EUID

European Unified ID (EUID) is an open-source framework that turns a consented email address or phone number into an encrypted advertising token, built on UID2 and adapted to EU and UK data protection law.

EUID follows the UID2 design. A user logs in or gives an email. The publisher or its partner sends the normalised, hashed address to an EUID operator, which returns a rotating token that can travel in bid requests. Only authorised participants can decrypt the token into a raw EUID.

The differences are legal. EUID has its own namespace, so EUIDs and UID2s do not match each other. Its consent model is driven by the GDPR, the IAB Europe Transparency and Consent Framework (TCF) and local guidance, while UID2 follows US state laws such as the CCPA and CPRA. Consumers can opt out at any time through the Transparency and Control Portal (EUID documentation, updated 2 November 2026). EUID covers websites, mobile apps and connected-TV apps.

The Trade Desk runs the public operator. A participant can also run a private operator, so hashed data stay inside its own environment and only tokens leave.

Example: In October 2024 the SSPs Criteo Commerce Grid, Google Ad Manager, Index Exchange and Microsoft Monetize announced EUID integrations, which let them pass on advertiser bids that include EUIDs (The Current, 25 November 2024).

Related terms: UID2, hashed email, TCF, ID5 ID, consent string.

Authoritative source: EUID documentation, "EUID overview" (last updated 2 November 2026).