Home Privacy FLoC Origin Trials Kick Off In The United States And Other Regions

FLoC Origin Trials Kick Off In The United States And Other Regions

SHARE:
Let the FLoC testing begin (but not in Europe, yet).

Let the FLoC testing begin (but not in Europe, yet).

On Tuesday, Chrome started rolling out initial origin testing of its Federated Learning of Cohorts (FLoC) proposal with a small percentage of users in the United States and across Australia, Brazil, Canada, Indonesia, Japan, Mexico, New Zealand and Philippines.

“FLoC is still in development and we expect it to evolve based on input from the web community and learnings from this initial trial,” Marshall Vale, a Chrome product manager, wrote in a blog post announcing the start of testing.

Origin trials are a way for developers to test experimental web features and gather early feedback on usability, effectiveness and functionality before those features are made available either for more extensive testing or for general use.

FLoC, which uses on-device machine learning to create cohorts for targeting based on browsing patterns, is how Google will enable interest-based advertising on the web after the end of third-party cookies.

FLoC is also one of the most hotly debated proposals currently being kicked around in the Chrome Privacy Sandbox.


Ruffled feathers

There was quite a stir last week after Google engineer Michael Kleber, told members of the Improving Web Advertising Business Group (IWABG) at the World Wide Web Consortium that FLoC origin trials would not be turned on in Europe as part of the initial testing phase.

Many interpreted Kleber’s statements as acknowledging that FLoCs might not be comparable with the EU’s General Data Protection Regulation (GDPR), including a question as to who acts at the data controller as defined under GDPR in the creation of a FLoC ID.

Vale followed up a few hours after the IWABG meeting with a series of tweets asserting that Chrome’s plan is to “begin testing in Europe as soon as possible” and that Google and Chrome are “100% committed to the Privacy Sandbox in Europe.”

But Europe might not be 100% committed to the Privacy Sandbox.

In January, in response to complaints, the Competition and Markets Authority (CMA), the UK’s antitrust regulator, launched an investigation into the Privacy Sandbox to assess whether the proposals within could cause ad spend to become even more concentrated within Google’s ecosystem at the expense of its competitors.

Subscribe

AdExchanger Daily

Get our editors’ roundup delivered to your inbox every weekday.

Better than cookies?

Another concern is whether FLoCs both create new, and worsen existing problems, in trying to solve the privacy-related challenges associated with third-party cookies and cross-site tracking.

An excoriating post from the Electronic Frontier Foundation (EFF) in early March with the headline “Google’s FLoC Is a Terrible Idea” argues that FLoCs could exacerbate “many of the worst non-privacy problems with behavioral ads, including discrimination and predatory targeting.”

Google is now publicly defending the FLoC proposal.

In his post, Vale makes the case for FLoCs, which he says will allow people to remain anonymous as they browse sites because cohorts are defined by similarities in browsing behavior and not based on who someone is as an individual. FLoCs will contain “thousands of other people who have similar browsing histories,” he wrote.

Vale also said that unlike third-party cookies, a user’s browsing history will not be shared with “Google or anyone” and that “everyone in the ads ecosystem, including Google’s own advertising products, will have the same access to FLoC.”

Lastly, Vale claims that Chrome “won’t create groups that it deems sensitive” and that before a cohort becomes eligible for use, Chrome will analyze it to see if the cohort is regularly visiting pages associated with sensitive topics, such as medical, religious or political sites. If so, Chrome won’t use that cohort.

This argument is unlikely to convince critics, though. The EFF, for example, emphasized in its post that platforms are often unable to prevent the abuse of their technology even with the best of intentions, and that there’s no guarantee the unsupervised algorithm that underlies FLoC won’t group users based on sensitive characteristics, such as substance abuse or financial hardship.

Regardless, it will be possible for people to tell FLoCs to … well, FLoC off (sorry, irresistible).

Starting in April, Chrome will introduce a control within the browser settings that people can use to opt out of being included in FLoC and other Privacy Sandbox proposals. Until then, anyone that’s chosen to block third-party cookies will not be included in the FLoC origin trials.

Speaking of the origin trials, although there is no official timeline as to when FLoC testing will begin in Europe other than “as soon as possible,” Google confirmed with AdExchanger that advertiser testing of FLoCs within Google Ads is still slated to begin in Q2.

Must Read

The Big Story: Live From CES 2026

Agents, streamers and robots, oh my! Live from the C-Space campus at the Aria Casino in Las Vegas, our team breaks down the most interesting ad tech trends we saw at CES this year.

Monopoly Man looks on at the DOJ vs. Google ad tech antitrust trial (comic).

2025: The Year Google Lost In Court And Won Anyway

From afar, it looks like Google had a rough year in antitrust court. But zoom in a bit and it becomes clear that the past year went about as well as Google could have hoped for.

Why 2025 Marked The End Of The Data Clean Room Era

A few years ago, “data clean rooms” were all the ad tech trades could talk about. Fast-forward to 2026, and maybe advertisers don’t need to know what a data clean room is after all.

Privacy! Commerce! Connected TV! Read all about it. Subscribe to AdExchanger Newsletters

The AI Search Reckoning Is Dismantling Open Web Traffic – And Publishers May Never Recover

Publishers have been losing 20%, 30% and in some cases even as much as 90% of their traffic and revenue over the past year due to the rise of zero-click AI search.

No Waiting for May – CES Is Where The TV Upfront Season Starts 

If any single event can be considered the jumping-off point for TV upfronts, it’s the Consumer Electronics Showcase (CES), which kicks off this week in Las Vegas, Nevada.

Comic: This Is Our Year

Comic: This Is Our Year

It’s been 15 years since this comic first ran in January 2011, and there’s something both quaint and timeless about it. Here’s to more (and more) transparency in 2026, and happy New Year!