Federated Learning of Cohorts (FLoC) is a type of web tracking. It groups people into "cohorts" based on their browsing history for the purpose of interest-based advertising.[1][2] FLoC was being developed as a part of Google's Privacy Sandbox initiative,[3] which includes several other advertising-related technologies with bird-themed names.[1][4]: 48 Despite "federated learning" in the name, FLoC does not utilize any federated learning.[5]
Google began testing the technology in Chrome 89[6] released in March 2021 as a replacement for third-party cookies. By April 2021, every major browser aside from Google Chrome that is based on Google's open-source Chromium platform had declined to implement FLoC. The technology was criticized on privacy grounds by groups including the Electronic Frontier Foundation and DuckDuckGo, and has been described as anti-competitive; it generated an antitrust response in multiple countries as well as questions about General Data Protection Regulation compliance. In July 2021, Google quietly suspended development of FLoC;[7] Chrome 93,[8] released on August 31, 2021, became the first version which disabled FLoC, but did not remove the internal programming.[9]
On January 25, 2022, Google officially announced it had ended development of FLoC technologies and proposed the new Topics API to replace it.[10][11]Brave developers criticized Topics API as a rebranding of FLoC with only minor changes and without addressing their main concerns.[12]