VPAID

Video Player Ad-serving Interface Definition, or a follow-on spec released by the IAB in 2009 that also allowed ad servers and video players to talk to each other — but was meant to better support rich media (such as overlays that people could click on to learn more about a product or brand). In practice, it was mainly used for measurement and verification and became overloaded, which resulted in broken user experiences, especially on mobile. It’s currently being phased out and replaced by SIMID (see below).