MP4 won't play or upload even though MP4 is supported - what's actually wrong
An .mp4 filename does not identify its codecs. Test playback in another player and inspect the actual streams in an editor. A browser playback failure alone does not prove corruption or upload incompatibility.
Check these first
- Inspect the actual video and audio codecs in an editor
- Compare the original in another player; decoder support varies
- Check whether an export was interrupted
Likely causes
- A listed container can still hold an unsuitable codec
the MP4 is just packaging - it can hold several different video codecs. An editing codec (ProRes, DNxHR) or an unusual encoder setting inside an otherwise-accepted the MP4 can still be rejected even though the extension is right.
- The export itself is incomplete or corrupted
An interrupted export, a killed app, or a file copied while still writing can look fine in a file browser but fail to open or upload anywhere. Re-export from the original source rather than re-trying the same file.
Fix it
- Re-export from your editor
Export a copy using codecs documented for the intended player. This site’s format converter does not offer MP4-to-MP4 conversion.
- Re-export from the original source
Rather than repairing a suspect file, export a fresh copy from the camera roll or editor and try that instead.
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