What you need to know Vivaldi, Mozilla, and Brave have come out with strong statements against Google's FLoC. FLoC uses your data to place you into groups for the purpose of advertising. Microsoft also commented on FLoC, and appears to be against it. It turns out that browsers of a feather don't flock together. Brave, Vivaldi, Microsoft, and Mozilla have all come out against Google's FLoC (Federated Learning of Cohorts). The controversial technology is criticized by several companies due to privacy concerns. FLoC looks at your browser history with an algorithm and puts you into a group of people with similar histories for the purposes of advertising. It's a complicated technology that many browser makers have come out against. As pointed out by The Verge Google seems to be the only browser maker that plans to use FLoC.