vastlint
VAST-2.0-flash-mediafile

VAST-2.0-flash-mediafile

Flash-based MediaFile type is no longer supported

WarningDeprecatedIAB VAST 2.0 §2.4.1VAST 2.0 and later (all versions)

Short answer

Flash (SWF) media files have not been supported in any major browser or device since 2020. Serving a Flash <MediaFile> will result in zero impressions.

Why this matters in production

This rule is a strong risk signal. Tags with this issue often still parse, but they become brittle across SDKs, SSAI resolvers, and CTV environments. Deprecated features are a long-tail compatibility problem: they may appear to work in one legacy stack and fail silently in newer players, SSAI chains, or device ecosystems. Affected scope: VAST 2.0 and later (all versions).

How to fix

Remove the Flash SWF <MediaFile> and serve an HTML5 video asset (MP4 or WebM) instead.

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