Meet the Online Tracking Device That is Virtually Impossible to Block

A new, extremely persistent type of online tracking is shadowing visitors to thousands of top websites. 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.

Like other tracking tools, canvas fingerprints are used to build profiles of users based on the websites they visit -- profiles that shape which ads, news articles, or other types of content are displayed to them.