Multiple browser makers, including the Mozilla Foundation, have indicated that they don’t currently plan to adopt Google LLC’s FLoC privacy system.

FLoC, which stands for Federated Learning of Cohorts, is intended as a replacement to the third-party cookies that online advertisers use to deliver personalized promotions. 

Mozilla, the maker of Firefox, said that it has “no current plans” to implement FLoC in a Thursday statement to Digiday. Browser makers Vivaldi Technologies AS and Brave Software Inc. earlier both rejected the technology, arguing it does not improve privacy as Google claims. And The Verge reported today that Microsoft Corp., whose Edge browser competes with Chrome, didn’t commit either to implementing or to blocking FLoC when asked about the matter. 

“The industry is on a journey and there will be browser-based proposals that do not need individual user IDs and ID-based proposals that are based on consent and first party relationships,” a Microsoft spokesperson was quoted as saying. “We will continue to explore these approaches with the community.”

FLoC is a browser-based system aimed at improving online privacy by removing the need for third-party cookies. Third-party cookies are small files that advertisers use to collect information about users’ online activity so they can target them with personalized ads. With FLoC, Google says, advertisers will retain the ability to deliver personalized promotions, but they’ll have access to far less data about users’ online activity. 

FLoC is delivered as a piece of software that runs in the user’s browser. It analyzes their online activity using machine learning and deduces what topics they’re interested in. Then, the user is added to a so-called “cohort” along with hundreds or thousands of other individuals who share the same interests. FLoC allows advertisers to target their ads at a cohort, but doesn’t provide them with data about the online activity of the individuals who make up the cohort, which Google says makes the technology more private than third-party cookies that do reveal this data.

The company is already testing FLoC in some installations of Chrome, which has a roughly 70% share of the browser market. But for the technology to become a standard part of the web, it will likely have to be supported by other browsers besides Chrome as well. That’s why the mixed reception from industry players such as Mozilla represents a significant development and, potentially, a setback for Google’s plans to make FLoC more widely available. 

Vivaldi, the company behind the browser of the same name, said on its blog that “we will not support the FLoC API and plan to disable it, no matter how it is implemented.” Brave stated that “FLoC materially harms user privacy, under the guise of being privacy-friendly” in a statement explaining why it won’t adopt the technology either.

Some organizations outside the browser ecosystem have joined the fray as well. Last month, the Electronic Frontier Foundation publicly argued that the technology will reduce online privacy.

Development of FLoC is still in an early phase, with Google having started the first user tests only last month. If widening adoption of the technology will require technical changes, the search giant may move to implement additional privacy features in FLoC besides the cohort-based mechanism for reducing advertisers’ access to user browsing data.

Image: Google