What is browser fingerprinting?
Cookies are not the only way websites recognize you. Browser fingerprinting builds a near-unique ID from dozens of small details your browser reveals — and it works even in incognito mode.
The short version
Every time you open a page, your browser quietly exposes dozens of technical details: your screen size, timezone, language, graphics card, installed fonts, and more. On their own, each detail is harmless. Combined, they form a pattern that is often unique to your exact device — a fingerprint.
Unlike a cookie, a fingerprint is not stored on your machine, so you can't simply delete it. Clearing cookies or going incognito does not reset it.
What signals make up a fingerprint
A typical fingerprint is assembled from signals like these:
- Canvas & WebGL — how your GPU renders text and graphics, often the most distinctive signals.
- Fonts — the exact set of fonts installed on your system.
- Screen & hardware — resolution, pixel ratio, CPU cores, memory.
- Locale — timezone and language preferences.
- Audio — how your audio stack processes a test tone.
- User agent — the browser and OS you report.
Why websites fingerprint you
Three main reasons. Advertisers and analytics use it to track you across sites without cookies. Fraud and risk systems use it to spot bots, fake signups, and stolen accounts. And account-security systems use it to notice when a login looks like it came from an unfamiliar device.
That last reason is why fingerprinting matters far beyond privacy: if your environment looks inconsistent or unnatural, platforms may flag a login, demand extra verification, or restrict the account.
Fingerprinting vs cookies
Cookies are a file the site asks your browser to store; you can see and delete them. A fingerprint is inferred from how your browser behaves, so there is nothing to delete. The practical defense is not erasing it — it's looking less unique, and looking consistent.