There’s like a billion side channels to determine how big the screen is unless you just want to entirely break basic css. Which is a pretty unreasonable way to address this problem.
Surprisingly, most sites are perfectly usable with CSS disabled. They end up looking a bit like "motherfucking website"[1], or what you see in a text-based web browser.
Wouldn't loading all external links right away (think background-image) solve this? How does the site exfiltrate the gathered information without javascript or tracking pixels?
Edit: Having a bunch of html buttons/links, showing a different to agents based on their resolution and waiting to see which ones they follow would break this, unless everyone crawls a lot of stuff they don't need. Pretending to be one of a few common sizes is probably a better solution.
How? Admittedly my knowledge of CSS is dated, but without scripting enabled you can't set cookies, make auto server request, or even auto set an external CSS file (that could be served and counted)..
Its not something I've considered before and i am genuinely curious how this would work.
You can make server requests by loading images and fonts. Browsers only load those resources they actually need, so there's lots of opportunities for conditionally triggering requests. Media queries for window size, fallback fonts to check installed fonts, css feature checks to make guesses at the browser type, ...
