Oliver Brotchie developed this CSS fingerprinting technique that requires no Javascript or Cookies to function and avoids anti-tracking methods such as NoScript, VPNs or browser extensions.

CSS Fingerprinting is a technique of tracking and gathering information on site visitors. This method exploits the nature of CSS to track various characteristics about the visitor’s browser and device, which can later be used to either identify or track said visitor.

Right now, at current spec, this method doesn’t scale, but with the next upcoming draft of the CSS specification, CSS Values 4, it will become far more scalable and precise.