The short version
- Use an up-to-date Chrome, Edge or Safari.
- iPhone videos that won't open are usually HEVC — try another browser or record in Most Compatible.
- Keep the tab open and visible while exporting.
- Very long or 4K projects need more memory — trim first and close other tabs.
A file won't open
- iPhone .MOV videos: usually recorded in HEVC (H.265), which some browsers can't decode. Try Chrome or Safari, or see our iPhone video guide.
- HEIC photos: only Safari opens them directly. Convert to JPEG, or set your iPhone to Most Compatible.
- Uncommon formats like AVI, some MKV files or professional camera codecs may not be supported by browsers at all. Convert them to MP4 (H.264) first.
- Damaged or incomplete files — for example, a download that didn't finish — won't open anywhere. Check that the file plays in your computer's own video player.
- Cloud files that haven't been downloaded yet (iCloud, OneDrive, Google Drive placeholders) need to be fully downloaded to your device first.
Black or frozen preview
- Sound but no picture means the browser can read the audio but not the video codec — see "A file won't open" above.
- Update your browser and graphics drivers; video decoding relies on them.
- Turn on hardware acceleration in your browser settings if it has been turned off.
- Reload the page if the preview freezes after a long session — then add your clips again.
No sound
- Check the clip's volume in the Clip tab and the music volume in the Audio tab.
- Check your device: system volume, the silent switch on phones and the browser tab isn't muted.
- Browsers block sound until you interact with the page — press play once.
- The original has no audio: screen recordings and some app exports have none. Add music or a voiceover — see our voiceover guide.
Slow or stuck export
VDOAPP renders exports in real time on your own device, so a 3-minute video takes roughly 3 minutes to export. To keep it running smoothly:
- Keep the tab open and visible — browsers slow down background tabs, which can stall the export.
- Keep the device awake and plugged in for longer exports; don't let a phone lock its screen.
- Close other heavy tabs and apps to free memory and processing power.
- Split very long projects into parts if your device struggles.
Export format
Exports are saved as MP4 when your browser can record MP4, and as WebM otherwise. WebM plays in modern browsers and uploads to YouTube, but some apps prefer MP4. If you need MP4 and got WebM, try exporting in a recent Chrome, Edge or Safari. Our formats guide explains the difference.
Large files and older devices
- Trim before adding effects — shorter projects use less memory.
- 4K, high-frame-rate and HDR clips are demanding; older computers and phones may play them choppily in the preview even if the export is fine.
- Many long clips at once can exhaust memory on phones. Work in sections and join the results.
- Private browsing may limit memory or storage on some browsers — try a normal window.
Still stuck?
Try a different browser, restart your device and test with a short, simple clip to find out whether the problem is the file or the device. If it still doesn't work, contact us with your browser, device and the file type, and we'll take a look.
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