While the industry celebrated the “death of the third-party cookie,” advertising platforms built a more persistent and standardized identity system based on your email address.
Unified ID 2.0 (UID2) is now powering a significant portion of open-web advertising. Created by The Trade Desk and open-sourced, it standardizes how companies turn email addresses into stable identifiers.
How UID2 Works
UID2 has two layers:
Raw UID2: A static SHA-256 hash (Base64) of your normalized email address. Deterministic and permanent — same email = same hash everywhere.
