How do I know if a website is tracking me?

Every privacy signal, with the call behind it

2 signals, none of which ask your permission first. The entropy column is this site's own estimate of how much each signal narrows a crowd, not a measured population statistic; the methodology page explains why that distinction matters.

Why Do Not Track failed

The idea was sound: a header saying you would rather not be tracked, sent to every site, honoured voluntarily. The flaw was in the last word. Nothing obliged anyone to act on it, most of the industry did not, and a preference nobody enforces is a preference nobody has.

It then acquired a second problem. Because so few people turned it on, sending the header made a browser marginally more distinctive, which meant the anti-tracking signal was itself a tracking signal. Safari dropped it on exactly those grounds, Chrome removed the setting, and Firefox deprecated its own.

Its successor, Global Privacy Control, is a similar signal with actual legal weight behind it in some jurisdictions. That is the part that was missing the first time, and it is the reason to watch it rather than to write the idea off.

A fingerprint is not one thing anyone reads

There is no fingerprint API, and that is what makes fingerprinting hard to stop. A script reads a dozen ordinary properties it is entitled to read, one at a time, none of them alarming: user agent, screen size, timezone, language list, graphics renderer, how your device happens to draw text into a canvas.

Combining them is the whole trick. Each value on its own is shared by millions. The specific combination is shared by far fewer, and unlike a cookie there is nothing to delete. Clearing your storage, opening a private window and reinstalling your browser all leave your hardware exactly where it was.

This site computes that combination in your browser and shows you the parts. The result is never transmitted, hashed into an analytics event or written anywhere, because a site that explains fingerprinting while fingerprinting its readers would be worth nothing.

What a uniqueness score can and cannot tell you

An honest fingerprint estimate needs a population to compare against, and comparing means collecting. This site collects nothing, so it cannot claim to have measured how rare your combination is among real visitors, and it does not.

What it does instead is show you which signals your browser hands over, and attach a clearly labelled estimate of how much each one narrows a crowd. The estimates are this site's own, the method is written out on the methodology page, and the arithmetic assumes the signals are independent, which they are not. That assumption inflates the total, which is why the total is capped and the cap is explained.

For a measured comparison against a real population, EFF's Cover Your Tracks and AmIUnique both do exactly that, and both are linked from the fingerprint test. Using them means contributing your own fingerprint to their dataset, which is a fair trade and worth making knowingly.