Fingerprinting is a practice in which websites identify a particular browser (and by extension, a particular user) by collecting and combining distinguishing features of the browser and underlying operating system. Elements of a fingerprint might include, for example:

  • the browser version
  • the timezone and preferred language
  • the set of video or audio codecs that are available on the system
  • the fonts installed on the system
  • the state of the browser's settings
  • the computer's display size and resolution

A website can retrieve information like this by executing JavaScript and CSS on the device, and by combining this data can often create a unique fingerprint for a browser, which can then be used to track users across the web.

Web standards are designed in such a way as to minimize the ability of a website to collect identifying information, and browsers typically add their own protections as well.

See also