Browser fingerprinting is a way to recognize a browser by the details it shares with every website: its version, operating system, screen size, fonts, graphics card and dozens of other values. Each detail is common, but the combination is often unique, so trackers can follow you across sites and visits without cookies.
See your own fingerprint with our Browser Fingerprint test.
What goes into a fingerprint
| Signal | How it is read |
|---|---|
| User agent | Browser name, version and operating system, sent with every request |
| Screen and window size, pixel ratio | JavaScript screen and window properties |
| Language and timezone | Browser settings and the system clock |
| Hardware | Number of CPU cores, approximate memory, touch support |
| Graphics | WebGL reports the GPU vendor and model |
| Canvas | The browser draws hidden text and shapes; tiny rendering differences produce a unique hash |
| Audio | Processing a silent audio signal produces device-specific results |
| Fonts | Which fonts are installed |
| Network | Your IP address and, without protection, WebRTC addresses |
How fingerprinting is used
- Advertising and analytics: recognizing returning visitors who block or delete cookies.
- Fraud prevention: banks and shops spot logins from a new device or many accounts from one device.
- Bot detection: automated browsers have telltale fingerprints.
The same technique that protects your bank account also lets ad networks build a profile of you.
Why cookies and private mode are not enough
Clearing cookies or using a private window removes stored identifiers, but your fingerprint stays the same because it is built from your device and settings, not from stored data.
How to protect yourself
- Use a browser with fingerprinting protection. Tor Browser makes all users look the same. Brave randomizes several values. Firefox blocks known fingerprinting scripts and, with resistFingerprinting enabled, standardizes many values. Safari reduces the data it exposes.
- Blend in. Common screen sizes, default fonts and few extensions make you less unique. Every unusual extension or setting adds bits of identifying information.
- Keep your browser updated so you share a version with millions of others.
- Block trackers with a reputable content blocker.
- Hide your IP with a VPN, since the IP is usually combined with the fingerprint.
Is fingerprinting legal?
Under the EU's ePrivacy rules and the GDPR, fingerprinting for tracking needs the user's consent, just like cookies. Regulators in the UK have said the same. In many other countries it is less regulated.
Frequently asked questions
Can I make my fingerprint completely unique-proof?
Not completely, but Tor Browser comes closest by making all its users report the same values.
Does a VPN stop fingerprinting?
No. A VPN changes your IP address, not your browser's characteristics.
Does my fingerprint change?
Yes, with browser updates, new fonts or extensions and a different screen. Trackers use statistical matching to follow those changes.