Waterfox is a fork of the Firefox web browser, which comes in two versions: Waterfox G (the up-to-date one) and Waterfox Classic (which still supports Firefox’s old XUL architecture, but has security issues). It was first released by Alex Kontos in 2011, is FOSS, and aims to be a more privacy-focused version of Firefox. Waterfox G currently tracks the Firefox Extended Support Releases.

In late 2019, it was sold to “privacy-focused” advertising company System1, which is also a majority owner of the search engine StartPage. This was something which did not come to public attention until February the following year. Liz McIntyre posted a Reddit thread in /r/privacy(external link) when she found out about the sale. The story was picked up by ghacks(external link), and Alex Kontos published a blog post explaining his decision(external link) later that day. Kontos still works actively developing the Waterfox browser.