Google is experimenting with an ad targeting technology called FLoC (pronounced "flock") that uses Chrome to analyze users' browsing histories and place them into groups with similar browsing habits. The tech giant says FLoC, which stands for a “Federated Learning of Cohorts,” could replace third-party cookies, and says “advertisers can expect to see at least 95% of the conversions per dollar spent when compared to cookie-based advertising,” for reaching in-market and affinity audiences.

“Instead of understanding browsing behavior or interests at an individual level, the intent here is to have groups of users who would have similar interests,” said Chetna Bindra, group product manager, user trust and privacy at Google. The advancement comes as Google, Apple and other companies scramble to find a replacement for third-party cookies, and as users push for more privacy on the web through new regulations like the CPRA.  

FLoC uses an algorithm built into the Chrome web browser that observes what websites a user visits. The algorithm then uses that browsing information to put the user into a cohort, a group of thousands of other users with similar browsing habits. That cohort can then be used by publishers and advertisers to serve up targeted ads.

Key to FLoC is preserving user privacy by using identifiers for groups rather than for individuals. 

Google says the FLoC proposal shares only the cohort group to advertisers, and does not share any information the browser uses to arrive at the cohort, like a user’s browsing history. The groups are also large enough to make identifying an individual unlikely, and a cohort can be updated over time as the user browses the internet.

For advertisers, Google says the technology needed to target FLoC cohorts should be similar to existing solutions currently on the market. FLoC-based cohorts will be available for public testing through origin trials with a March update to Chrome. Origin trials are a way to test new or experimental web platform features and give feedback before a feature is made available to all users. Google says it expects to begin testing FLoC-based cohorts with advertisers in Google Ads in Q2. The company also plans to roll out controls for the Privacy Sandbox in April that effectively work to opt users in or out.

Google cautions that the technology is still in an early stage and is only one of several other solutions meant to comply with the Privacy Sandbox, a set of proposals for ad tracking while preserving user privacy. However, Google says FLoC is “at the leading edge” of the current proposals, says Bindra.