VAST was introduced by the IAB in 2008 as a common protocol designed to improve compatibility between video ad servers and the growing variety of video players (and websites/devices they are viewed on), and it has since been updated to reflect ongoing innovations in video advertising.
The VAST script includes information such as when the ad should play, calls to action, and whether the ad can be skipped. VAST allows for the delivery, measurement, and tracking of in-stream video advertising, ensuring a seamless viewing experience and enabling advertisers to run large-scale targeted campaigns with multiple publishers across multiple video players.
However, other than the limited metrics reported back to the ad server, VAST only supports one-way communication from the ad server to the video player. For details on the additional interface required to serve interactive video ads – which require two-way communication, such as viewability measurement – see VPAID.