Google announced the Privacy Sandbox in 2019 to build a more private web through open standards. The most ambitious aspect is phasing out support for third-party cookies, with Google Chrome now starting a developer test of Federated Learning of Cohorts (FLoC).
Overall, we felt that blocking third-party cookies outright without viable alternatives for the ecosystem was irresponsible, and even harmful, to the free and open web we all enjoy.
Google’s alternative is called Federated Learning of Cohorts, and it has three big tentpoles. FLoC works by grouping thousands of users with similar browsing histories into a “cohort” that’s created by on-device machine learning analyzing your web history. The list of sites you visit does not leave your browser (federated learning), with only the “cohort id” being revealed and used for advertising.
Cohorts are defined by similarities in browsing history, but they’re not based on who you are individually. In fact, which cohort you are in frequently changes as your browsing history changes.
Unlike third-party cookies, individual tracking is not possible with FLoC. Meanwhile, the browser will not create groups that are deemed “sensitive.”
Before a cohort becomes eligible, Chrome analyzes it to see if the cohort is visiting pages with sensitive topics, such as medical websites or websites with political or religious content, at a high rate. If so, Chrome ensures that the cohort isn’t used, without learning which sensitive topics users were interested in.
