VAST-3.0-progress-offset
<Tracking event="progress"> requires an offset attribute
Short answer
The progress tracking event must have an offset attribute to tell the player at what point to fire the beacon. Without it, the player cannot determine when to call the URL.
Why this matters in production
This rule is usually a delivery blocker. Many players, SDKs, and ad servers will discard the response or skip the affected creative once this condition is hit. Ambiguous rules matter because undefined behavior shifts between vendors. Fixing them reduces the chance that two standards-compliant systems interpret the same tag differently. Affected scope: VAST 3.0, 4.0, 4.1, 4.2, and 4.3.
How to fix
Add an offset attribute to <Tracking event="progress">, e.g. offset="00:00:10" for 10 seconds or offset="25%" for quarter-view.
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