Unified ID 2.0 (UID2)
Unified ID 2.0 (UID2) is an open-source, deterministic identity framework that turns a user's hashed and encrypted email or phone number into a privacy-conscious identifier for advertising across the open internet.
Key takeaways
- UID2 is a deterministic ID derived from a hashed, encrypted email or phone number.
- It is open-source and governed as industry infrastructure, not a single company's asset.
- It depends on user consent and authenticated first-party relationships.
- It aims to give the open web durable addressability after third-party cookies.
How UID2 works
When a user provides an email or phone number to a publisher and consents, it is hashed and encrypted into a UID2 token that can be passed through the bid stream. Because it's deterministic and rooted in authenticated first-party data, it survives cookie loss where anonymous IDs do not, while rotating and salting to limit exposure.
Why it exists and its limits
UID2 was seeded by The Trade Desk and handed to an independent operator model to serve as neutral, open infrastructure. Its ceiling is authentication: it only covers users who log in and consent, so it complements rather than fully replaces the reach of the old cookie-based web.
| Type | Deterministic, authenticated |
|---|---|
| Root signal | Hashed/encrypted email or phone |
| Governance | Open-source, independent operator |
| Limit | Requires login + consent |
Frequently asked questions
Is UID2 a replacement for third-party cookies?
It's a leading candidate for authenticated environments, but it only covers logged-in, consented users, so it complements contextual, first-party, and probabilistic approaches rather than fully replacing cookie-based reach.
Is UID2 privacy-safe?
It's designed to be privacy-conscious "” built on consent, encryption, and rotating tokens "” though, like any identifier, its real-world privacy depends on how consent and transparency are implemented.