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You do realise that responsive design is mainly done with CSS, right?

Yes. Upon reflection it's not that relevant to this discussion, but my point is that with just simple media queries, nefarious developers can use 1x1 tracking pixels (as background images, for example) to accomplish fingerprinting.

What exact method are you referring to with tracking pixels? I'm only aware of doing so based on the cache, which can be defeated by clearing the cache.

Loading pixels can be used to allow cross-site communication, but that's not really what's under discussion here (and FWIW doesn't run afoul of the security model I expect from a browser)

I recall reading about a scheme that puts a different 1x1 tracking pixel for every CSS pixel breakpoint, and then uses that as a piece of info in the fingerprint. I don't remember the details, I can't find it, and the tracker would still have to join on something (probably IP, which wouldn't work very well.)

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