MP4 to WebM Converter
Convert MP4 to WebM with VP9 video and Opus sound for websites, HTML5 video players and web apps. Choose the quality and size; everything is encoded in your browser, so your video is never uploaded.
- Free
- No upload
- No watermark
Files
Settings for all files
Options · Same quality · Original size · Sound on
More options
GIFs can be up to 60 s long (30 s on phones). Use Trim (⋯ on a file) to pick a part.
Same copies AAC sound without re-encoding when the file already has it.
16-bit PCM, the format CDs and every audio editor use.
Add files to see what will happen to each one.
Add files to convert
Runs in your browser. Engine: mp4box.js (BSD-3-Clause), mp4-muxer and webm-muxer (MIT), gifenc (MIT), LAME via lamejs (LGPL-3.0, GPL-3.0) – licenses.
What works in your browser
Everything runs on your device, so what you can create depends on the browser. The last column is checked live in the browser you are using now and always wins over the table.
| Output | Chrome / Edge | Chrome Android | Firefox 130+ | Safari 16.4–18 | Safari 26+ | This browser |
|---|---|---|---|---|---|---|
| MP4 (instant copy) | Yes | Yes | Yes | Yes | Yes | Yes |
| MP4 (re-encode, H.264) | Yes | Yes | Yes, sound as Opus | Yes, AAC sound copied only | Yes | – |
| MOV | Yes | Yes | Copies only | Yes, AAC sound copied only | Yes | – |
| WebM (VP9 + Opus) | Yes | Yes (slow) | Yes | Checked live | Checked live | – |
| GIF | Yes | Yes | Yes | Yes | Yes | – |
| MP3 | Yes | Yes | Yes | Yes, long files limited | Yes | – |
| M4A | Yes | Varies by device | Copies only | Copies only | Yes | – |
| WAV | Yes | Yes | Yes | Yes, long files limited | Yes | – |
| Opus | Yes | Yes | Yes | Copies only | Checked live | – |
Instant copies work in every browser. Without WebCodecs (older browsers) re-encoding is not available, but MP3 and WAV files can still be made.
How to convert MP4 to WebM
- Add your MP4 or MOV videos.
- WebM is selected. Choose a resolution – 1080p or 720p is plenty for most websites – and the quality.
- Press Convert and keep the tab open; VP9 encoding takes longer than H.264, and the time left is shown on each file.
- Download the WebM and use it in a <video> element, next to an MP4 version for older browsers.
WebM for the web
VP9 with VP8 fallback
The best encoder this browser offers is picked automatically, with a level that matches the size and frame rate of your video.
Opus sound
Opus at 48 kHz gives clear sound at low bitrates, ideal for web pages where every kilobyte counts.
Right way up
Portrait and rotated phone videos are turned upright in the picture itself, so no player shows them sideways.
Frequently asked questions
Is MP4 to WebM free, and does my video stay private?
It is free to use as often as you like. The encoding happens inside your browser tab, so the MP4 is never uploaded and the WebM is created directly on your computer or phone.
Does MP4 to WebM lose quality?
Every WebM made from H.264 is a re-encode, so it is not bit-identical, but VP9 at "Same quality" looks like the original while usually being smaller. Lower settings are visibly softer; try a short clip first if quality is critical.
Why is VP9 encoding slow on my phone?
Few phones have a hardware VP9 encoder, so the work is done in software on the processor. The converter switches to a faster real-time mode on phones, but a computer is still several times quicker for long videos.
How long does it take to make a WebM?
At 720p a typical laptop encodes VP9 at a bit more than half of real time, so a 4-minute clip takes about 7 minutes, and longer at higher resolutions. Short clips for websites are usually done in under a minute.
Which browsers can create WebM?
Chrome, Edge and Firefox encode VP9 or VP8 with Opus. Safari's support varies by version and is checked live in the table above; if it cannot encode WebM, the tile is marked and MP4 is the better choice.
What happens to quality
WebM is the open video format of the web. Zebra Convert encodes the video as VP9, which needs about a third less data than H.264 for the same quality, and falls back to VP8 in browsers without a VP9 encoder. The sound becomes Opus at 48 kHz, the most efficient common audio codec. "Same quality" aims to look like the original; "Smaller file" is useful for background videos on websites.
MP4 and MOV files store rotation as a flag that some WebM players ignore, so portrait videos are rotated in the pixels and show up the right way everywhere. VP9 encoding is demanding: on phones it runs in a faster real-time mode and can still be slow, so for long videos a computer is the better choice. An MP4 that already holds VP9 or AV1 video is copied instead of re-encoded.