engines aren't looked at with as much prestige.