Formatomat
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Convert WebM to MP4

Turn your WebM videos into MP4 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

or drop them here. You can also paste an image (Ctrl+V).

Free · No sign-up · No upload

How to convert WebM to MP4

  1. 01

    Add your WebM files

    Click “Choose WebM files” or drop them on the page. You can add several at once.

  2. 02

    Check the MP4 format

    MP4 is already selected. You can lower the video resolution: 1080p, 720p or 480p.

  3. 03

    Convert and download

    Click “Convert”, then download your MP4 file. With several files, grab everything at once as a ZIP.

WebM to MP4: what to know

WebM files often come from an in-browser screen recorder, a video call or a download. Their picture (VP8, VP9 or AV1) and Opus sound go into an MP4 unchanged: they are copied without re-encoding, so without loss. Vorbis sound, which MP4 cannot hold, is re-encoded, as AAC when the browser can, otherwise as Opus; multichannel (5.1) sound is re-encoded in stereo when the browser cannot encode all its channels, and a message says so. It is quick, and the MP4 ends up roughly the same size as the WebM.

The MP4 is written with its index at the start of the file, so once online it can begin playing before the download finishes. In the rare cases where this copy fails, Formatomat switches to real-time recording: the conversion then takes as long as the video, the tab must stay open until the end, and the picture is re-encoded.

WebM vs MP4: 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.

MP4MPEG-4 Part 14

The most compatible video format, played by almost every phone, computer, TV and social network.

WebM to MP4: frequently asked questions

How do I get an H.264 MP4 from a WebM?

Under Size, choose a resolution lower than the video’s, for example 720p for a 1080p WebM. The picture is then re-encoded, as H.264 in most browsers, which takes longer than a copy. The sound, however, may stay Opus, which some older devices cannot play.

My WebM recording won’t seek properly: will the MP4 fix that?

Usually, yes. WebM files made in a browser often lack both their duration and the cue points that make skipping ahead possible. The MP4 is written with a complete index, so the duration shows up and the progress bar works. The picture, copied as it is, stays identical.

Are my WebM 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 WebM to MP4 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 WebM 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.