Destination rejects the upload - causes and fixes
An upload can be rejected for size, duration, container, codec, processing, or account-policy reasons. Read the exact error message; the destination usually names the cause. Check container, codec, size, and duration first; account and region rules vary.
Check these first
- Read the exact composer / API error message.
- Check container and codec against the destination's published format list.
- Check size and duration against the limit for your surface and account.
- Check whether the file opens and plays normally on your device first.
Likely causes
- Container not in the published format list
Editing codecs (ProRes, DNxHR) are often rejected even when the container is common.
- Codec inside an accepted container is unsupported
MP4 / MOV can hold many video and audio codecs; some are not decoded.
- File size or duration over the limit
Each surface and account tier has its own cap.
- Corrupted or partial export
An interrupted export can look fine locally but fail to upload.
Fix it
- Re-export with a recommended preset
Use the registry's recommended preset for the destination; pick MP4/H.264/AAC unless a different combination is documented.
Re-export with a recommended preset - Run File Doctor to confirm the actual container and codec
The extension is a label, not the truth; the browser File Doctor reads bytes locally.
Run File Doctor to confirm the actual container and codec
Check your file
Extension and MIME type are labels, not proof of the container. Dimensions and duration come from this browser's media reader. This does not detect codecs, bitrate, corruption or platform upload compatibility. Files and measurements are not sent anywhere.
Prepare a copy in Koldflux, review its output and check the current destination requirements before publishing.
Automate this in Koldflux