As others have said, we get revenue from contextual advertising as opposed to behavioural advertising. In other words, if you search for "car" you'd see a car-related ad rather than an ad based on your search history or personal profile (which we don't have anyway).

There's more info about our business model here: https://spreadprivacy.com/duckduckgo-revenue-model/

Disclaimer: DuckDuckGo staff

Advertising.

Untargeted advertising.

There are some ads there. I don't think they have been very successful selling them, but it looks like search is cheaper to provide than it used to be.