What this page just learned about you

Collecting...

Everything it collected

Each line is something any page can read without asking. The bits figure estimates how much it narrows you down.

What actually helps

How it works

What makes you identifiable is not any single thing

None of the values on this page is secret and none of them is unusual on its own. Plenty of people use the same browser version; plenty share your screen size; plenty are in your time zone. What identifies a browser is the combination, and combinations get rare very quickly: a handful of ordinary facts multiplied together is frequently unique across the whole web.

The usual measure is entropy in bits: each bit halves the number of people you could be. Around 33 bits would single out one person on earth, and an ordinary browser gives up a good deal more than that once fonts and graphics rendering are included.

Where it comes from

Sent before any script runs. Your IP address, the user agent, the languages you accept, and what compression and media formats you support. These arrive with the request itself.
Read by a line of JavaScript. Screen size and colour depth, device pixel ratio, time zone, processor count, memory, whether you have a touch screen.
Measured rather than asked for. The distinctive one. Drawing the same shape or the same text and reading the pixels back gives a value that depends on your graphics hardware, its driver and your font rendering: the canvas and WebGL fingerprints. Nothing is stored on your device and nothing needs your permission.
The list of fonts you have installed, which is a portrait of the software you have installed.

Why this cannot be fixed by deleting anything

There is nothing to delete. A cookie is a file you were given and can throw away; a fingerprint is measured fresh each time from what your machine is. Clearing storage, using a private window and refusing cookies all leave it untouched, which is exactly why the technique became popular as cookie rules tightened.

What actually helps is being less distinctive rather than more protected: Tor Browser makes everyone look the same, which is a different and better strategy than making yourself unusual. Counter-intuitively, a rare set of privacy extensions can make you easier to recognise rather than harder. What a website learns before you click goes through the trade properly, and COOKIEAUDIT covers the part that is a file you can delete.

Everything here is collected and shown in your own browser and kept nowhere. This page is a demonstration of what any site could take, not a site taking it.

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