Cookie Syncing

What is Cookie Syncing?

A process in which multiple parties share and match their identification ids for a particular user. The benefits of cookie syncing generally include:

• Buyers will have more data on their audiences, leading to more precise buys with stronger KPIs.
• Sellers will be able to sell more inventory, generating more revenue.

How does Cookie Syncing Work?

Cookie syncing works by the SSP serving a tag (provided by the demand partner) on publisher pages, enabling the demand partner to associate an ID with the user. Next the demand partner passes its ID back to the SSP, who in turn stores the ID, ready to pass in the bid request next time we see the user. Kind of like a game of hot potato, if hot potato was played in the world of ad tech.

Because an auction needs to be resolved as quickly as possible to avoid missed revenue opportunities, there’s not enough time to conduct cookie syncing before we start the auction. This means there will always be some bid requests that go out without the demand partner’s user ID.

We initiate cookie syncing on every page impression for all of our demand partners. For a subset of our demand partners, they also initiate cookie syncing when they see users (e.g. when they serve ads on other exchanges). This reduces the instances of bid requests going out with demand partner user IDs.

Step by Step

1. A user visits a website that contains an ad.
2. The browser sends an ad request to an ad exchange.
3. The ad exchange sends back the request and creates a (third-party) cookie.
4. 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 ad exchange along with its own user ID in the cookie-matching table.
5. If the sync is bidirectional, the DMP makes the redirect back to the ad exchange, passing its own ID in the URL parameter. The ad exchange receives this request, reads its own cookie, and stores the DMP ID along with its own ID in the cookie-matching table.
6. Now, both the ad exchange and DMP have each other’s’ user IDs in each other’s databases.

Note: in the diagram below DSP can be interchanged with DMP and SSP can be interchanged with Ad Exchange. The main takeaway here is that the buying and selling parties in a transaction that share their user ids to create a better picture of the user. Cookie syncing can happen simultaneously across many different sellers in one auction. Lastly, cookie-syncing can also be one-directional in nature where the only one party shares their user information while the other party does not pass back any information from their end.

Sources

• https://unruly.co/blog/article/2017/10/09/cookie-syncing-what-is-it/
• https://clearcode.cc/blog/cookie-syncing/
• http://www.adopsinsider.com/ad-exchanges/cookie-syncing/

I’m just always looking forwards. I spend very little time, looking backwards

— Gary Vaynerchuk