Unique User Identifier (UUID)

AdTech platforms use a unique user identifier (UUID) — stored in a cookie — to identify and track users across sessions and properties without relying on personally identifiable information (PII) such as a name or email address. The UUID acts as a pseudonymous stand-in: the platform can recognize a returning user and build a behavioural profile against that identifier while keeping any directly identifying data out of the tracking layer entirely.

This approach is a foundational privacy trade-off in adtech infrastructure. By decoupling identity from real-world personal details, platforms can maintain audience continuity and frequency management while reducing the exposure risk associated with handling PII directly.