What is browser fingerprinting?

Browser fingerprinting combines characteristics of a browser and its device to help distinguish it from other browsers. These characteristics can include screen dimensions, language settings, installed fonts and the way graphics are rendered.

A single characteristic is rarely distinctive. However, combining several can create a recognisable pattern that helps link visits without a conventional tracking cookie. Mozilla’s explanation of fingerprinting describes how websites can collect and combine these details.

A fingerprint is not a permanent or perfectly reliable identity. Browser updates, device changes and privacy protections can alter it or reduce its accuracy. Nevertheless, deleting cookies alone may not prevent recognition because the underlying characteristics can be collected again.

Fingerprinting is one form of cookieless tracking, but it is not outside privacy law. In the UK, for example, device-access rules apply to relevant fingerprinting operations, and using fingerprinting for online advertising requires consent.