Can someone give me an easy to understand example of what they are proposing? Assume that I don’t allow them to install any software/tool that helps them track me/my device.

I saw this comment and found it helpful but its still not clear to me

At its core, it establishes software components called “attesters” that decide whether your device and/or browser is “trustworthy” enough - as defined by the website you are trying to visit. Websites can enforce which “attesters” users must accept, simply by denying everybody access who refuses to bow down to this regime; or who uses attesters that are deemed “inappropriate”; or who is on a platform that does not provide any attesters the website finds “acceptable”.

In short: it is specifically designed to destroy the open web by denying you the right to use whatever browser you want to use, on whatever operating system. It is next-level “DRM”, introduced by affiliates of a company that already has monopolized the browser market. And the creators of this “proposal” absolutely know what they are attempting here.

Basically, it would allow websites to only serve users who comply with website requirements (i.e., no extensions, no ad blockers, only Chrome-based, whatever).

You (your browser) go to a website, example.com, which requires attestation. So you must go to an attestation server and attest your device/browser combo (by telling the attestation server whatever information it requires). If the attestation server thinks you are trustworthy, it gives you an integrity token that you pass to example.com, and then you can see example.com. The website knows which attestation server issued your integrity token, so you can’t create your own.

So no extra software means no attestation server would attest you; means you can’t see example.com. End of story. It’s the same as the current “your browser is not supported” window, only you can’t get around it by changing the user agent.

As usual with these initiatives, bullshit is spread across different specs - this spec by itself implies that any number of attestation servers can exist, and they can check whatever they want, and no browser should be excluded, etc., etc., but practical implementation would probably check installed extensions, etc.

Wouldn’t spoofing work? Like, if the browser just sends “yes, no extensions, adblock, blah blah” then how would the attestation server know if that’s true? Or does it require signed binaries, or some special hardware?

Depends on if they used cryptographic signatures. Those would be impossible to spoof because any change in the client would change the hash completely.

Google silently shipping signed chrome executables soon…

And then people wonder why non chromium browsers are important

Chromium is cancer.