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Wait, WTF happened with Google FLoC? We explain

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By Kendra Clark | Senior Reporter

January 25, 2022 | 9 min read

Out with the old, in with Topics, says Google. The tech giant has announced that it’s scrapping its Federated Learning of Cohorts (FLoC) scheme – its original cookie replacement plan. In its place is a new proposal for privacy-focused ad targeting: Topics. Here’s what you need to know about how Topics works, and why FLoC flopped.

Google today announced it is pulling the plug on its Federated Learning of Cohorts (FLoC) project. FLoC was created to replace third-party cookies (which track individual users’ behavior across the web) by grouping users into ‘cohorts’ in accordance with their interests. In lieu of FLoC, which in its short life was the subject of intense debate among both privacy advocates and tracking apologists, the tech titan has introduced Topics.

Topics, like FLoC, still serves as an alternative to third-party cookies but takes a relatively different approach. Instead of lumping users together, Topics enables a user’s browser to learn about them on an individual level based on their browsing behaviors. As a user moves across the web, Chrome will record information about the sites they have visited for the previous three weeks and store it. Topics will then assign a user specific interests – beginning with a pool of just 300 possible ‘topics’ – according to their browsing behavior. Think ‘fitness,’ ‘travel’ or ‘fashion.’ These topics, according to Google, marry company’s proprietary taxonomy with the Interactive Advertising Bureau’s Content Taxonomy V2. For sites that Google has yet to categorize, basic machine learning algorithms will assess the site’s domain name and make an estimate.

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Sheep sticking its tongue out

Google’s FLoC was a flop

When a user reaches a site that supports Topics for ad purposes, the browser will pull three topics that the user is interested in from the past three weeks – chosen at random from the user’s top five topics each week – and allow the website to share these topics with advertisers. This information will be used to help advertisers determine which ads to display, without allowing access to granular user data or identifiers.

Graph representing Google Topics versus third-party cookies

Such radical experimentation is intentional, Vinay Goel, product director of Privacy Sandbox at Chrome, tells The Drum. “We purposely wanted to design The Privacy Sandbox within public forums so that we can collaborate and iterate on the technologies to make sure it can work for all parties. As a part of that process, we expected to hear feedback on ways to improve the technologies. That is exactly what happened here – we heard feedback about how to improve on our original design, and we’ve incorporated that feedback into the new Topics API. And with the Topics API, we are seeking feedback from interested parties, and will actively explore how to incorporate that feedback into the design of Topics.”

But what was the issue with FLoC?

While there were surely a multitude of factors influencing Google’s decision to sunset FLoC, among the most pressing is likely to have been growing concerns that the framework didn’t do enough to inhibit fingerprinting. The Electronic Frontier Foundation, a San Francisco-based nonprofit focused on protecting consumers’ digital rights, for one, has suggested that with so many granular categories in FLoC, it would be possible to employ fingerprinting techniques to identify individual users within a cohort and ultimately assign unique identifiers to those users.

With Topics, a user can only be assigned topics from a pool of 300 total options, making it far more difficult to potentially identify individual users associated with a given topic. Plus, with five topics assigned per user per week – instead of one FLoC cohort – it will be “difficult for two sites to use topics to re-identify a user, since there would only be a 20% chance at most that two sites could receive the same topic for the user in a given week,” says Chrome’s Goel.

He argues that the model further hampers fingerprinting by restricting the ability of sites to gain information about users through second or third parties. “Each site or embedded service requesting Topics information would receive a topic for the user based on browsing history on sites where that party was present. This model limits the availability of directly-observed activity.”

Fingerprinting aside, another key problem with FLoC is what Ari Paparo, head of partnerships and strategy at Comcast’s TV and premium video ad platform FreeWheel, calls “the moral problem.” In essence, with FLoC, the browser collects user data and shares it broadly without explicit consent from users. “From a certain perspective you could argue this is actually worse for privacy than cookies,” Paparo tells The Drum. He worries that the Topics API suffers the same shortcoming. Google, for its part, has said that it plans to implement controls for users that will allow them to view the topics that they have been assigned, remove specific topics or disable the Topics API altogether.

In a similar vein, FLoC has been criticized for its infrastructural potential for discrimination. Cohorts could include sensitive demographic data, creating the possibility for discriminatory ad targeting. This time around, Google has said that topics have been created to exclude potentially sensitive information such as race, gender or religion.

Aside from these considerations, Paparo acknowledges that some of the controversy surrounding FLoC could very well have just been an optics problem. Because the framework was difficult to understand, it seemed inherently “more sinister.”

On the other hand, the idea that the browser is simply sharing three generic topics about a given user – as is the case with Topics – appears to be a relatively harmless approach in comparison. It’s also worth noting that through FLoC, a user was assigned to new cohorts each week based on their browsing habits from the previous week, whereas Topics assigns topics weekly but holds on to those topics for three weeks.

And how will advertisers fare?

It’s clear that Topics includes new protections that are likely to better obfuscate user identity and mitigate the potential for abuses. And while Google claims it offers developers and advertisers greater transparency into user interests, ad industry players contend that Topics will provide few if any granular insights about a user that would enable effective personalization.

“With FLoC, advertisers and advertising parties had to make their own interpretations of what a website visitor grouped within a particular cohort may be interested in. That left room for interpretation, including possibly misinterpreting the website visitor’s interests,” says Goel. “We believe providing Topics instead of cohorts provides clearer insight into what advertising categories the website visitor may be interested in.”

Some ad industry leaders, however, call bullshit. “The only benefit this has for advertisers is that it is slightly better than nothing,” says Wayne Blodwell, founder and chief executive officer at The Programmatic Advisory. “For some of the large brand advertisers who want to reach broad audiences, this is something, but for the majority this has no value whatsoever as the category is too broad for their targeting criteria or campaign budgets.”

Today’s announcement is sure to help Google divert attention away from a smattering of recent press scandals. Earlier this week, the District of Columbia and three other states levied a lawsuit against the tech giant, alleging that it has been practicing deceitful location data tracking. This is an especially damning accusation considering the company’s highly-publicized efforts to introduce what it has billed as privacy-centric tech and advertising solutions in recent years like FLoC and now Topics. The news came just as a group of German publishers – including industry heavyweight Axel Springer – filed a complaint arguing that Google’s plan to eliminate third-party cookies not only unfairly impedes their abilities to target advertisements effectively but also violates EU law.

Farhad Divecha, founder of London-based digital marketing agency AccuraCast, says that Google has been “indecisive” regarding its stance on privacy compared to competitors like Meta, which in 2020 rolled out its Conversions API and has since “steadfastly supported it.” In any case, it’s clear that Google’s privacy posture is under fire from all sides.

“Topics might be seen as a way to keep the wolf from the door,” says Blodwell, “but that door will be knocked down again soon.”

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