DDG does have their own index, but also use Bing and many other sources. See the CEO's numerous comments to that effect: https://hn.algolia.com/?dateRange=all&

DDG does have their own index, but also use Bing and many other sources. See the CEO's numerous comments to that effect: https://hn.algolia.com/?dateRange=all&page=0&prefix=false&query=by%3Ayegg%20index%20&sort=byPopularity&type=comment https://hn.algolia.com/?dateRange=all&page=0&prefix=false&qu..., https://hn.algolia.com/?dateRange=all&page=0&prefix=true&query=by%3Aepi0Bauqu%20index%20&sort=byPopularity&type=comment https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...