ID5 Universal ID

Building a common language for digital advertising

To learn how to implement Universal ID on your website, please read our Prebid or ID5 API documentation.


Identity is at the core of digital advertising as data-driven campaigns generate most revenue for publishers. However, current user identification methods based on 3rd party cookies and MAIDs have reached their limits:

  • Browsers and phone manufacturers are restricting access to 3rd party cookies and MAIDs, limiting the availability of users IDs for advertising
  • Publishers have to support cookie matching on their website, which creates page latency, privacy concerns and risks of data leakage
  • 3rd party cookie-based IDs are only temporary and device-specific and suffer from low match rates which impacts campaign performance and publisher yield

The ID5 solution

ID5 has built an efficient identification infrastructure that improves the ability to share user-level information within the programmatic ecosystem. ID5’s privacy-by-design solution respects user choices and their need for privacy. ID5 also limits the reliance on cookie matching and allows publishers to regain control of the user identification process.

ID5 enables publishers and advertisers to create and distribute a shared 1st party identifier to the entire ecosystem to enable targeting, frequency capping, measurement and attribution. Ad tech platforms connect with ID5, decrypt the Universal ID and improve their user recognition capabilities. ID5 ensures that users’ and publishers’ preferences are respected throughout the advertising value chain.

A comprehensive approach that increases addressability

To ensure that Universal ID values are consistent across the different websites distributing them to the advertising ecosystem, ID5 uses deterministic or probabilistic methods, depending on what signals are available.

Deterministic link

When websites are able to provide “hard signals” such as hashed email addresses or login / SSO IDs, ID5 uses them to anchor consistent identifiers across the websites that have collected them.

Probabilistic link

When “hard signals” are not available, ID5 processes “soft signals” using a proprietary algorithm to infer the uniqueness of a user across websites. This algorithm runs on a combination of information, including the IP address, user agent string, page URL and timestamp of the visit.

“Hard signals” used to power deterministic linkage are generally rare. By combining both methods, ID5 can maximise the number of addressable users which benefits both buyers and sellers of data-driven digital advertising.

The ID5 Universal ID creates benefits for the entire advertising value chain

Click on one of the images below to see what ID5 can do for your business.