A Canvas fingerprint is a summary of a drawing produced through the browser's graphics APIs. It is useful for comparing observations made with the same drawing and method. A hash by itself does not tell you how many other people share that result, whether a tracker can recognize you, or whether your browser is safe.
Open the browser fingerprint check and find the Canvas result. This guide describes the current BrowserCheck method; it does not present measurements from a population of browsers.
What this check draws
BrowserCheck creates a 200 by 60 pixel canvas, selects 14px Arial, paints an orange rectangle and draws “BrowserCheck” twice with different colors and positions. It then calls toDataURL and computes a short hash of the exported image representation. The source is getCanvasHash in src/hooks/use-extended-fingerprint.ts.
That method matters. Another test may draw different text, use another font or canvas size, or hash raw pixels instead of an encoded image. Its output is not directly comparable to this one. Even here, a short hash is a convenient summary with possible collisions, not proof that two underlying images are identical.
Canvas also supports ordinary graphics, charts and image editing. The presence of a working drawing API does not establish that a website is tracking visitors. The privacy question involves what a site collects, combines, retains and shares.
A repeatable comparison
- Record the browser and version, operating system, profile, extensions and relevant privacy setting. Keep the record locally; there is no need to publish the hash.
- Load the same BrowserCheck URL and wait for a completed result. Record unavailable states separately from hashes.
- Repeat without changing the environment. This checks stability in that session, rather than assuming it.
- Change one setting, then run the same page again. If the setting requires a browser restart, restart before measuring.
- Restore the setting and repeat once more. Note any browser or operating-system update that occurred during the exercise.
Avoid changing a privacy setting, several extensions and the browser version simultaneously. You would observe a difference without being able to attribute it to one cause. A private window is a separate test condition, not an automatic clean control: its extension permissions and browser policies may differ.
Reading the result
| Observation | Supported conclusion | What it does not prove |
|---|---|---|
| Same hash on repeated runs | This method returned the same summary | Global uniqueness, complete stability or anonymity |
| Different hash after one change | The observations differ | Which internal rendering component caused it |
| Hash changes without an intentional change | The observed output is not stable in this sequence | That a particular privacy defense is active |
| Unavailable or unsupported | This run did not obtain a usable value | That all fingerprinting is blocked |
If the result is unavailable, first repeat with the same settings. Then check whether the page reported an error or the browser blocks canvas readback. Do not interpret missing data as a successful privacy test. If you temporarily change a protection for diagnosis, restore it when finished.
Why a hash is not a privacy score
BrowserCheck does not compare your Canvas hash against a representative database of people. It cannot calculate your uniqueness or the probability that another site can identify you. Two sessions sharing one Canvas result can differ in language, screen, fonts, graphics information or network context. A changed Canvas result also says nothing about cookies that remain in a profile.
For a broader explanation, read how browser fingerprinting works and the WebGL test guide. Keep Canvas rendering, WebGL information and network checks as separate observations before drawing a conclusion.
Sources and review notes
This guide was checked against BrowserCheck's implementation and the references below on September 27, 2026. It contains a comparison procedure, not a claim that particular browser releases have been tested.
- MDN: HTMLCanvasElement.toDataURL documents image export and failure conditions.
- HTML specification: Canvas defines the drawing and serialization APIs.
- W3C: Mitigating Browser Fingerprinting discusses the broader identification risk from combining observable properties.