VAST error codes / Linear and media errors
VAST error 403: No supported media file
Short answer: No MediaFile matched a type/format the player can play.
What it means
Media files were present, but none had a MIME type, delivery method, or API framework the player supports.
Common causes
- Only formats the device cannot decode (e.g. browser-only on CTV)
- Deprecated VPAID/Flash media where the player needs MP4/HLS
- Missing or wrong `type` / `delivery` attributes
How to fix it
Make sure at least one `<MediaFile>` is a widely supported progressive or adaptive format with correct `type` and `delivery`.
VAST error codes are runtime buckets emitted by the player. They tell you where the failure happened, not which line of XML caused it. Paste the raw tag into the validator to map this code onto the exact element and rule.
Related vastlint rules
- VAST-2.0-mediafile-type: <MediaFile> must have a type attribute
- VAST-2.0-mediafile-delivery: <MediaFile> must have a delivery attribute
- VAST-2.0-flash-mediafile: Flash-based MediaFile type is no longer supported
Related error codes
Debug this tag now
Validate the XML, follow the wrapper chain, or check it in CI before launch:
# CLI: exits non-zero on errors, ideal for pipelines
vastlint check creative.xmlUse the right tool for this failure
If you already have the resolved XML, run a pure spec check. If you only have a live tag URL, test that endpoint first. If the failure happens in the wrapper chain, inspect each hop.