In a Whonix forum a person alleged that DuckDuckGo was using browser fingerprinting techniques to track people. The search engine denies the claim however.
“Fingerprinting-detection libraries unfortunately create false positives because they don’t anticipate good actors using some browser APIs for non-nefarious purposes for which they were designed. We know this not only because we’re falsely identified here (and have been elsewhere) but because we are building this type of detection into our mobile app and browser extension and don’t similarly want to make false claims.”
DuckDuckGo CEO Gabe Weinberg said an API they use to determine the size of the browser might be triggering the fingerprinting flag.