- VAST document
- Wrapper chain
- Media loading
- Playback events
Use this sequence to organize the investigation. Confirm the details in the affected platform and campaign.
This guide covers a selected set of common diagnostic categories, not every code in every VAST version or SDK. Check the player's implementation and the official reference linked below when interpreting severity or vendor-specific behavior.
Begin with the original error value, timestamp, device, player version, and ad request. Some errors allow fallback or continued playback, so distinguish an error event from a complete failure to show any ad.
XML and compatibility errors
100 indicates an XML parsing problem; 101 concerns schema validation; 102 concerns an unsupported response version. Inspect the actual returned document rather than only the tag URL. An endpoint can return an HTML error page where XML was expected.
Check required fields and supported versions against the integration. Preserve the failing response so the supplier can reproduce the problem.
Wrapper errors 301, 302, and 303
301 identifies a VAST redirect timeout. Check reachability and response timing. 302 identifies a wrapper limit being reached; inspect excessive depth or looping redirects. 303 identifies an empty VAST response after wrappers.
These are different branches of the investigation. A longer timeout does not fix an empty ad response or a circular chain.
Media errors 401, 402, and 403
401 indicates that a media file was not found. 402 indicates a media-file timeout. 403 indicates that suitable supported media could not be found for the player.
Check the media URL, response, format, and affected device. Separate failure to resolve the VAST document from failure to obtain or play the media it references.
Collect an escalation packet
- Include timestamp, player and SDK version, device, and affected environment.
- Record the original error code and whether fallback played another ad.
- Preserve the request and returned XML with sensitive values removed as appropriate.
- List redirect and media statuses with response timings.
- Explain whether the issue reproduces consistently and what changed before it started.
Verify the outcome after a correction
Retest the same player and device with the corrected response or asset. Check successful starts and expected tracking, then compare the affected error category over a comparable period.
Use error rates with their stated denominators. A raw increase in errors during higher traffic does not by itself mean reliability worsened. For deeper wrapper investigation, continue to the dedicated timeout guide.
Test your reasoning: Choose the error branch
Original simulated exercise. This is not a real client case.
A failed attempt returns an inline response.
Evidence available
- VAST XML resolves.
- The media URL returns not found.
- The player reports 401.
Should the first fix be reducing wrapper depth?
Read the answer and next check
No. The evidence points to media availability after VAST resolution. Verify the media URL and asset hosting.
Next check: Retest media loading and playback on the affected player after the asset is corrected.