Except everything your browser handed over the moment this page loaded. No sign-up, no cookies, no permission prompts. Just ordinary JavaScript asking ordinary questions.
Sent with every request or readable by any script. Your language list and timezone alone narrow down where you are.
Screen size, CPU cores and graphics card are stable across sites, which makes them good tracking material.
Accessibility and privacy choices are exposed as CSS media queries and navigator flags. Opting out of tracking is itself a signal.
Every server you contact sees your IP address. This page never looks it up, but it can still read how fast and how you're connected.
Your device draws text and shapes in its own slightly unique way. Hash the pixels, add the installed fonts, and you get an ID that survives clearing cookies.
Recorded while you read. Session-replay tools log this, plus the exact path of your cursor, on many sites you visit.