Matching users using a Universal ID provider

Media Owners
Last Updated: February 12, 2026•

At Index Exchange (Index), a Universal ID provider refers to an identifier associated with users or devices, and is commonly used by all providers across the supply path. Buyers who use a Universal ID provider can enable audience targeting that uses user data such as brand or publisher first-party data, remarketing, and behavioral targeting. By enabling a Universal ID provider, Media Owners can pass a Universal ID to buyers in the bid request. Buyers who have enabled the same Universal ID provider as the Media Owner can use the Universal ID to connect the user to the corresponding data that they have saved.

Publishers benefit from using a Universal ID provider because buyers are willing to bid higher when they have a notion of a user or device. As a result, Media Owners who use a Universal ID provider typically receive higher bids.

Buyers benefit from using a Universal ID provider because they can more effectively reach specific audiences through the open market or through a deal ID. As a result, buyers can deliver the right message to relevant audiences, creating a more personalized experience, as well as control ad frequency and measure results.

Index supports two types of Universal IDs to help Media Owners and buyers better identify their users:

  • Authenticated ID: A type of Universal ID that is based on user-level information such as an anonymized email address or phone number. This type of ID can associate a known user across multiple devices.

  • Inferred ID: A type of Universal ID that is used when an email address or phone number isn't available to brands or Media Owners. Unlike an authenticated ID, an inferred ID is device-level. It's created when a user visits a publisher's site and is used to retarget that same user when they make future visits on publisher sites.

For more information about how to enable a Universal ID provider, Media Owners can refer to or Send Universal IDs in bid requests for server-to-server integrations.

Supported Universal ID providers

At Index, we currently support the following Universal ID providers:

  • 33Across

  • Central and Eastern Europe ID

  • Criteo

  • Epsilon

  • European Unified ID (EUID)

  • First-id

  • Google PAIR ID

  • ID5

  • LiveIntent

  • LiveRamp

  • Loblaw LMPID

  • Lotame

  • netID

  • NovatiqId

  • SharedID

  • TrustPid

  • Unified ID

  • Utiq

  • Yahoo ConnectID

For more information on our supported Universal ID providers, see List of supported identifier providers.

How Universal IDs are passed in bid requests

Number one icon

When a user visits a publisher site with a Universal ID provider enabled, the Media Owner's integration has a set amount of time to retrieve a Universal ID and include it in the bid request before a timeout occurs. The following will occur depending on whether a Universal ID is available:

  1. If a Universal ID is available and retrieved before the timeout occurs, the workflow continues to step two.

  2. If a Universal ID is not available, the Media Owner's integration calls the Universal ID provider's endpoint. If the user provides consent, a new ID is created and cached in the browser's local storage. If the request is originating from the European Union (EU), the user is shown a message asking for consent to use and store their information, and Index receives a TCF 2.0 string to pass along in the bid request. The workflow continues to step two.

  3. If the user does not provide consent or a Universal ID is not retrieved before the timeout occurs, the bid request is passed without a Universal ID and the workflow ends.

  4. If the Universal ID is not retrieved before the timeout occurs but the user has provided consent, a Universal ID is still collected and saved in the browser's local storage for future impressions.

Number two icon

If a Universal ID is retrieved before the timeout occurs, it is made available to Index using one of the following methods depending on the Media Owner's integration type:

  1. Prebid.js integration: The Universal ID is made available to the Index adapter through the bidrequest.userIdAsEids object. For more information about how to enable support in Prebid.js, see Index's adapter documentation.

  2. OpenRTB server-to-server integration: The Universal ID is made available through the user.ext.eids object. For more information about how to include this in the bid request, see Send Universal IDs in bid requests for server-to-server integrations.

Note: If the Media Owner is using a Universal ID that requires decryption, there will be an encrypted envelope that contains the Universal ID that is decrypted in step three.

Number three icon

Depending on the Universal ID provider that the Media Owner has enabled, one of the following will occur:

  1. The Index-supported Universal ID is decrypted or transformed into a unique ID for each eligible DSP. It is then passed to all eligible DSPs who are enabled to receive it.

  2. If the buyer is using Index's Matched Audiences™ solution, any Universal ID providers who support Matched Audiences pass a buyer's audience file to the Index Audience Manager. Index validates and deploys the audience file to the Index ad server. Index or the Media Owner creates a deal ID for the audience.

    If a user from the buyer's audience file visits the Media Owner's site, Index checks if the user matches the criteria for the deal ID. If the criteria matches, Index passes the bid request to the eligible DSP.

  3. If the Media Owner has enabled LiveRamp, their Universal ID is decrypted or transformed into a unique ID for each eligible DSP. It is then passed to all eligible DSPs who are enabled to receive this Universal ID.