Passback

How a passback works

1. The slot asks the first ad server for an ad.
2. That server has nothing eligible: nothing sold, nothing above the floor, or nothing that matches this reader.
3. Instead of an empty answer it returns fallback code, usually another network's ad tag.
4. That code runs and the second source fills the slot.

The same idea goes by several names: passback, fallback, default ad.

Passbacks, waterfalls and header bidding

A chain of passbacks is a waterfall: the first source, then the second, then the third, each asked only if the one before passed. Header bidding asks several sources at the same time instead and lets them compete for each impression. For a site selling direct with one network underneath, a single passback is the simple version and usually all it needs.

What passbacks cost

• Time. Every hop is another round trip before the ad appears. Keep chains short.
• Counting. Two servers count the same impression slightly differently. Expect small discrepancies and check them.
• Frames. Some network code expects to run in the page itself. Served inside a sandboxed frame, it can come back blank.

The rules of the network underneath

Check what your network allows before you put anything above it. Google's AdSense rules allow non-Google ads on the same site or page, provided there are not more ads than content. Some networks ask to be the only ad code on the site.

How Pyrobid handles it

Each banner slot's fallback can be the ad code you ran before. Paste it once. It runs in your page rather than in a frame, so AdSense and the others fill as they do today, and it only runs when no direct campaign has booked the slot. By default the Advertise Here card takes one of those unsold views in ten, to bring in direct buyers, and you can untick that.