WebM to MP3 converter

People holding a WebM who only want what was said or played in it. A Chromebook saves every screen recording as WebM, and so do most screen and voice recorders that run in a browser, so a recorded lecture, a meeting, a voice note or a narrated walkthrough often starts life this way. Others have a WebM from a download or a chat app and need an MP3 for a phone, a car, a podcast host or an editor that will not open WebM. Only convert sound you have the right to use.

WebM was made for the web, which is why recordings made on the web end up in it. The screen recorder built into every Chromebook saves WebM. Recorders that run in a browser tab, for the screen, a webcam or just a voice, usually do too, because WebM is what Chrome and Firefox record most readily. You will also meet WebM in downloads from video sites and in some chat and messaging apps.

The sound inside is almost always Opus. Older files, and some download tools, use Vorbis instead. The converter reads both, in Chrome, Edge, Firefox and Safari, and tells you which one your file has before you convert.

Opus is much more efficient than MP3. Speech in Opus can sound clear at 48 kbps, where MP3 needs far more bits for the same result. So when a WebM holds only sound, the MP3 usually comes out larger.

We converted a ten-minute voice recording, saved as 48 kbps mono Opus the way a browser recorder writes it: 3.5 MB. As an MP3 it was 9.6 MB at 128 kbps, 14.4 MB at 192 and 24.0 MB at 320, in four to six seconds in Chrome, Firefox and WebKit, the engine behind Safari, on an M1 Mac. None of the larger files sounds better than the 128 kbps one. When the sound in your file is that light, the converter says so and suggests 128 kbps.

With video in the file, the opposite happens: the picture is nearly all of the size, so taking it away shrinks the file a lot. A three-minute 720p screen recording with 128 kbps Opus sound came to 35.7 MB as a WebM. Its MP3 was 2.9 MB at 128 kbps, 4.3 MB at 192 and 7.2 MB at 320, in two to three seconds in each browser.

That makes an MP3 an easy way to send a recorded class or call by email or message. A one-hour lecture at 128 kbps is about 58 MB.

If what you are sending to can play WebM, send the WebM. Chrome, Firefox, Edge, Safari, VLC and YouTube all handle it, and the original sound is already better per megabyte than any MP3. For a voice recording the WebM is also the smaller file.

An MP3 will not fix the recording. A quiet microphone, echo, background noise or a Chromebook recording that captured only the microphone and not the computer’s sound all stay as they were; 320 kbps only makes a larger copy of the same problem. If the WebM has no sound at all, there is nothing to convert, and the converter says so. To keep the picture as well, use the WebM to MP4 converter instead.