MP4MPEG-4 Part 14
The most compatible video format, played by almost every phone, computer, TV and social network.
Convert MP4 to WebM
Turn your MP4 videos into WebM videos right in your browser, so your files are never uploaded to a server. How long it takes depends on the video’s length and your device.
- Files never uploaded
- Free, no sign-up
- No queue
MP40000002066747970
WEBM1A45DFA39F428681
The first bytes of a file often reveal its real format.
or drop them here. You can also paste an image (Ctrl+V).
Free · No sign-up · No upload
Files
These sample files are generated on the page. Convert them to try it out, or add your own.
How to convert MP4 to WebM
- 01
Add your MP4 files
Click “Choose MP4 files” or drop them on the page. You can add several at once.
- 02
Check the WebM format
WebM is already selected. You can lower the video resolution: 1080p, 720p or 480p.
- 03
Convert and download
Click “Convert”, then download your WebM file. With several files, grab everything at once as a ZIP.
MP4 to WebM: what to know
WebM is mainly used on the web: background videos, demos embedded in a page, platforms that favour open formats. It accepts neither the H.264 nor the AAC of a typical MP4, so everything is re-encoded. The picture becomes VP9, or AV1 or VP8 depending on what your browser can do, and the sound becomes Opus at 128 kbps. The video bitrate is worked out automatically from the resolution.
Because every frame is recalculated, the conversion takes much longer than a simple change of container, and each re-encode costs a little quality, so keep the original MP4. Vertical phone videos stay the right way up, as the rotation is applied to the picture itself. If your browser lacks WebCodecs, the page records the video in real time instead: keep the tab open for its whole length.
MP4 vs WebM: what’s the difference?
WEBMWebM
An open video format designed by Google for the web (VP8, VP9 or AV1). It is light, but some apps, TVs and phones cannot play it.
MP4 to WebM: frequently asked questions
How do I offer a WebM video on my website with an MP4 fallback?
In your page’s video element, list two sources: the WebM first, with the type video/webm, then the original MP4, with the type video/mp4. The browser uses the first one it can play, and devices that ignore WebM fall back to the MP4. So keep both files online.
Will the WebM always be smaller than my MP4?
Not necessarily. The WebM’s bitrate is set from the resolution, around 3.6 Mbps at 1080p with VP9. A phone video recorded at a high bitrate therefore shrinks a lot, while an MP4 already optimised for the web gains little and may even grow. Choosing 720p or 480p cuts the size further.
Are my MP4 files uploaded to the internet?
No. The file is read and converted by your browser, on your device. Nothing is sent to a server, and nothing is kept after you close the page.
Does converting MP4 to WebM reduce quality?
When possible, the video is simply moved into the new container without re-encoding, so nothing is lost. Otherwise your browser re-encodes it at high quality.
How many MP4 files can I convert?
As many as you like, for free and without signing up. Add them all, then download the results one by one or in a single ZIP. The maximum size depends on your device and browser, with a few caps that protect its memory (for example 20,000 files per archive or 5 million filled cells per workbook: see the home page FAQ); a file over one of them is not converted, and a message says so.
Does it work on iPhone and Android?
Video conversion uses WebCodecs, a feature of recent versions of Chrome, Edge, Safari and Firefox (except Firefox for Android, which does not have it yet); a video whose picture or sound the browser cannot read or write is refused with a message that says so. On a phone, stick to videos of a few minutes.