DuckDuckGo markets itself as a privacy centric business. It offers a "privacy" focused webbrowser and a search engine. The search engine does not track your searches or your behavior while performing searches. Furthermore, instead of building user profiles to display interest-based advertisements, DuckDuckGo uses contextual advertisements from partners, like Ads by Microsoft.
It turns out that DuckDuckGo was not fully transparent (see link). As a part of its search engine deal with Microsoft, it was required to permit Microsoft to track your IP address and other information when clicking on an ad link for "accounting purposes" in the DuckDuckGO browser.
Image from Kevin Gedge on Unsplash