VAST and VPAID tags act differently on both the demand and supply side.

VPAID Demand tags usually respond with a Bid even before having a specific ad to present. The ad manager, which loads onto the clients device, searches for relevant Demand after being loaded and winning the auction process. Meanwhile, VAST tags respond with a Bid only when there is an available actual ad to present.


It’s important to pay attention to the type of Traffic Channel that you export from the system due to the differences between VAST and VPAID.
VPAID Traffic Channels tags can call VAST tags and load them afterwards. VAST tags, on the other hand, can call VPAID tags but usually can’t run the JS in the response (depending on the player running the VAST tag with the VPAID demand). This can cause a discrepancy between the Demand Partner which provided the VPAID, and the Supply partner which exported a VAST tag from StreamRail.

In mobile pp activity, when you export a VAST Traffic Channel and your Publisher’s player supports only VAST, make sure to use the following Targeting condition in order to make sure your tag does not send traffic to VPAID Ad Sources which cannot be loaded afterwards: