How does a passback tag work?

A passback tag (sometimes referred to as a backfill tag) is added to earlier “look” tag to provide more fill when the impression count is low. Generally the “first look” tag on a web page will pay the highest CPM rate but provide the lowest fill which is why adding a passback tag is often essential to maximize revenue for an ad placement. Frequently, publishers that use ad servers will set up a stack of passback tags under their first look tag to best optimize their revenue.

Here are a couple of examples of passback setups:

In-Stream CPM ad unit is set up to “first look”. The unit has 10% fill but pays $4 CPM. An IAB CPM ad unit is added as passback which has 20% fill and pays $3 CPM. An IAB CPC tag is added as a 2nd passback and has 95% fill and pays around $1 CPM.
In-Stream CPM ad unit is set up to “first look”. The unit has 10% fill but pays $4 CPM. An IAB Display ad unit (ie. Adsense or Google ADX tag) is added as a passback which has approx. 95% fill and pays around $2 CPM.

passback tag

Updated on August 9, 2016

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