What is canvas fingerprinting?
Canvas fingerprinting is one of a number of browser fingerprinting techniques of tracking online users that allow websites to uniquely identify and track visitors using HTML5 canvas element instead of browser cookies or other similar means.
Canvas fingerprinting works by exploiting the HTML5 canvas element. When a user visits a website with canvas fingerprinting, their browser is instructed to “draw” a hidden line of text or 3D graphic that is then converted to a digital token. Variations in which GPU is installed or the graphics driver cause the variations in the rendered digital token. The token can be stored and shared with advertising partners to identify users when they visit affiliated websites. A profile can be created from the user’s browsing activity allowing advertisers to target advertising to the user’s inferred demographics and preferences.
How to prevent canvas fingerprinting in Slimjet or Chrome
Since canvas fingerprinting relies on reading data from the canvas element, we can effectively prevent any canvas fingerprinting by disabling such data reading. Fortunately, Chrome provides a hidden switch “–disable-reading-from-canvas“ for this purpose. But hey, who wants to type a long command line switch just to flip an option?
To make things more convenient for users, we have added an option in Slimjet to easily prevent /stop any canvas fingerprinting attempt. Just select ”Settings” from the menu and scroll down to the “Security” section. Then, turn on the option “Disable reading from HTML5 canvas” as shown in the following screenshot:
After that, you need reload all existing tabs from the settings to take effect.