WebM to MP3 Converter

How to convert WebM to MP3

1. Drop the WebM file into the box above.
2. Choose the MP3 quality. Screen and call recordings are speech, so 128 kbps is usually enough.
3. Convert and download the MP3.

Where WebM files come from

When a website records your camera, microphone or screen, it usually uses the browser's built-in recorder, and Chrome, Edge and Firefox save that as WebM. Browser-based screen recorders, online voice recorders and some meeting tools hand you WebM files for the same reason. The format is open and efficient: the picture is VP8, VP9 or AV1 and the sound is Opus or Vorbis.

Audio-only WebM

A WebM can contain only sound, for example from an online voice recorder. Those convert exactly the same way; the tool simply finds no picture. Since the sound is decoded and the picture never is, video and audio-only WebM files convert at the same speed for the same length.

Why not convert the whole video?

You can: the WebM to MP4 converter makes a video that plays everywhere. That conversion has to re-encode the picture, though, which is slow in a browser. If you only need the sound of a lecture or meeting, converting to MP3 is much faster and gives a far smaller file.

Opus quality and bitrate

Opus already sounds good at low bitrates, so a speech recording rarely gains anything from a high MP3 bitrate, and converting cannot add detail that Opus discarded. 128 kbps is a good match. If you need the recording in the smallest possible size, the audio compressor can go down to 32 kbps mono. The Opus codec explainer covers why the codec sounds good at low bitrates.

Transcribe the recording

mydubly reads WebM directly, so for a transcript you can upload the original on the WebM to text page; the MP3 works too.

How the free converter works

The converter is ffmpeg, the open-source media toolkit, compiled to WebAssembly so it runs inside your browser tab. Your file is read straight from your disk by that engine; it is never uploaded to mydubly or anywhere else, and no account is needed.

• The engine is about 30 MB and downloads the first time you convert something. After that your browser normally keeps it.
• Large inputs are fine because the file is read in place, but the result is built in memory, so outputs are capped at about 1.5 GB.
• Speed depends on your device. Copying streams takes seconds; re-encoding video is the slow case.
• Keep the tab open until the download button appears. Closing it stops the conversion.