What is Unified ID 2.0 (UID2)?
Unified ID 2.0 (UID2) is an open-source advertising identifier, led by The Trade Desk, created from a person's hashed and salted email address or phone number when they log in to a participating site or app. It lets advertisers recognize the same consenting user across publishers without third-party cookies, and includes an opt-out portal.
Unified ID 2.0 tokens are encrypted and rotated, and participants sign terms governing use. Many DSPs, SSPs and publishers support it, and European Unified ID (European Unified ID) adapts it for GDPR. Critics, including privacy advocates, argue that email-based IDs are still persistent tracking identifiers.
UID2 is one of several alternative IDs, alongside LiveRamp's RampID and others. Because each needs logged-in users, reach is limited to authenticated audiences, which is why identity graphs and contextual targeting remain important.