The Programmatic Glossary
A practical glossary designed to help marketers, advertisers and ad-tech professionals understand the terminology that powers programmatic advertising
Identity & Data
Universal ID (UID)
A shared, privacy-compliant user identifier that multiple publishers and ad tech companies can all use to recognise the same user, without relying on third-party cookies. Universal IDs enable cross-site targeting and measurement to continue as cookies phase out.
HOW IT WORKS
A user provides their email address to a publisher, for example by signing in or subscribing. The publisher hashes this email (converts it to an anonymised code) and shares it with a Universal ID provider. Other publishers and advertisers using the same system can recognise the same hashed identifier, enabling targeting and attribution without exposing personal data.
EXAMPLE
A user logs into a news website with their email. The publisher shares their hashed email with a Universal ID provider. An advertiser has the same user in their CRM (Customer Relationship Management) system. When the user visits another participating publisher, the advertiser recognises them via the UID (Universal ID) and serves them a personalised ad. No cookie is needed.
RELATED TERMS
Third-Party Cookie | First-Party Data | Identity Solution | Retargeting | DMP (Data Management Platform)
★ LIMELIGHT INSIGHT: Limelight supports Universal ID integrations within its platform, helping publisher partners maintain identity-based targeting capability and premium CPMs (Cost Per Mille) in a post-cookie environment.
