The Federated Learning of Cohorts or FLoC is promoted to be a better strategy that protects people’s privacy while still giving advertisers something they can profit.

FLoC trades individual user tracking and fingerprinting for group identification based on similar browsing histories of members in that group. Google argues that it is more private since advertisers and sites only see group IDs and the browsing history data never leaves the device. Google also promises that it won’t create cohorts that are associated with sensitive topics to ensure the security and privacy of members of that group.

FLoC collects more private data in the form of browsing history, something that even tracking cookies don’t do. While unique individual identities might be hidden behind cohorts, the data held by browsing history can still be considered as something private, especially when it will be easy to develop profiles for members of that group.

Brave and Vivaldi have published rather scathing posts about FLoC and have promised to block it in any form. Brave will additionally block FLoC interaction for Chrome users visiting its website.

Google’s FLoC is,only applicable to its own Chrome browser but apparently also has traces in the open source Chromium engine that is used by Brave, Vivaldi, Microsoft Edge, and many other smaller browsers

Google’s replacement for third-party tracking cookies is already under legal scrutiny, When Chrome completely blocks such cookies, advertisers and sites may be forced to switch to FLoC and Google’s advertising platform to continue making a living from ads on Chrome browsers. Brave, points out that FLoC may actually be harmful even for sites and advertisers as its system will favor larger entities that can steal audiences away from niche or smaller players.