Unified IDs

The Trade Desk supports these Unified Identifier (UID) solutions, which offer significant advantages over third-party cookies:

Designed with the needs of modern marketers in mind, these solutions provide holistic targeting and measurement for an internet that’s becoming more privacy-conscious. Both UID2 and EUID are open-source frameworks that publishers, advertisers, and digital advertising platforms can use to establish identity without cookies. Both frameworks enable publisher websites, mobile apps, and Connected TV (CTV) apps to monetize through programmatic workflows. Built as a standalone solution with its own unique namespace, each framework offers user transparency and privacy controls designed to meet local market requirements. For differences between the two frameworks, see EUID vs. UID2.

NOTE: Most of the data integration solutions and Measurement APIs provided by The Trade Desk support UID2 and EUID.

Term definitions

The following table provides high-level definitions of the terms used on this page.

Term Definition
PII Personally identifiable information refers to personal data, such as email addresses and phone numbers, that can be used to identify a specific user. Also known as directly identifying information (DII).
UID2 Unified ID 2.0 is a deterministic identifier based on PII (either email addresses or phone numbers) with user transparency and privacy controls to meet the market requirements outside Europe and the UK. For details, see the UID2 documentation.
EUID European Unified ID is a deterministic identifier based on personal data (either email addresses or phone numbers) with user transparency and privacy controls to meet the market requirements only in European regions. For details, see the EUID documentation.
UID "Unified identifier (UID)" is a generic term that's used to refer collectively to UID2 and EUID.

NOTE: The terms "EUID" and "UID2" can refer to either the framework or an actual identifier. Unless otherwise indicated, this page refers to the respective framework.

EUID vs. UID2

EUID is an open-source, standalone solution with its own unique namespace that builds on the UID2 framework. The main differences between UID2 and EUID result from more stringent European and UK data protection laws relating to consent practices, rights for data subjects, and obligations between participants. Otherwise, EUID follows the same guiding principles as UID2.

IMPORTANT: Even though it is built on the UID2 framework, EUID is a separate framework.

The following table summarizes the key differences between the two frameworks.

Comparison Aspect UID2 EUID
Open-source framework Yes Yes
Type of personal data used Email addresses, phone numbers Email addresses, phone numbers
Consent management Based on local regulations such as the California Privacy Rights Act (CPRA) and the California Consumer Privacy Act (CCPA). Driven by the General Data Protection Regulation (GDPR), the Transparency and Consent Framework (TCF) operated by IAB, and local regulatory guidance.

Raw IDs vs. tokens

There are two types of Unified IDs: raw UIDs (also known as advertising IDs) and UID tokens (also known as advertising tokens). The following table explains each type.

ID Type Shared in Bidstream? Description
Raw UID2 or EUID No A raw alphanumeric identifier created through the respective UID2 or EUID APIs or SDKs with the user's DII as input.
To prevent re-identification of the original personal data, each raw UID uses hashing and salting. Raw UIDs are designed to be stored by advertisers, third-party data providers, and demand-side platforms (DSPs).
UID2 or EUID token (advertising token) Yes An encrypted form of a raw UID2 or EUID. UID tokens are generated from hashed or unhashed DII that is converted to raw UIDs and then encrypted for additional protection in the bidstream.
UID tokens are designed to be used by publishers or publisher service providers. Supply-side platforms (SSPs) pass UID2 or EUID tokens in the bidstream and DSPs decrypt them at bid request time.

See also Unified ID 2.0 Glossary in the UID2 documentation.

Who can benefit from using unified IDs

With its transparent and interoperable approach, UID2 and EUID both provide a collaborative framework for many participants across the advertising ecosystem—advertisers, publishers, DSPs, SSPs, single sign-on (SSO) providers, customer data platforms (CDPs), consent management providers (CMPs), identity providers, third-party data providers, and measurement providers.

For the benefits of using Unified IDs for the key participants, see the following UID2 documentation:

For details about using these IDs, refer to these pages: