The Digital Video Ad Serving Template (VAST) macros are a powerful tool used for communicating a broad array of data points when delivering VAST ads.
When using Server Side Ad Insertion (SSAI) technology for ad delivery, there may be a lack of reliable client-side data, which ultimately makes the data transmitted from macros all the more crucial.
The Digital Video Technical Standards Working Group has recognized a number of common use cases for SSAI and put together a list of recommended macros that helps direct SSAI providers and the industry toward an optimal set of relevant macros. The list contained within the SSAI VAST Macros Guidance has been curated for sharing basic user agent, environment, and content details that are critical to verification partners and buyers. As companies adopt these recommended macros as best practices the industry stands to gain in increased transparency and efficiency.
The official IAB Tech Lab maintained list of VAST 4x Macros now contains over 50 VAST macros and continues to grow as new use cases are uncovered. While some of the macros on the list are considered required, many remain optional. The variety of needs from one organization to the next have left the selection of macros that end up implemented open to a certain degree of interpretation. Additionally, including every single macro from the list is prohibitive given URL length limits for HTTP GET requests (an issue being addressed separately by the Common Ad Transport Standard or CATS).