VAST error codes / NonLinear and companion
VAST error 501: NonLinear dimensions do not fit
Short answer: The overlay is too large for the display area.
Debug this tag now
If you only have a live URL, test it first. If the failure is in the wrapper chain, inspect each hop. Validate resolved XML when you already have the response.
What your player reported
501· Unable to display NonLinearAd because creative dimensions do not align with creative display area (i.e. creative dimension too large).
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 non-linear creative's dimensions do not align with the available overlay area.
Common causes
- Overlay larger than the slot
- Missing or wrong width/height on `<NonLinear>`
How to fix it
Set `<NonLinear>` width and height to fit the slot.
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-nonlinear-dimensions: <NonLinear> missing required width or height attributes
Related error codes
- VAST error 500: General NonLinearAds error
- VAST error 502: Cannot fetch NonLinear resource
- VAST error 503: No supported NonLinear resource
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