VAST Error 300: General wrapper error
Something failed while following a wrapper redirect — the catch-all for wrapper problems that aren't a timeout (301), depth limit (302), or no-fill (303).
A wrapper is a VAST document that points at another VAST document instead of containing the ad itself. Error 300 fires when following that pointer fails for a reason the player can't classify more precisely: an invalid VASTAdTagURI, a DNS failure, a TLS error, an HTTP error status on a hop, or a redirect loop.
Because it's the catch-all, diagnosing 300 means resolving the chain hop by hop and finding which request breaks and how.
Why error 300 happens
Malformed or unresolvable VASTAdTagURI
The wrapper's redirect URL is broken — unescaped characters, an unexpanded macro left in the URL, or a hostname that doesn't resolve.
HTTP or TLS failure on a hop
A hop returns 4xx/5xx, or its certificate is invalid/expired. Mixed content also lands here: an HTTPS player refusing an HTTP-only hop.
Redirect loop
Hop A points to B which points back to A. The player detects the cycle and abandons the chain.
Unexpanded macros in the redirect URL
Literal [CACHEBUSTING] or [TIMESTAMP] strings left in the URI break signature checks or routing on the next server.
How to fix VAST error 300
- 1
Resolve the chain hop by hop
Run the tag through a validator that follows wrappers and shows each hop's URL, status code, and latency. The failing hop is immediately visible.
- 2
Check the failing hop's URL for macros and escaping
Look for literal macro placeholders and unescaped & in the VASTAdTagURI. Fix macro expansion at the server that emits the wrapper.
- 3
Verify HTTPS on every hop
Every URL in the chain must be HTTPS with a valid certificate. One HTTP hop breaks the chain for secure players.
- 4
Contact the owner of the broken hop
Each hop belongs to a specific partner. Send them the exact failing request and response — the chain trace makes attribution unambiguous.
Seeing error 300 on a live tag?
Paste the tag URL or XML — the validator resolves the full wrapper chain, validates the schema, downloads every media file, and shows exactly which stage fails.
Validate your VAST tagVAST error 300 — frequently asked questions
How do I tell error 300 apart from 301, 302, and 303?+
301 is specifically a timeout, 302 specifically too many hops, 303 specifically an empty response at the end. 300 is everything else that can go wrong following a wrapper — bad URLs, HTTP errors, TLS failures, loops.
Can I see the wrapper chain without special tooling?+
You can curl each VASTAdTagURI manually and follow the chain yourself, but a VAST validator automates it — resolving every hop and reporting status, latency, and the final inline ad in one pass.
Who is responsible for fixing a 300?+
The owner of the hop that fails. The chain trace tells you whose server emitted the broken redirect and whose server failed to answer — that's where the fix belongs.