The search engine is written in Perl and runs on nginx, FreeBSD and Linux. DuckDuckGo is built primarily upon search APIs from various vendors. Because of this, TechCrunch characterized the service as a "hybrid" search engine. At the same time, it produces its own content pages, and thus is similar to Mahalo, Kosmix and SearchMe.
Also like other search engines, Google has a large index of keywords and where those words can be found. What sets Google apart is how it ranks search results, which in turn determines the order Google displays results on its search engine results page (SERP).
Yandex is the leading search engine in Russia (by blended market share), and due to recent legal changes (Google got slapped in Russian courts), they’ve also closed the gap on mobile. More than just a search engine, Yandex also provide a browser (YaBrowser), email, news, maps, paid advertising, and translator services to the Russian market, as well as in Belarus, Kazakhstan, the Ukraine, and Turkey.