• Adda
    10·
    3 years ago

    I would direct you towards the same question on Tor StackExchange. I think the Tor Project documentation explains the problems with canvas fingerprinting quite nicely. Hope it helps understand the risks and the purpose of this permission.

  • substantial_kek
    3·
    3 years ago

    It’s worth noting this permission can be used for legit reasons sometimes, like for rendering some graphical elements. But most of the time it’s used for fingerprinting your browser. And it’s so widespread, you can see it everywhere from government websites to Linux distro websites. Crazy stuff.

    • KrustyOP
      1·
      3 years ago

      Thank you! Is there a way I can understand what is this permission for and/or if it’s for legit reasons?

      • substantial_kek
        2·
        3 years ago

        Not sure. I usually block it by default and see if everything works alright. If some graphical glitches start to apper, then maybe it’s related to this.

      • pinknoise
        2·
        3 years ago

        A canvas is an element of the website that can be drawn to from javascript. The result of some drawing operations can have subtle differences between devices which can aid in fingerprinting your specific device. (e.g. because of different fonts, gpu’s and gpu drivers) To do so the tracking script has to read the current raw-pixel content of the canvas to evaluate it. Reading the raw image data is what this permission (should) block, so websites can still use canvas, but not fingerprint your device with it.

        Legit applications for reading from the canvas could be games, simulations, and other computing stuff which your average website is unlikely to need to do.

  • mekhos
    43·
    3 years ago

    Basically, It can be used to dermine your display resolution.