Basically Canvas is a JavaScript API for programmatically drawing graphics and text. Subtle differences in color, font rendering, antialiasing etc will produce different rendering on different hardware depending on OS, browser, GPU, drivers, etc. This lets a site running JavaScript to generate a hash unique to everyone with your specific combination of software and hardware and uniquely identify you without cookies.
Basically Canvas is a JavaScript API for programmatically drawing graphics and text. Subtle differences in color, font rendering, antialiasing etc will produce different rendering on different hardware depending on OS, browser, GPU, drivers, etc. This lets a site running JavaScript to generate a hash unique to everyone with your specific combination of software and hardware and uniquely identify you without cookies.