News has been moving fast about Google’s FLoC system. If you don’t know what it is, look at where it’s coming from and you can probably guess. Last Thursday blog posts were recommending the addition of this line to your web server software, which I did:

Permissions-Policy: interest-cohort=()

Rohan Kumar elaborated that while this is technically correct, it’s not always necessary, nor the best way to do it:

If your website does not include JS that calls document.interestCohort(), it will not leverage Google’s FLoC. Explicitly opting out will not change this.

He recommends not using third-party scripts, and implementing a Content Security Policy header to block execution. I’ve been doing this for years; it’s good advice in general.