What is Identity Resolution?
Also known as: UID2, ID5, Alternative IDs
Quick definition
Identity resolution links signals such as hashed emails, device IDs and contextual data into a persistent identifier so advertisers can target, cap frequency and measure without relying on third-party cookies.
Key points
- Deterministic
- Based on authenticated data such as hashed email (e.g. UID2, RampID).
- Probabilistic
- Infers identity from IP, device and behavioural patterns; higher scale, lower precision and more regulatory risk.
Benefits
- Restores addressability and measurement
Trade-offs
- Requires consent and log-ins
- Fragmentation across many ID providers
FAQ
Does identity resolution replace cookies?
Partly. It covers authenticated audiences well; contextual and cohort approaches are needed for the rest.
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Official sources
Last reviewed 2026-10-27. Explanations are written by AdTech Radar; consult the official specification for implementation.