What are advertising passback tags and common implementation

Question

I'm using Google Adsense as a Publisher and am trying to also use another ad-network. They specified I should implement a passback tag and send it to them.

What is a passback tag? pseudo implementation details?

Answer 1

Passback or default tags can be any network or remnant tags that you use to fill inventory. When your primary ad-network doesn't have anything to serve (for example, there isn't an advertiser willing to pay a high enough CPM), you can send that impression back to your default advertiser's tags to serve. This will allow you to monetize every impressions, and greatly reduce the chance of serving blank ads.

Passback tags allow you to implement a so-called waterfall model, which allows to show another banner from current placement in case the previous one has failed to be displayed and discount the impression for the banner which has not been shown.

In your example, say that your alternate ad-network provides a higher CPM than Adsense but only fills 40% of the time (ie, 40% of your impressions have ads served by alternate ad-network while the other 60% are blank). You could provide your AdSense ad unit code as a passback tag to the alternate ad-network so that for the 60% of impressions that they didn't provide an ad for, they would give Adsense an opportunity to fill those empty impressions.