VAST error codes / Linear and media errors
VAST error 400: General linear error
Short answer: The player could not display the linear ad.
What it means
A catch-all for linear playback failures not covered by the more specific 401–411 codes.
Common causes
- No usable `<MediaFile>`
- A linear creative the player cannot render
How to fix it
Check the `<MediaFiles>` block. 401, 402, 403, and 405 are the specific cases.
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-linear-mediafiles: <Linear> must contain <MediaFiles> with at least one <MediaFile>
Related error codes
- VAST error 401: Media file not found
- VAST error 402: Media file timeout
- VAST error 403: No supported media file
- VAST error 405: Problem displaying media file
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.