VAST error codes / Wrapper errors
VAST error 303: No ads after wrappers
Short answer: One or more wrappers resolved but produced no inline ad.
Inspect the wrapper chain first
VAST error 303 is a wrapper-chain failure. Inspect each hop, then test the resolved tag.
What your player reported
303· No VAST response after one or more Wrappers.
Wording from the IAB VAST 4.3 specification error table. Players may shorten or reformat it, but the code is the same.
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.xml