VAST error codes / Wrapper errors
VAST error 303: No ads after wrappers
Short answer: One or more wrappers resolved but produced no inline ad.
What it means
The chain followed correctly but the final response was empty: a no-fill, an empty `<VAST/>`, or a `<VAST><Ad/></VAST>` with nothing to play.
Common causes
- Upstream demand returned an empty VAST (no-fill)
- Final hop returned a wrapper instead of an inline ad
- An ad object with no usable creative
How to fix it
This is often a legitimate no-fill rather than a bug. Inspect the last hop to confirm it returned an empty response, and make sure your no-fill handling is wired up.
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-ad-has-inline-or-wrapper: Each <Ad> must contain exactly one <InLine> or <Wrapper>
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.