Here’s a step-by-step overview of how it works:
- A user visits a website that contains an ad.
- The DSP receives the ad request.
- The DSP sends back the request and creates a third-party cookie.
- The ad exchange redirects (http redirect) the ad request to the pixel URL on the DMP’s side, passing the user ID in the URL parameter. The DMP reads its own cookie, or creates a new cookie, and then saves the user ID passed from the DSP along with its own user ID in the cookie-matching table.
- If the sync is bidirectional, the DMP makes the redirect back to the DSP, passing its own ID in the URL parameter. The DSP receives this request, reads its own cookie, and stores the DMP ID along with its own ID in the cookie-matching table.
- Now, both the DSP and DMP have each other’s’ user IDs in each other’s databases.