Browser fingerprint
A browser fingerprint is a set of traits about your device and browser that a site uses to recognise you, even if you cleared your cookies and signed out.
The point is the combination. Each trait on its own matches millions of people, but together — operating system, browser version, time zone, language, screen resolution, font set, video card, number of cores — they give a combination that can end up being one of a kind.
How it differs from cookies
A site places a cookie on you and can lose it: you clear it, the connection breaks. A fingerprint is read off your computer fresh, every time. It can't be cleared, because it isn't stored anywhere.
That's why two accounts in different windows of the same browser look like one person, no matter how much you clear cookies.
What it's made of
| What | Where it comes from |
|---|---|
| User-Agent, version, platform | the browser reports it itself |
| Time zone and language | system settings |
| Screen and window | pixel dimensions |
| Video card | the name, via WebGL |
| Cores, memory | the system reports it itself |
| Canvas, WebGL, fonts | a drawing and a list, unique to each machine |
| Network | the IP address and what's visible past the proxy |
What matters about spoofing
Consistency matters more than uniqueness. A fingerprint where the time zone is Moscow's, the language is Arabic and the IP is German is more suspicious than an ordinary one: real people don't come in that combination. We got burned on exactly this — the spoofing had to be redone so every value is derived from one source: the proxy's country.
Not everything is spoofed, and that's deliberate. The screen, for example, we deliberately leave alone: people freely move and resize the browser window, and a spoofed size will eventually drift from the real one — that's more noticeable than an honest value. The TLS fingerprint is also left genuine: ours comes from real Chrome, and there is no better cover than real Chrome.
How to check yours
Free and with nothing to install — the fingerprint check. It shows exactly what a site can see about you and highlights inconsistent values.