VAST error code
300 — General wrapper error
What the spec says
Something went wrong resolving a wrapper that does not fall into the more specific 30x codes.
What actually causes it
- A wrapper with no VASTAdTagURI, so there is nothing to redirect to.
- A malformed redirect URL, frequently caused by an unencoded macro.
- The wrapped response failing in a way the player could not classify.
How to fix it
Resolve the chain by hand: fetch the wrapper, read its VASTAdTagURI, fetch that, and continue until you reach an inline response or a failure. The hop that breaks is usually obvious once you can see the chain.
To see whether a tag would hit this before it runs, paste it into the VAST validator. It reads the XML and reports the conditions that map to this code.
Related codes
Code definitions from the IAB Tech Lab VAST 4.3 specification. Causes and fixes are practitioner guidance, last verified July 2026.