VAST error code
405 — Problem displaying media file
What the spec says
The file was retrieved and accepted but failed during rendering or playback.
What actually causes it
- A corrupt or partially uploaded asset.
- A codec profile beyond what the device can decode, such as High profile on constrained hardware.
- An audio track in a format the device cannot handle, even when the video decodes.
How to fix it
Re-encode to a conservative baseline: H.264 Baseline or Main profile with AAC audio in an MP4 container. This code usually means the file is technically valid but too demanding for the device that received it.
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.