DuckDuckGo: A privacy-conscious search engine

> Although no details are given, DDG claims to redirect a search request
> "in such a way so that it does not send your search terms to other sites.
> The other sites will still know that you visited them, but they will not
> know what search you entered beforehand."

This is achieved by passing the search query as POST data, which does not appear in the Referrer HTTP header sent by web browser.