[ithkuil]

What stops a browser implementing the API but feeding made up information through it?

[Groxx]

Nothing.

Until Web Environment Integrity lands too.

(afaik there's no FloC attestation, but I'm not 100% confident about that)

[janc_]

unfortunately, both blocking the API, or faking it, will be abused to track users, unless a significant number of users do it in the same way...

[ithkuil]

Because a tracker could detect that your topic of interest are fake? How would they know?

[majormajor]

If they're relatively unique they can just track you across sites and use your browsing history instead.

[janc_]

Depends, but either the topics never changing, or them changing too randomly, could all be detected when combined with other tracking, and become part of your identity as such...

[sltkr]

Simple. If the Topics API is disabled, then you are a nerd who spends too much time on sites like Hacker News, and they can show you ads accordingly.

[peddling-brink]

I imagine a browser extension could do that.