Send user data matching requests to Index

DSPs
Last Updated: February 12, 2026•

DSPs can provide additional user data matching by pushing user IDs to Index Exchange (Index). Although Index provides the infrastructure to store all user matching data, we also support DSP-side user data matching storage.

To send user data matching requests to Index, the following process occurs:

Number 1 icon

The DSP drops a 1x1 pixel on the user's browser which contains one of the following Index user data matching URL.

  • If you want to push user match data for Index to store, use one of the following endpoints. Make sure to include the user ID (external_user_id) that you have assigned to the user.

    • https://dsum-sec.casalemedia.com/rum (for secure connections)

    • http://dsum.casalemedia.com/rum (for insecure connections)

  • If you want to store the user IDs, use one of the following endpoints when you initiate the user matching process. If you also want Index to store the match, include your user ID (external_user_id). Make sure to include the redirect URL (cb) in the request.

    • https://dsum-sec.casalemedia.com/rrum (for secure connections)

    • http://dsum.casalemedia.com/rrum (for insecure connections)

Number 2 icon

The pixel sends a request to the appropriate Index endpoint for user data matching. For more information about the fields that you can send in the request, see List of request fields sent to Index in DSP initiated user data matching.

Number 3 icon

Index adds the user ID (cmid) that it has assigned to the user and redirects the user to the DSP. For more information about the fields sent in the response, see List of response fields from Index in DSP initiated user data matching.