Fingerprinting

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.