Explainer: FLoC – Google's proposed alternative for third-party cookies

While promising, FLoC has come under criticism and scrutiny. 

Google earlier announced that it will phase out third-party cookies from its web browser. Moreover, it will not build alternative identifiers to track individuals.

While it was anticipated that Google Chrome will be removing third-party cookies by next year, on June 24, the company announced an updated timeline where it delayed plans to phase out third-party cookies until 2023.

On a blog titled ‘An updated timeline for Privacy Sandbox milestones,’ Vinay Goel, privacy engineering director for Chrome, cited numerous reasons for the delay. But the foremost reason for the new timeline is Chrome’s decision to end the initial trial of its proposed alternative for third-party cookies, Federated Learning of Cohorts (FLoC). It is being developed as a part of Google's Privacy Sandbox initiative.

What is FLoC?

FLoC is a type of web tracking that groups people into “cohorts” based on their browsing history for interest-based advertising.

The algorithm analyses users' online activity within the browser, and generates a "cohort ID" using the SimHash algorithm to group a given user with other users who access similar content.

Each cohort contains several thousand users in order to make identifying individual users more difficult, and cohorts are updated weekly. Websites are then able to access the cohort ID using an API and determine what advertisements to serve.

Google does not label cohorts based on interest beyond grouping users and assigning an ID, so advertisers need to determine the user types of each cohort on their own.

While promising, FLoC as an alternative has come under criticism and scrutiny. 

Opposition to FLoC

The technology has been criticised on privacy grounds by groups including the Electronic Frontier Foundation and DuckDuckGo, and has been described as anti-competitive. It has generated an antitrust response in multiple countries as well as questions about General Data Protection Regulation compliance.

Aside from the security concerns related to FLoC, given the dominance of Chrome browser, the real issue is that Google is using its dominance in the browser market to extend dominance in the internet ad market as well as a result of the combined effect of the moves (phasing out third party cookies + FLoC).

There is the added risk of google turning into a gatekeeper.

Our point of view at ADIF

It’s heartening to see that conversations and explorations are happening around finding better alternatives to third-party cookies, ones that respect both user’s need for privacy and personalisation.

FLoC could be one of the solutions in that direction – the litmus test would be whether or not such solutions pass the GDPR test.

But if FLoC gets implemented unilaterally by Google as a system, it would pose its own set of challenges. Google already has a monopoly on search and browser through Chrome, and with FLoC, there’s a danger of Google becoming the gatekeeper and that would give it more market dominance, which would put other players in the internet economy at a disadvantage. That’s a major area of concern for us.

The choice of third-party cookies or FLoC should thus be left to marketplaces and not exclusively to Google.


Should you have any thoughts on Google’s FLoC, please share in the comments section or write to Tom Thomas, who heads Policy and Research at ADIF, at tom@adif.in.

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