VAST error codes / Wrapper errors
VAST error 304: Inline displayed too slowly
Short answer: An inline ad resolved but did not display within the time limit. Introduced in VAST 4.0.
Inspect the wrapper chain first
VAST error 304 is a wrapper-chain failure. Inspect each hop, then test the resolved tag.
What your player reported
304· InLine response returned ad unit that failed to result in ad display within defined time limit.
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 produced an inline ad, but rendering did not complete inside the player's defined window.
Common causes
- Heavy creative or slow media that exceeds the display deadline
- Late-resolving assets in the inline ad
How to fix it
Profile the inline creative's load time and trim wrapper latency so the inline ad has time to render.
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 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