Canvas Fingerprint Viewer
See the canvas fingerprint your browser hands to any site that asks.
How this test works
The same drawing instructions produce subtly different pixels on different machines. Font rasterisation, anti-aliasing, sub-pixel positioning and GPU compositing all vary by operating system, driver and hardware, so an identical canvas hashes differently across devices while staying stable on any one of them. That is what makes it useful for tracking without cookies: no storage is involved, so clearing your browser data changes nothing. This page draws such a canvas, hashes the result, shows you the value and throws it away. It does not tell you how unusual your value is, because that would require a database of other people's fingerprints.
What the results mean
- Canvas hash
- A short digest of the rendered image. Stable for you, different for most other machines.
- Unavailable
- The browser refused the read. Firefox in strict mode and the Tor Browser both do this, and it is a real reduction in exposure.
- How rare is this?
- Not measured, deliberately. Answering it would mean collecting what this page exists to warn you about.
- Value transmitted
- No. Computed in the page, displayed, discarded.
Common problems and fixes
- My hash changes every time I reload
- An extension is randomising canvas output. That defeats simple matching but is itself detectable, and a browser that randomises consistently stands out from one that does not.
- It says unavailable
- Your browser is blocking canvas reads, which is the strongest outcome here. Firefox strict mode and the Tor Browser both do it.
- Two of my devices show the same hash
- Unusual but possible on identical hardware with identical software. Canvas is one signal among many rather than a unique identifier on its own.
Frequently asked questions
What is canvas fingerprinting?
Drawing an image with JavaScript and reading back the pixels. Because rendering differs slightly by operating system, GPU and driver, the result identifies a machine without storing anything — which is why clearing cookies has no effect on it.
Why will this page not tell me how unique I am?
Because that requires comparing you against a population, and building that population means storing fingerprints from every visitor. Sites that quote you a uniqueness figure collected the data to do it.
How do I stop canvas fingerprinting?
Use a browser that blocks it — Firefox in strict mode, or the Tor Browser. Noise-adding extensions are worse than they look: a browser that returns a different value every time is itself a distinctive signal.