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On several sites where I use Tor, I too often get the following popup message:

This website attempted to access image data on Canvas. Since Canvas image data can be used to discover information about your computer, blank image data was returned this time.

This is considerably intrusive and it's interrupting my work. How can I configure Tor browser to never again show this popup? Ok, it sent back blank image data - I get it. I'm happy with that. I just don't want to be reminded of it - ever.

I tried following the advice here in the accepted answer: HTML5 Canvas Image Extraction

However, that doesn't work (maybe something has changed since that version?) If I delete the permissions.sqllite file, then Tor just writes it back. Editing the file just seems to show a table definition (I wanted to change the value). If I can change this value to false, and this succeeds in removing this popup, where can I change it?

How can I get rid of this message so that it never again shows up, especially after requesting a new identity?

  • I must agree that the html canvas data pop up may be about a necessary bit of security but the method of using a pop up nag screen for every website is ridiculous and a major distraction. What dimwit programmer decided to employ a Chinese water torture technique to alert users of something they don't care to think about every three minutes? MAKE IT A TICK BOX AND LEAVE US ALONE. – user10220 Dec 16 '15 at 19:40
  • The options in this dialog include "Never for this site" and "Allow in the future" (really "Never for this session" and "Allow until Tor Browser closes"), but disregarding the fact that these settings aren't persistent across sessions, why isn't there a session-wide "Never for ANY site" option? (Like user10220, I find these popups EXTREMELY annoying.) – user1128 Jun 15 '16 at 1:05
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By default, Tor Browser does not remember your permissions to prevent linkability across different browsing sessions.

If you know what you're doing, go to about:config page and toggle permissions.memory_only preference to False. This should tell Tor Browser to remember your permissions about canvas.

  • Just did the about:config permissions memory toggled to False and it didn't work. – user10220 Dec 16 '15 at 19:52
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    I don't think this is what OP wants. They want to never again see the prompt, not just for this site. – l0b0 Jun 8 '17 at 22:29

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