Firefox 58 introduced a new feature, asking the user if we wants to allow HTML5 canvas image data for a website:

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

You can allow or deny the access, and you can always remember the decision.

How can I reset the decision once I have "always remembered" it (preferably individually for each website)?


You can find the permissions.sqlite sqlite database in your Mozilla profile folder, and then proceed to

SELECT * FROM moz_perms WHERE type = 'canvas/extractData';

From there you can decide which rows to keep or to delete with simple SQL delete statements, such as

DELETE FROM moz_perms WHERE type = 'canvas/extractData' AND origin = '<YOURSITEHERE>'

or of course via its id

DELETE FROM moz_perms WHERE type = 'canvas/extractData' AND id = <YOURID>

Please be careful when manipulating Firefox data, and be sure to backup your profile first.

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