# WebM to MP4 that plays everywhere

For screen and camera recordings made in a browser and other VP8 or VP9 videos. Re-encoded to H.264 and AAC on your device. Free, no sign-up.

Your file never leaves your device: the tool runs inside your browser. Up to 1 GB. Use it at https://opusmotion.com/tools/webm-to-mp4.

## How to use it

1. Drop the WebM, or tap the box to pick it.
2. The converter re-encodes VP8 or VP9 to H.264 and Opus or Vorbis to AAC, on your device.
3. Download the MP4, or put the clip in a launch template.

The first time, your browser downloads the video engine (31 MB, once); after that it opens from the cache.

## About WebM files

WebM is the web's open video format: VP8, VP9 or AV1 video with Opus or Vorbis sound. Many screen and camera recorders that run in a browser save WebM, and so do some sites you download videos from.

Those codecs don't play in every MP4 player, so a WebM is always re-encoded here: to H.264 video and AAC sound, the pair that plays on phones, computers, editors and social apps.

Re-encoding happens on your device. It takes longer than a copy, and longer on a phone than on a computer; the bar shows how far along it is.

WebM files recorded in a browser often don't store their total length, so some players can't show a duration or let you skip ahead. The MP4 has both. AV1 WebMs can't be read here yet.

## Questions

### Why does a WebM have to be re-encoded?

Because MP4 players expect H.264 (or HEVC) video and AAC sound, and a WebM holds VP8 or VP9 with Opus or Vorbis. The picture has to be encoded again in the codec players read.

### How long does it take?

About as long as encoding a video takes on your device: a short screen recording takes seconds on a recent computer, a long one or a phone takes longer. Nothing leaves your device while it works.

### My WebM shows no duration. Will the MP4?

Yes. Recordings made in a browser often leave the length out of the WebM, which breaks the time bar in some players. The MP4 is written with its full length and plays and seeks normally.

### Does it work with AV1 WebMs?

Not yet: the video engine this tool uses can't read AV1. VP8 and VP9 WebMs, the most common, work.

### Is my video uploaded anywhere?

No. The conversion runs inside your browser, with ffmpeg compiled to WebAssembly. Your file is read where it is and never sent to a server. The first time, your browser downloads the video engine (31 MB, once); after that it opens from the cache.

### What's the largest file it takes?

Up to 1 GB when the video is copied. When it needs re-encoding: up to 500 MB and 2 minutes on a computer, or 200 MB and 1 minute on a phone or low-memory device. The limit is decided after reading the codecs. The MP4 is kept in your browser's memory until you download it, so a phone, which has less memory, may not manage a very large file: if one fails there, try it on a computer.

## More free tools

- [Video converter](https://opusmotion.com/tools/video-converter.md): Any video to MP4: MOV, WebM, MKV, AVI and more, copied without re-encoding when it can be
- [MOV to MP4](https://opusmotion.com/tools/mov-to-mp4.md): iPhone videos, Mac screen recordings and QuickTime files to MP4, usually in seconds
- [MKV to MP4](https://opusmotion.com/tools/mkv-to-mp4.md): OBS and other MKV recordings to MP4, remuxed in seconds when they hold H.264
- [All free tools](https://opusmotion.com/tools.md)