Federated Learning of Cohorts (FLoC) will be deployed as a developer origin trial in Google Chrome and will be tested with a small percentage of users in Australia, Brazil, Canada, India, Indonesia, Japan, Mexico, New Zealand, the Philippines and the US.

The trial of FLoC comes as Google Chrome prepares to phase out third-party cookies as part of attempts to increase data privacy, a policy that has also been adopted by other leading internet browsers. Third-party cookies are widely used by many advertisers to target their advertising effectively.

FLoC works by allowing internet users’ browsers to use the FLoC algorithm to work out an “interest cohort”, according to Google, which will be the same for thousands of other browsers which all have similar recent browsing histories.

The browser will recalculate the cohort periodically on the users’ device without sharing individual data with the browser’s vendor or other third parties.

Advertisers can then include a code on their websites that gathers and provides cohort data to their adtech platforms, and can use this data to select relevant advertisements when a browser from the relevant cohort requests a page from a website that displays advertising.

A blog post by Marshall Vale, product manager, Privacy Sandbox, at Google, said FLoC would ensure users remain anaonymous as part of a cohort and that FLoC would not share users’ browsing history with other parties, including Google.

The company also said it would not create cohorts that it deems “sensitive”, such as visiting certain medical websites or websites with political or religious content, without a prior investigation.

Google has been working on an open-source Privacy Sandbox since 2019 to make third-party cookies obsolete while also allowing cookie-based advertising.

Vale wrote in the blog: “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.”