canvas fingerprinting
n. A technique for tracking a user online that involves drawing a hidden element on the browser canvas to create a token that uniquely identifies the user's computer.
Other Forms
The mechanism, called "canvas fingerprinting," uses special scripts — the coded instructions that tell your browser how to render a website — to exploit the browser's so-called 'canvas', a browser functionality that can be used to draw images and render text.
First documented in a forthcoming paper by researchers at Princeton University and KU Leuven University in Belgium, this type of tracking, called canvas fingerprinting, works by instructing the visitor’s Web browser to draw a hidden image. Because each computer draws the image slightly differently, the images can be used to assign each user’s device a number that uniquely identifies it.
—Julia Angwin, “Meet the Online Tracking Device That is Virtually Impossible to Block,” ProPublica, July 21, 2014
2012 (earliest)
It is worthwhile to note that these methods do preserve the same origin policy — if an image from a different origin has been drawn on this canvas, they will throw a SecurityError exception instead of returning pixel data. Therefore, our <canvas> fingerprints must only contain image resources that are under our control.
—Keaton Mowery & Hovav Shacham, “Pixel Perfect: Fingerprinting Canvas in HTML5” (PDF), Proceedings of Web 2.0 Security & Privacy 2012, May 24, 2012