How to disable use of HTML5 canvas image data?

After login to discourse forums, Tor Browser will show:

Will you allow to use your HTML5 canvas image data? This may be used to uniquely identify your computer.

How to disable use of HTML5 canvas image data?

Does it show that on all Discourses? For example

No, I could not reproduce on

Then maybe the Discourse(s) you tried is doing some fingerprinting?

We aren’t by default in Discourse. Unless they’ve installed the discourse-fingerprinting plugin (or they did it manually in a theme).


Very strange. I am the admin of it and I didn’t add anything even remotely related to HTML5 canvas. (And I guess a server compromise to add HTML5 canvas is quite unlikely.) So I wouldn’t know what I did wrong.

Not using any plugins (except the default docker manager plugin).

Using default theme.

Yes, I can confirm I also noticed same on the Tor browser.

On or on


Can’t reproduce on neither.

In which forum is it happening for you?

  • In the forum where I am admin? (Don’t want to advertise it here, no need.)
  • Or you don’t know me (good, in this case, ha) and it is happening for you in another forum?

Does it happen for you in or on