Third-party data audience expansion

To expand audience reach and improve targeting, consider creating expanded audience segments using cross-device expansion, lookalike modeling, or both. The following table highlights the benefits of using cross-device expansion and lookalike modeling.

Expansion Option	Description
Cross-device expansion	Track user interactions with an ad across multiple devices and increase audience reach by associating seed data with additional devices. This ensures that the expanded audience is more accurate, leading to better forecasting and campaign results.
Lookalike modeling	To increase audience reach and improve targeting, identify users whose behaviors and characteristics are similar to those of the seed audience, based on the known characteristics and behaviors of an existing audience. Focusing on these users leads to higher engagement and more conversions.

NOTE: To expand your audience segment by age or gender, contact your Technical Account Manager.

Prerequisites

Before creating an expanded audience segment, be sure you have the following:

Agreed to additional contractual terms. As part of the agreement, you'll receive a brand ID to set the rate for audience expansion. For details, contact your Data Partnerships representative.
Existing audience segments to be used as the seed.

Expanded audience segments require one or more existing audience segments as a seed, or starting point, to generate a larger, more targeted audience segment.

Refresh process and timing

The Trade Desk monitors data taxonomies for new expansion configurations or changes in configurations. Expanded audience segments are queued for processing as refreshes.

Here's what you need to know about refreshes:

To avoid disrupting user delivery to your expanded segments, check that seed segments are always refreshed and populated with users.
Audience expansion configurations are used to model a new expanded user set during each refresh.
When expanded audience segments are refreshed, this expanded user set gets placed into the segment with a 30-day time to live (TTL).
In some cases, the overall size of a segment can exceed the limit for a single refresh. For details, see FAQs.

After the expanded audience segment is created, The Trade Desk performs the following tasks:

Monitors your taxonomy for new expansion requirements.
Adds relevant users to the expanded audience.

NOTE: Wait 24 to 48 hours for your expanded audience segment to populate with users.

Create the expanded audience segment

To create the expanded audience segment, use the POST /v3/thirdpartydata endpoint. Include all relevant attributes defined in Third-party data taxonomy design, such as the Buyable property, parent segment, display name, and provider element ID.

To configure your audience expansion settings, in the AudienceExpansion object, do the following:

Set the IsEnabled property to true.
In the ProviderElementIds array, add the provider element IDs of the audience segments you want to use as the seed.
Do any of the following that meets your preferences:
- For cross-device expansion, set the IsCrossDeviceExpansionEnabled property to true.
- For lookalike modeling, set the IsLookALikeExpansionEnabled property to true, then configure the lookalike-modeling settings as needed.
- For both, set the IsCrossDeviceExpansionEnabled and IsLookALikeExpansionEnabled properties to true, then configure the lookalike-modeling settings as needed.

NOTE: If both cross-device and lookalike modeling are enabled on a segment, the audience first expands based on cross-device expansion. The segment then uses this expanded group as the source for lookalike expansion.

The following is a POST /v3/thirdpartydata request body example with an expanded audience and both cross-device expansion and lookalike modeling options enabled.

{
  "ProviderElementId": "EXPANDED_SEGMENT_ID_PLACEHOLDER",
  "ProviderId": "PROVIDER_ID_PLACEHOLDER",
  "AudienceExpansion": {
    "Countries": [
      "CA",
      "US"
    ],
    "IsCrossDeviceExpansionEnabled": true,
    "IsEnabled": true,
    "IsLookAlikeExpansionEnabled": true,
    "ProviderElementIds": [ // These are the IDs of the audience segments you want to be used as the seed for expansion.
      "2131", 
      "2132", 
      "2133"
    ],
    "LastProcessedUTC": "2024-01-01T00:03:00",
    "LookalikeSettings": {
      "IncludeSeed": true,
      "MaxExpansionFactor": 5.0,
      "MaxSize": 1000000,
      "TopPercent": 10.0
    }
  },
  "Buyable": true,
  "Description": "Expanded audience of users currently in the market for flights.",
  "DisplayName": "Expanded Audience for Flights",
  "IsDirectIPTargeting": false,
  "ParentElementId": "2130",
  "ThirdPartyDataId": 10
}

After the expanded audience segment is created, set its rate with the brand ID provided by your Data Partnerships representative for audience expansion.

TIP: Regularly update your seed audience segments to ensure that your expanded audience segment remains current and relevant.

Retrieve audience expansion configurations

To view your audience expansion settings, send a query for your data segment and set the IncludeAudienceExpansionFlag property to 1. Optionally, you can include the PageStartIndex and PageSize properties for paginated results.

The following is a POST /v3/thirdpartydata/query request body example of how to retrieve the audience expansion configurations for a segment.

{ 
  "ProviderId": "PROVIDER_ID_PLACEHOLDER",
  "ProviderElementId": "EXPANDED_SEGMENT_ID_PLACEHOLDER",
  "IncludeAudienceExpansionFlag": true,
  "PageStartIndex": 0,
  "PageSize": null
}

NOTE: If the request uses a segment that has not enabled audience expansion, the AudienceExpansion object returns null.

The following is a POST /v3/thirdpartydata/query response body example with audience expansion configurations for a specific segment.

{
  "Result": [
    {
      "ThirdPartyDataId": 1234,
      "ProviderId": "PROVIDER_ID_PLACEHOLDER",
      "ProviderElementId": "EXPANDED_SEGMENT_ID_PLACEHOLDER",
      "ParentElementId": "ROOT",
      "DisplayName": "Test",
      "Buyable": true,
      "Description": "Test",
      "AudienceSize": null,
      "AudienceExpansion": {
        "IsEnabled": true,
        "IsCrossDeviceExpansionEnabled": true,
        "IsLookAlikeExpansionEnabled": true,
        "ProviderElementIds": [
          "EXPANDED_SEGMENT_ID_PLACEHOLDER"
        ],
        "LookalikeSettings": {
          "TopPercent": 4.00,
          "MaxExpansionFactor": null,
          "MaxSize": 6000000,
          "IncludeSeed": true
        },
        "LastProcessedUTC": "2026-03-11T14:06:46",
        "Countries": [
          "CA",
          "US"
        ]
      },
      "ReceivedIDsCount": 0,
      "ActiveIDsCount": 0,
      "LastUpdatedAtUTC": "2026-03-11T18:46:16",
      "ActiveIDsCountExpanded": null,
      "TaxonomyComplianceStatus": "Approved",
      "SubProviderId": null
    }
  ],
  "ResultCount": 1, 
  "TotalFilteredCount": 1, 
  "TotalUnfilteredCount": 1 
}

FAQs

The following is a list of commonly asked questions about expanded audience segments.

Is a seed for the expanded audience segment the same as a seed in Kokai?

No. The seed for an expanded audience segment is a general term referring to the starting point for audience expansion based on one or more audience segments.

What audience segments can I use for a seed?

You can use any existing audience segments, whether available for purchase or not, as the seed for expansion.

How do I select a country?

You can specify one or more countries using Alpha-2 / ISO 3166 standards.

Why is my expanded segment larger than my configurations?

Over time, audience expansion configurations, such as max size, max expansion factor, and top percent, can cause the overall size of the segment to exceed its limits.

How do lookalike settings interact with each other?

When lookalike settings are used together in any combination, the following interactions can apply:

The calculation for segments is resolved in the following order: top percent, max size, then max expansion factor.
Top percent prunes the highest-scoring users are eligible for expansion.
The max size and max expansion factor can cap how many users are included in the expanded user set.
- Max size caps based on its flat value.
- Max expansion factors cap using the seed audience size multiplied by the factor.
- If both max size and max expansion are set, the cap is the smaller value.

How do I deactivate an expanded audience?

To deactivate your expanded audience segment, set the IsEnabled property to false. This prevents new users from joining the segment, and existing users will gradually expire based on their TTL.