What is browser fingerprinting?
Browser fingerprinting identifies you without cookies. A script reads dozens of harmless-looking details (your screen size, time zone, languages, installed fonts, graphics card and how your browser draws text) and combines them into a single identifier. Each detail is shared by many people, but the combination is often rare enough to recognise one browser among millions.
Unlike a cookie, you cannot delete a fingerprint, and it persists across private windows and, partly, across browsers on the same device. That is why advertisers and fraud-detection services use it. Read our explainer on what browser fingerprinting is.
What this test measures
- Basic attributes: user agent, languages, time zone, screen, colour depth, CPU cores, device memory, touch support.
- Fonts: which of 46 common fonts are installed. The set of fonts varies a lot between devices.
- Canvas: we draw text and shapes and hash the pixels. Tiny differences in graphics hardware and software make this value surprisingly distinctive.
- WebGL: the graphics card vendor and model your browser reports.
We also draw the canvas twice. If the results differ, your browser is adding random noise to defeat fingerprinting, which is exactly what Brave and Firefox's strict mode do.
How to read the "bits" number
Each attribute gets a rough estimate of the information it carries, measured in bits. Every bit halves the group of people you could be. About 33 bits is enough to single out one person among eight billion. Our numbers are illustrative estimates from published research, not measurements against a live population, and adding them assumes independence, which overstates uniqueness a little. Use the figure to compare setups and see which details you give away, not as a precise probability.
How to reduce your fingerprint
- Blend in. Tor Browser makes every user look the same. That is the strongest approach.
- Use a browser with built-in protection. Brave randomises canvas and audio output. Firefox can enable "resistFingerprinting".
- Avoid unusual customisation. Rare fonts, exotic extensions and unusual screen sizes make you stand out.
- Keep your browser updated. Browsers keep trimming the data they expose, for example by shortening the user agent.
Be wary of extensions that "spoof" values. A mismatch between what you claim and how your browser behaves can make you more distinctive.
Canvas, WebGL and font fingerprinting
The three most distinctive signals are drawn rather than read. Canvas fingerprinting asks the browser to render hidden text and shapes, then hashes the pixels, which differ slightly by graphics driver, operating system and font rendering. WebGL exposes the graphics card model. Font detection measures how wide text is in each font to learn which are installed. See canvas fingerprinting explained for the mechanics.
Which browsers resist fingerprinting?
Tor Browser makes all users look alike. Brave adds small random changes ("farbling") to canvas, audio and some hardware values. Firefox offers strict tracking protection and an optional resist-fingerprinting mode, and Safari limits several signals by default. Chrome and Edge expose the most. Run this test in each browser you use and compare the bits figure. Our step-by-step guide on how to prevent browser fingerprinting covers settings and trade-offs.
Last reviewed 2026-10-26. Found a mistake? Report a correction (how we handle them).