Mr. Weinberg started DuckDuckGo in 2008 when he was a stay-at-home dad, after struggling to get two previous start-ups off the ground. The early versions of DuckDuckGo (its name is a nod to the children’s game) did not have any focus on privacy. When he went in that direction, it was attractive to only a small number of privacy advocates.

But after Edward J. Snowden, a former National Security Agency contractor, revealed extensive online surveillance by the United States government in 2013, privacy became a selling point. Business began to grow.

DuckDuckGo is not the only upstart that is trying to capitalize on privacy concerns. Proton Technologies, a Swiss start-up, is taking on Gmail with an alternative email service. The Firefox and Brave browsers are more focused on privacy than Chrome. And Google Maps users can switch to OpenStreetMap.

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DuckDuckGo’s search site looks similar to Google, with the G replaced by a playful cartoon head of a duck, who goes by the name Dax. Type in a question and up pops a list of links that looks like what you’d get from Google, with definitions from Wikipedia at the top and maps supplied through a partnership with Apple Maps.

Mr. Weinberg said the site was designed to make it feel similar to Google, to ease the transition for new users. While DuckDuckGo does not keep data on its users, it can pull the geographic location from each query and serve local results for things like restaurants and news.