Browser Fingerprinting: How Sites Track You Without Cookies

Q: What is browser fingerprinting?

Browser fingerprinting is a tracking technique that collects attributes your browser reveals to every site, such as screen resolution, installed fonts, plugins, timezone, language, operating system, and GPU renderer, and combines them into a unique identifier. Unlike cookies, nothing is stored on your device, so clearing your browser data does not remove it.

Q: How does browser fingerprinting track you without cookies?

It identifies you by your device configuration rather than by stored data. The EFF found that 83.6% of browsers have a unique fingerprint, so a site can recognize you across visits even with cookies blocked. Techniques like canvas, WebGL, and AudioContext fingerprinting measure tiny hardware and OS differences to tell you apart from other users.

Q: How do I prevent browser fingerprinting?

Use the Tor Browser, which makes all users look identical, or extensions like CanvasBlocker that randomize fingerprint data. Avoid installing unusual fonts or plugins, stick to a common screen resolution, and disable JavaScript on sensitive sites. These steps reduce how unique your configuration looks, though they cannot make fingerprinting impossible.

Q: Can a VPN prevent browser fingerprinting?

No. A VPN hides your IP address, but your fingerprint is built from browser and device attributes a VPN never touches. In fact, combined with WebRTC and DNS leaks, fingerprinting can track you even behind a VPN, so you need fingerprint-specific defenses on top of one.

Q: Can I be tracked across websites with browser fingerprinting?

Yes. Advertising networks and analytics companies use fingerprinting as a fallback when cookies are blocked, following your activity from site to site. Fingerprints can change when you update your browser or OS, which makes long-term tracking less reliable, but in the short term it is highly effective.

~/sheets/browser-fingerprinting-explained.md

Cookies Are Not the Only Way You Are Tracked
You have probably heard of cookies. You might even clear them regularly. But there is a more insidious tracking method that does not store anything on your device: browser fingerprinting.
What Is a Browser Fingerprint?
A browser fingerprint is a collection of attributes your browser reveals to every website you visit. These include your screen resolution, installed fonts, browser plugins, timezone, language, operating system, GPU renderer, and dozens more data points. Combined, they create a unique identifier. Check your browser fingerprint now.
Why It Works
The Electronic Frontier Foundation found that 83.6% of browsers have a unique fingerprint. Even without cookies or login sessions, a website can identify you across visits with high accuracy. Your browser reveals enough information to distinguish you from millions of other users.
What Gets Collected
Common fingerprinting vectors include:
Canvas fingerprinting renders invisible text and measures pixel-level differences caused by your GPU and OS. WebGL fingerprinting queries your graphics hardware. AudioContext fingerprinting measures how your system processes audio signals. Even your battery level has been used for tracking on some platforms.
Who Uses It
Advertising networks use fingerprinting to track users who block cookies. Fraud detection services use it to identify suspicious logins. Some governments and law enforcement agencies use it for surveillance. Virtually any website can deploy fingerprinting scripts. Combined with WebRTC leaks and DNS leaks, fingerprinting makes it possible to track users even behind a VPN.
How to Reduce Your Fingerprint
Use the Tor Browser, which is designed to make all users look identical. Use browser extensions like CanvasBlocker to randomize fingerprint data. Avoid installing unusual fonts or plugins. Use a common screen resolution. Disable JavaScript on sensitive sites (though this breaks most of the web).
The Hard Truth
Browser fingerprinting is nearly impossible to fully defeat without significant usability trade-offs. The best approach is to minimize your unique attributes and use privacy-focused browsers. Start by understanding what your browser reveals with our fingerprint analysis tool.
Frequently Asked Questions
What is browser fingerprinting?
Browser fingerprinting is a tracking technique that collects attributes your browser reveals to every site, such as screen resolution, installed fonts, plugins, timezone, language, operating system, and GPU renderer, and combines them into a unique identifier. Unlike cookies, nothing is stored on your device, so clearing your browser data does not remove it. Check your own fingerprint.
How does browser fingerprinting track you without cookies?
It identifies you by your device configuration rather than by stored data. The EFF found that 83.6% of browsers have a unique fingerprint, so a site can recognize you across visits even with cookies blocked. Techniques like canvas, WebGL, and AudioContext fingerprinting measure tiny hardware and OS differences to tell you apart from other users.
How do I prevent browser fingerprinting?
Use the Tor Browser, which makes all users look identical, or extensions like CanvasBlocker that randomize fingerprint data. Avoid installing unusual fonts or plugins, stick to a common screen resolution, and disable JavaScript on sensitive sites. These steps reduce how unique your configuration looks, though they cannot make fingerprinting impossible.
Can a VPN prevent browser fingerprinting?
No. A VPN hides your IP address, but your fingerprint is built from browser and device attributes a VPN never touches. In fact, combined with WebRTC and DNS leaks, fingerprinting can track you even behind a VPN, so you need fingerprint-specific defenses on top of one.
Can I be tracked across websites with browser fingerprinting?
Yes. Advertising networks and analytics companies use fingerprinting as a fallback when cookies are blocked, following your activity from site to site. Fingerprints can change when you update your browser or OS, which makes long-term tracking less reliable, but in the short term it is highly effective.
Last updated: April 2026