Blocking cookies stops one method of following people between visits. It does nothing about the other one. Every page you open can read your screen size, your time zone, your languages, how many processors you have, which fonts are installed, and the tiny differences in how your particular graphics hardware draws a line. Put together, that is usually enough to pick you out of millions. This page collects exactly what any site could, shows you all of it, and keeps it here.
Collecting...
Each line is something any page can read without asking. The label on the right is a rough estimate of how much it narrows you down, in bits: ten bits is one person in a thousand, twenty is one in a million. The group totals do not add up to the number at the top, and are not meant to: many of these read the same underlying fact twice, so counting them all separately would say every browser on earth is unique.
This is the tracking that does not need permission. A cookie is stored on your machine, which means it can be refused, deleted and blocked, and that is why every site now asks. None of this is stored anywhere. It is read from your browser each time you arrive, put together into a number, and matched against the number from last time. Nothing to delete, nothing to refuse, no banner.
The unusual details are the identifying ones. Having a common screen size tells nobody anything. Having a rare one, plus an unusual time zone, plus a font that came with a program most people do not have, is the combination that leaves one person. That is why the estimate here is per line: the question is never how much a site knows but how few people share the answer.
An estimate is an estimate. The numbers here come from published measurements of how varied each detail is across the web, not from checking yours against a database, because there is no database here and nothing is uploaded. They are the right order of magnitude and they are not a measurement of you specifically.
Hiding is harder than it sounds. A browser that lies about itself is often more identifiable than one that does not, because almost nobody else is telling that particular lie. What works is being the same as many other people, which is why the browsers that resist this well do it by making everyone look alike rather than by making each person look random.
Nothing here leaves the tab. Everything on this page was read by script running in your browser and stayed there. That is the difference between this and the other sites that will show you the same thing: they keep what they collect, because collecting it is the business.
Yes, entirely. None of it uses cookies or storage of any kind. That is the point: refusing cookies does nothing about any of this, and a site that wants to follow you between visits does not need them.
A page draws some text and shapes onto an invisible canvas and reads back the exact pixels. The result depends on your graphics hardware, drivers, fonts and operating system, and is stable for you and different for most other people. It takes a few milliseconds and there is nothing to notice.
You can reduce it a great deal. A browser that blocks canvas and audio reading, reports a rounded window size and ships its own fonts removes most of what is on this page. Perfect is not available in a general-purpose browser, and a browser that tries too hard to be unusual becomes easy to recognise for exactly that reason.
It is the fingerprint of this browser as it is right now. Change something that feeds into it, such as a window size that is measured or a font you install, and it changes. Most of what feeds it does not change often, which is exactly why it works as an identifier.
Because seeing your own is the only way the argument lands. Reading a list of techniques is abstract; a page that tells you your own graphics card, your own font list and how many people share your screen size is not. It is read and shown, and it is never stored or sent.