The 10 VAST Errors That Silently Kill Your CTV Ad Revenue

Originally published on Medium. Samsung TV Plus just crossed 100 million monthly active users. Netflix ended 2024 with 277.6 million subscribers worldwide, 70 million on its ad-supported tier. Amazon Prime Video had 230 million users. Roku reported 89.8 million active accounts in Q4 2024. The ad spend flowing through all of it: $33 billion in the US alone in 2024 runs on VAST XML. Every impression, every pixel, every billing event depends on a tag being parsed correctly by players, ad servers, and measurement vendors that were built by different teams to different tolerances. Penthera found that 40% of VOD ads fail. Google Ad Manager flags any gap larger than 25% between impressions served and impressions counted as a sign of systemic VAST errors. Most of these failures trace back to a handful of tag-level mistakes that are trivially detectable before the ad ever reaches a player. I built an open-source tool that catches all errors mentioned below: vastlint. 108 rules across VAST 2.0 t