But apart from this, the canvas can be used as additional entropy in the web browser's fingerprinting and used for online tracking purposes.
The technique is based on the fact that the same canvas image may be rendered differently on different computers. This happens for several reasons. At the image format level – web browsers use different image processing engines, image export options, compression level, the final images may get different checksum even if they are pixel-identical. At the system level – operating systems have different fonts, they use different algorithms and settings for anti-aliasing and sub-pixel rendering.
Below you can see if the Canvas is supported in your web browser and check whether this technique can keep track of you. In addition, a little continuing research will show how really unique and persistent Canvas Fingerprint in real life, and whether your signature in the BrowserLeaks database (nothing is collected right here!).