VAST error codes / NonLinear and companion
VAST error 603: Cannot fetch companion resource
Short answer: The companion resource could not be loaded.
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
603· Unable to fetch CompanionAds/Companion resource.
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 resource URL did not resolve to a usable asset.
Common causes
- Broken resource URL
- HTTP resource blocked on an HTTPS page
How to fix it
Confirm the companion `<StaticResource>`/`<IFrameResource>`/`<HTMLResource>` is reachable over HTTPS.
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-resource: <Companion> must contain at least one StaticResource, IFrameResource, or HTMLResource
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