Canvas fingerprint
A canvas fingerprint is a hash of how your browser draws hidden graphics; small rendering differences make it a stable device identifier.
What a canvas fingerprint is
The HTML canvas element lets a web page draw text and shapes with JavaScript. The result is not identical on every machine. Font rendering, anti-aliasing, sub-pixel positioning, the graphics driver, and the GPU all nudge individual pixels. A page can draw a fixed image off screen, read the pixels back, and hash them. The hash is the canvas fingerprint. It says nothing by itself, but it tends to be the same every time on your device and different on most other devices, which is exactly what a tracker wants.
Most implementations also render through WebGL, where the graphics card and driver leave an even stronger signature. Canvas and WebGL hashes are usually combined with other traits into a full browser fingerprint.
Why it matters
A canvas hash survives clearing cookies, private windows, and changing your IP address. For a site that wants to link sessions, it is far more durable than anything stored in the browser. For users of antidetect browsers the concern is the opposite: a spoofed canvas has to be stable within a profile and plausible for the claimed hardware. A hash that changes on every page load, or a Windows user agent drawing like a Linux server, is itself a detectable pattern.
How to check
Open the canvas fingerprint test. It draws the same reference image twice, shows you the picture, and reports the hash together with a stability check that reveals whether your browser adds random noise. The browser fingerprint page shows the canvas hash alongside the other signals so you can see the whole picture at once.
How to reduce it
- Firefox's fingerprinting protection returns a blank or noisy canvas to scripts that read pixels without user interaction.
- Browser extensions can add noise, but noise that changes per request makes you stand out as a protected user, which can be worse than a stable hash for sites that score consistency.
- Antidetect browsers replace the hash with a fixed value per profile. Check it with our test after creating a profile and again after updates, since both the browser and the spoofing can change.
A common misconception
Canvas fingerprinting does not require the canvas to be visible. The drawing is invisible and takes milliseconds; there is no indicator that it happened unless you use a tool that reports access to the API.