About this WebM to MP4 tool
WebM uses VP8 or VP9 video and Opus audio. Those are great on the web but not every app can open them, especially older editors, iPhones and messaging apps.
The tool decodes the WebM and re-encodes it as H.264 MP4 using your device's encoder. A 5-minute 1080p recording usually takes a minute or two on a modern computer.
How to use WebM to MP4
- Choose or drop the WebM file.
- Click Convert video and wait for encoding to finish.
- Download your MP4.
Features
Plays everywhere
H.264 MP4 output.
Keeps sound
Opus audio becomes AAC.
High quality
Uses high-quality encoder settings.
Private
Nothing leaves your device.
Good to know
- Works in up-to-date Chrome, Edge, Firefox and Safari on computers and Android. iPhones with iOS 17 or newer work too.
- Files up to about 1 GB work well on most computers. Phones handle shorter clips best.
- Only edit videos you own or have permission to use.
Frequently asked questions
Why does WebM to MP4 take longer than MOV to MP4?
WebM uses different codecs, so the picture has to be re-encoded rather than copied.
Will the MP4 work in WhatsApp and iPhone?
Yes. The output uses H.264 and AAC, which every phone supports.
Can I convert an MKV file here?
Yes, MKV files are accepted too.
Is my video uploaded?
No. The whole job runs inside your browser using your device's built-in video encoder, so the video never leaves your device.