FLoC is dead. Long live Google Topics API.

Don’t know what FLoC is? (OK, was.) Or what Google Topics API is about? You’re in good company: most people are in the same boat. But it’s relevant to you, and in fact to billions of people on this planet.


Right now, the biggest ad network on the planet is Google. Google targets ads to you by tracking you on the internet via both first and third-party cookies, but especially third-party cookies: tiny little bits of tracking code that tell Google where you go, what you do, what you buy, and more. Not everywhere you go, and not everything you do, and not everything you buy, but some large enough fraction of that to, with its first-party data on you from internet searches and Gmail usage and YouTube viewing habits and more, to know you pretty well.

Of course, that’s all web.

Google also owns Android, so if you use Android, Google knows what apps you download, has a pretty good idea what you buy in those apps, and much much more data thanks to your GAID/AAID (Google Ad ID or Android Ad ID) and the fact that many Android developers use Firebase for building and running Android apps.

So: the world is becoming more privacy-centric.

What will Google do?

Its new ad-targeting technology was FLoC: federating learning of crowds. That didn’t get great reception, mostly because it privileged Google as the recipient of somewhat-more-private data. Google’s answer to the failure of FLoC is Topics API: a way to target ads to you on any participating website based on your recent web activity … but privacy-safe. In-browser targeting. With noise added to the signal. And essentially decentralized.

So I went through the API and wrote about what I found

In short:

  1. Topics API is interest-based
  2. But Topics API is not very granular
  3. There could be public mapping of websites to topics
  4. There will be limited learning
  5. Plus, Google will introduce noise into the signal
  6. Targeting data will be repetitive
  7. Networks of sites won’t be super-effective at fingerprinting
  8. You can only learn what you already know (unless you’re an ad network)
  9. Big sites with lots of topics will suffer
  10. Google will decide what your site is about
  11. And, privacy is paramount

Check out the full story in my detailed explainer