UID2 & ID5
UID2 & ID5 explained
An identifier can help connect events within a supported data flow. It does not establish whether the match is correct or whether advertising causes an additional outcome. First define the task: reaching a particular segment, limiting repetition or supplementing measurement? Then check which publishers, platforms, regions and data are actually covered. A vendor logo on a partner list is not a complete integration test.
UID2 uses deterministic identity inputs such as email addresses or phone numbers. EUID needs separate consideration in the European context: it builds on the UID2 framework but is a standalone solution with its own namespace. Its official overview distinguishes privacy and consent requirements in particular. Do not treat UID2 and EUID as interchangeable identifiers. Check the specific regional solution and participation terms.
ID5 describes a combination of direct signals and probabilistic methods. Different sources can lead to different matching quality. Operating without an email login does not mean operating without personal data or required permission. ID5’s requirements call for appropriate information about data flows, roles and user choices. Pseudonymisation is not anonymisation. Even technically supported connections between solutions need specific setup and checks.
Creative Engineering connects a relevant campaign idea with testable data quality. We take responsibility for the concept and quality. Test matching, coverage, opt-out and failure cases using suitable data. AI-assisted linking does not replace this control. Compare full integration, data and media costs against a suitable alternative. A high match rate may include false connections; a higher price per thousand contacts does not establish greater advertising impact.
Examples
Hypothetical application
An advertiser evaluates a limited identity integration with a publisher and buying platform. The pilot documents the regional solution, permissible data, reachable contacts and exclusions. An appropriate comparison then examines whether the additional functionality justifies its total effort.
Key Points
- Treat UID2, EUID and ID5 as distinct, specific solutions.
- Check coverage, matching quality and conditions of use separately.
- Do not equate more connected signals with better impact.
Practical application
Start with a clearly bounded use case and document the source data, regional solution, partners and choices. Test matching quality and overall in a pilot.
Useful measures
Usable coverage
Share of contacts lawfully reachable for the specific purpose; state the population and region.
Matching quality
Distinguish correct, false and missing connections using suitable validation data.
Incremental economic value
Evaluate the integration against an appropriate comparison, including data, technology and media costs.
Common mistakes
- Assuming global coverage or automatic interoperability for every solution.
- Treating pseudonymous or probabilistic matching as exempt from privacy requirements.
- Equating match rate, higher impression prices or attribution with incremental impact.
Sources and context
- Unified ID 2.0: Overview
Provider background on the framework and integration.
- European Unified ID: Overview
Distinguishes EUID and UID2, their separate namespaces and European context.
- ID5: Passing Signals to ID5
Technical context for direct signals and probabilistic matching.
- ID5: Privacy Policy Requirements
Vendor requirements for actual data flows, roles and user choices, not general legal clearance.
- EUR-Lex: DSGVO / GDPR
EU legal basis, particularly purpose limitation, data minimisation, lawful bases, consent and marketing objections.
Frequently Asked Questions about UID2 & ID5
No. EUID documentation describes a standalone framework with its own namespace. The actual regional integration must be appropriate.
No. A pseudonymous identifier can still be personal data. Data flows, purposes, roles and required user choices remain relevant.
It initially describes successful technical connections under a particular definition. False matches, coverage and actual usefulness need additional assessment.
Related links
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