Also known as: device fingerprinting · canvas fingerprinting
Browser fingerprinting is a tracking technique that identifies a user by combining observable characteristics of their device and browser — screen resolution, installed fonts, graphics rendering behaviour, time zone — into a signature distinctive enough to recognise across sites.
Fingerprinting requires no stored identifier, which is what makes it resistant to cookie clearing, private browsing, and consent controls. Users generally cannot see it happening and cannot straightforwardly opt out.
Countermeasures work either by making many users look identical, as the Tor Browser does by standardising reported values, or by randomising values so the fingerprint is unstable across sessions. Both impose usability costs, which is why adoption outside privacy-focused browsers has been limited.
Third-Party Cookie
A third-party cookie is a cookie set by a domain other than the one shown in the address bar, historically the primary mechanism allowing advertising networks to track individual users across unrelated websites.
Anonymization
Anonymisation is the process of altering data so that individuals can no longer be identified from it, either directly or by combining it with other available information — as distinct from pseudonymisation, which only replaces identifiers with reversible tokens.
Data Broker
A data broker is a company that collects personal information from public records, commercial transactions, apps, and online activity, then aggregates and sells it to other organisations — typically without any direct relationship with the individuals concerned.
Metadata
Metadata is the information surrounding a communication rather than its content — who contacted whom, when, for how long, from where, and how frequently — which remains visible even when the content itself is encrypted.
Surveillance
Surveillance in the privacy context refers to the systematic monitoring of individuals' communications, movements, or behaviour, whether conducted by states for security purposes or by companies for commercial ones.