Upload problems
Video won't upload to X? Limits, format and a fix that works
Short answer
X fails uploads for three reasons: the file is over the account's limit (non-Premium: 140 seconds and 512 MB), the format is not supported (X says it will prompt you), or the connection or app is the problem. Re-export an MP4 with H.264 video and AAC audio under the limits, test on Wi-Fi, and try the web composer if the app keeps failing.
Key takeaways
- X Help: non-Premium accounts can upload up to 140 seconds and 512 MB.
- Premium subscribers can upload shorter than 4 hours and up to 16 GB.
- X prompts you when a video is not in a supported format.
- H.264 and AAC in an MP4 file is the most compatible export.
Find your case
| What you see | What it usually means | Do this |
|---|---|---|
| Fails at once with a format prompt | Unsupported format or codec | Re-export as MP4 H.264 (step 2) |
| Fails after a long upload | File too large or connection dropped | Compress and use Wi-Fi (step 3) |
| Works on web, fails in the app | App or phone storage | Update the app and free space (step 4) |
| Over 2 minutes 20 seconds | Free account length limit | Trim or split (step 1) |
Fix it step by step
Check length and size
Non-Premium accounts: up to 140 seconds and 512 MB, as stated on X Help. Trim first if you are over.
Export a standard file
ffmpeg -i in.mov -c:v libx264 -pix_fmt yuv420p -c:a aac -b:a 128k -movflags +faststart out.mp4. X says it will prompt you if the format is not supported.Compress if you are near the size limit
Raise CRF by 2 to 3 until the file is clearly under 512 MB.
Try another route
Upload from the web composer on a computer, switch between Wi-Fi and mobile data, update the app and free phone storage.
Before you press Post
- Play the exported file from start to finish.
- Check size and length against the limits.
- Keep the original in case you need a new export.
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.
Frequently asked questions
Why can't I upload a video to X?
Most often the file is over 140 seconds or 512 MB on a non-Premium account, or it is in a format X does not support.
What video format does X accept?
X prompts you if the format is not supported; MP4 with H.264 video and AAC audio is the safest export.
How long can X videos be with Premium?
X Help says Premium subscribers can upload videos shorter than 4 hours with a maximum file size of 16 GB.
Sources
- X Help: Posting videos on X (official, checked 2026-10-06)
- FFmpeg Documentation: Automatic stream selection and -map (official, checked 2026-10-06)
Reviewed 2026-10-06. Steps not attributed to a source are general video practice or computed above.