So after thinking a lot about FLOC and how it impacts and changes the advertisement environment, I have more questions than answers.

And at least from my current understanding, it becomes worse for organisations that want to advertise, which might includes your government trying to educate citizens about things, while not really making things much better for individual privacy, due to the ability to correlate cohort IDs to identify users.

Mhm ._.

While a lot of people decided to set a header to opt-out from FLOC tracking for their users, I decided to embrace it and let people make up their own mind.

For those interested in the banner, here are the implementation details:

It's kept simple and efficient. It'll only show up, when your browser implements the API. Enjoy!

I just realised that implicitly I built a FLOC tester :D

Want to check if your browser implements FLOC? Just go to and if a banner shows up warning you about FLOC, your browser is affected. Amazing!

Related: if you want to test if the detection works, you can use the following command in (Fedora) Linux with :

`chromium-browser "--user-data-dir=$(mktemp -d)" --enable-blink-features=InterestCohortAPI --enable-features="FederatedLearningOfCohorts:update_interval/10s/minimum_history_domain_size_required/1,FlocIdSortingLshBasedComputation,InterestCohortFeaturePolicy"

(It'll enable the feature in a temporary profile that is used until you terminate the command)

And it's done! A 💯% legitimate implementation of Google's FLoC standard for Firefox in an extension:

Finally we can have this awesome private ad company gift in a browser that is not chromium based!

And of course it's a completely serious and not at all satirical/sarcastic implementation. I swear!

Whoops, the repository wasn't set to public yet. That's fixed now!


Oh no! I'm so floced!

Needed to set my User-Agent to chromium for the scanner test to actually try it, but here we go. My extension works! And the best part, I'm in a new cohort on every page reload.

Finally I can use FLoC in Firefox! 🤡

GitHub Pages "blocks" Google's FLoC now by adding the opt-out header.

I don't think this is any reason to celebrate. pulled two tricks here:

1. It identified all websites that are against this standard, making it easy to rank them worse.
2. Provided a technical solution to a social problem making all the tech elitist feel good by adding a header instead of protesting.

All in all, I feel this header legitimises the standard more and more "because you can opt-out".


By the way, I wrote a little article on my blog how Google's FLoC incentivises more tracking, not less.

TL;DR: Cohorts are supposed to be meaningless and rely on first-party tracking to "make sense out of them" in order to continue existing business practice's of targeted advertisement. Resulting on harder-to-block tracking for all users and with strong disadvantages for advertisers competing with Google.

@doenietzomoeilijk I honestly believe they didn't, but obviously they don't mind. It's business after all and more money is more money.

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