# Convert MP4 to WebM

> Convert MP4 to WebM online free: phone and camera videos become small VP9 WebM files for websites. Many at once, nothing is uploaded. No sign-up, no watermark.

URL: https://nibbo.org/en/mp4-to-webm/

## MP4

MP4 is what phones, cameras and most apps record and share: almost always H.264 or HEVC video with AAC sound.

An MP4 plays nearly everywhere, but websites and some tools want a smaller WebM, an animated GIF or just the sound as MP3.

## MP4 to WebM: remux or re-encode

MP4 to WebM is always a re-encode: WebM holds VP9 (or VP8, AV1), not the H.264 or HEVC inside the MP4. Your browser’s VP9 encoder does the work, the sound becomes Opus.

At the Original preset a 1080p minute becomes about 45 MB of VP9, usually less than a phone’s MP4. VP9 encoding is slower than playing the video; a 4K clip takes several times its length.

## How it works

1. Drop one or more MP4 files: WebM is already selected. Quality, maximum resolution and sound can be changed before you start.
2. Streams that fit WebM are copied; anything else is re-encoded with WebCodecs, or FFmpeg compiled to WebAssembly when the browser can’t.
3. Download each file, or all of them as one ZIP.

## Questions

### Are my videos uploaded?

No. Reading, remuxing and encoding all run in this browser tab. Open DevTools and watch the Network tab while a file converts: no request carries it.

### Why is one file done in seconds and another takes minutes?

A remux only copies the streams, so it runs at disk speed. A re-encode decodes and encodes every frame; FFmpeg in WebAssembly, used when the browser can’t, is slower still.

### How large can a video be?

Up to 3 GB per file for free, and as many files as you like. Remuxes and WebCodecs re-encodes stream from the disk; the FFmpeg path holds the result in memory.

## Related

### Convert video

- [Video converter](https://nibbo.org/en/video-converter/)
- [Convert MOV to MP4](https://nibbo.org/en/mov-to-mp4/)
- [Convert MKV to MP4](https://nibbo.org/en/mkv-to-mp4/)
- [Convert AVI to MP4](https://nibbo.org/en/avi-to-mp4/)
- [Convert WebM to MP4](https://nibbo.org/en/webm-to-mp4/)
- [Convert WMV to MP4](https://nibbo.org/en/wmv-to-mp4/)
- [Convert FLV to MP4](https://nibbo.org/en/flv-to-mp4/)
- [Convert 3GP to MP4](https://nibbo.org/en/3gp-to-mp4/)
- [Convert M4V to MP4](https://nibbo.org/en/m4v-to-mp4/)
- [Convert MTS to MP4](https://nibbo.org/en/mts-to-mp4/)
- [Convert MOV to WebM](https://nibbo.org/en/mov-to-webm/)
- [Convert MOV to GIF](https://nibbo.org/en/mov-to-gif/)
- [Convert WebM to GIF](https://nibbo.org/en/webm-to-gif/)
- [Convert MOV to MP3](https://nibbo.org/en/mov-to-mp3/)
- [Convert WebM to MP3](https://nibbo.org/en/webm-to-mp3/)
- [Convert MKV to MP3](https://nibbo.org/en/mkv-to-mp3/)
- [Convert AVI to MP3](https://nibbo.org/en/avi-to-mp3/)
- [MP4 to MP3](https://nibbo.org/en/mp4-to-mp3/)

### Compress video

- [Compress video to a target size](https://nibbo.org/en/compress-video/)
- [Compress MP4 video](https://nibbo.org/en/compress-mp4/)
- [Compress WebM video](https://nibbo.org/en/compress-webm/)

### More tools

- [Compress image to an exact size](https://nibbo.org/en/compress-image/)
- [Compress PDF](https://nibbo.org/en/compress-pdf/)
- [Audio converter](https://nibbo.org/en/audio-converter/)