Millions of Chrome users quietly added to Google’s FLoC pilot

Millions of Chrome users quietly added to Google’s FLoC pilot

Last month, Google began a test pilot of its Federated Learning of Cohorts—or FLoC—program, which the company has advertised as the newest, privacy-preserving alternative in Google Chrome to the infamous third-party cookie.

Sounds promising, right? Well, about that.

Despite Google’s rhetoric about maintaining user privacy, its FLoC trial leaves much to be desired. Google Chrome users had no choice in whether they were included in the FLoC trial, they received no individualized notification, and, currently, they have no option to specifically opt-out, instead having to block all third-party cookies on their Google Chrome browsers to leave the trial.

Electronic Frontier Foundation (EFF), which analyzed Google’s published materials and Chromium’s source code to better understand FLoC, lambasted the pilot program and the technology behind it.

“EFF has already written that FLoC is a terrible idea,” the digital rights organization said. “Google’s launch of this trial—without notice to the individuals who will be part of the test, much less their consent—is a concrete breach of user trust in service of a technology that should not exist.”

What is FLoC?

Labored acronyms aside, FLoC is part of Google’s broader plan to develop its idea of a more private web, as the search giant struggles with the death of the most important digital advertising tool in the history of the Internet—the third-party cookie.

We should be clear at the outset here. First-party cookies help the Internet function. Cookies help websites knit web page visits together. First-party cookies are used to knit together different visits to pages on the same website and help them remember useful information such as your settings, what’s in your shopping cart, and—most importantly—whether you are logged in or not.

Third-party cookies can also benefit Internet users, but for years, this technology primarily served as a sort of “tree of life” for the digital advertising economy, allowing advertisers to knit together web page visits from many different websites.

Implanted on millions of popular websites, tracking code that relies on third-party cookies has enabled the profiling of nearly every single Internet user by their age, gender, location, shopping interests, political affiliations, and religious beliefs. Third-party cookies also ushered in the era of “Real-Time Bidding,” in which businesses compete for the opportunity to deliver you ads based on those user profiles. And as online publishers like newspapers struggled to maintain in-print advertising revenue in their decade-long transition to digital, third-party cookies provided a sometimes necessary bargain for those publishers: Sell ad placements not to individual companies, but scale ad revenue rapidly by harnessing the results of mass user profiling.

Without the third-party cookie, much of this activity would either have been delayed or limited. So, too, would the money being made by the developers of those third-party cookies, which include many digital advertising companies and, as it just so happens, one notable Silicon Valley giant—Google.

The obvious question about FLoC technology then is: Why would Google create an alternative to the technology that helps them generate billions of dollars in ad revenue every year?

Because the third-party cookie is dying. As users increasingly protect their online privacy, they continue to install browser plug-ins that block the type of online tracking enabled by third-party cookies. Further, several browsers—including Safari and Mozilla—began blocking third-party cookies by default years ago.

If anything, FLoC is Google’s answer to a future that we all know is coming, in which the third-party cookie has lost its power.

Alright but what actually is FLoC?

How FLoC technology differs from third-party cookies is that, primarily, FLoC will create profiles on groups of users and not profiles on individual users. If FLoC becomes the norm, then Google Chrome users will have their activity tracked by Google Chrome itself. Based on that browsing activity—including what sites are visited and what searches are made—Google Chrome will then group users into “cohorts.” When you visit a website it will be able to ask your browser what cohorts you belong to and deliver ads that advertisers have targeted towards those “cohorts.”

This means that the broader digital advertising ecosystem will remain, but the wheels that churn to move it forward will undergo some changes.

In its FLoC announcement, Google explained that it is trying to find a balance between what it believes is the usefulness and the harm of third-party cookies.

“Keeping in mind the importance of ‘and,’ FLoC is a new approach to interest-based advertising that both improves privacy and gives publishers a tool they need for viable advertising business models,” the company said.

According to Google, FLoC technology will not share your individual browsing history with anyone or any company, including Google. Instead, that activity will be grouped into the activity of thousands of users in a cohort. Further, Google said that its Chrome browser will not create cohorts based on “sensitive topics.” So, that hopefully means that there will not be cohorts for people searching for aid in suicide prevention, domestic abuse, drug addiction, or private medical diagnoses, for example.

According to EFF, though, Google’s FLoC technology includes multiple privacy problems, such as the ability to use FLoC findings in conjunction with browser fingerprinting to reveal information about users, and the potentially never-ending quest to gather user data as a first-stage requirement only to then “unlearn” that user data if it could lead to the creation of a sensitive cohort.

The technical concerns with FLoC are many, but they’re difficult for the average user to grasp. What is easy to understand, however, is how those average users are left behind in Google’s FLoC trial.

A quiet trial

For such a seismic shift in the Internet’s infrastructure, many might assume that Google would announce the FLoC trial with more safeguards.

That’s not what happened.

In Google’s FLoC trial announcement, it gave Google Chrome users no option to opt out before the trial began. Instead, Google silently pushed FLoC technology to Chrome users in the US, Canada, Mexico, Australia, New Zealand, Brazil, India, Japan, Indonesia, and the Philippines. While Google described the trial as affecting a “small percentage of users,” according to EFF, that percentage could be as high as 5 percent.

That sounds small at first, but take into account that nearly-ancient estimates (circa 2016) put active Google Chrome users around 2 billion, meaning that the FLoC trial could affect up to 100 million people. That is an enormous number of people to subject to a data analysis experiment without their prior consent.

Google also said that users can opt-out of the FLoC trial by disabling third-party cookies through Google Chrome. It’s good that such an option exists, but it’s unfortunate that users will have to have some basic understanding of FLoC and third-party cookies to remove themselves from a trial that they might have no knowledge about.

Compounding the issue is that turning off all third-party cookies could remove a good deal of functionality from a user’s web experience. That seems both imprecise and unfair.

Finally, the FLoC trial affects more than browser users—it affects websites, too. Remember those publishers that Google said it would like to help? According to Google, “websites that don’t opt out will be included in the FLoC calculation if Chrome detects that they load ads-related resources”. Some of them have already opposed being automatically included into a technology trial that will result in the profiling of their readers—even if that profiling is supposedly less privacy-invasive.

Julia Angwin, editor-in-chief of the investigative news outlet The Markup, said that her organization chose to opt out of FLoC.

“We @themarkup opted out of Google’s newfangled cookie-less tracking system (FLoC) so our readers will not be targeted with ads based on visiting our site,” Angwin wrote on Twitter. “Others who care about reader privacy might want to do the same.”

Angwin is just one of many journalists who have reported on FLoC technology, most of whom have authored FAQs, explainers, and detailed guides on just what it is Google is trying to do with its recent experiment.

All of those explainers, in fact, point to the biggest problem here: Users are being included in something that they did not know about that will affect how they are treated on the Internet, and they had no say in the matter beforehand.

A private web can incorporate many things. At the very least, it should include user respect.


David Ruiz

Pro-privacy, pro-security writer. Former journalist turned advocate turned cybersecurity defender. Still a little bit of each. Failing book club member.