VMAP (Video Multiple Ad Playlist) is the IAB companion to VAST that describes the ad schedule for a piece of content: where the breaks are (pre-roll, mid-rolls at given times, post-roll) and what each should contain. Where VAST describes a single ad, VMAP describes the whole timeline of ad opportunities.
A player or SSAI stitcher reads the VMAP to know when to call for ads and how to place them, then uses the VAST responses to actually play them. VMAP is essential for structured ad experiences on long-form and live content, and it works alongside SCTE-35 markers that signal the break points within the stream.
