VAST error codes / NonLinear and companion
VAST error 601: Companion does not fit
Short answer: No display space for the companion's dimensions.
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
601· Unable to display Companion because creative dimensions do not fit within Companion display area (i.e., no available space).
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 companion creative's dimensions do not fit the available companion slot.
Common causes
- Companion larger than the slot
- Missing or wrong width/height on `<Companion>`
How to fix it
Set `<Companion>` width and height to match an available 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-companion-dimensions: <Companion> missing width or height
- VAST-3.0-companion-required-attr: <CompanionAds> required attribute must be all, any, or none
Related error codes
- VAST error 600: General CompanionAds error
- VAST error 602: Required companion not displayed
- VAST error 603: Cannot fetch companion resource
- VAST error 604: No supported companion 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