S ≈ 1000 × R × t / 8
Convert WebM to MP3
Convert WebM audio to MP3 directly in your browser with local processing and no media upload to a server.
- Export
WEBM file
WEBMMP3
Drop your WEBM file here
Or choose it from your device.
Conversion runs locally in your browser with Bethemesh’s shared audio engine.
Converting audio…
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How does this tool work?
Extract and convert the audio from a WebM file to MP3 directly in your browser. This is useful when a WebM recording also contains video and you only want to keep the sound.
FFmpeg/WASM opens the WebM container, discards video for the output, then decodes the available audio stream before encoding it as MP3. The source audio may use codecs such as Opus or Vorbis. The result is a new MP3 audio file; any video track from the WebM is not retained. The picker expects a .webm filename. A WebM may be an audio capture or include video; processing requests audio-only output and does not export images. FFmpeg decodes its selected audio track and encodes MP3 at 192 kbit/s. A WebM with no decodable audio cannot become a valid recording. There is no multiple-track selector or subtitle extraction. Opus or Vorbis input undergoes another lossy encoding generation. Container metadata and timing markers are not guaranteed in the MP3. Keep the WebM if retaining the images or original timing relationships matters.
How to use this tool
Select the WebM capture
Choose the .webm containing the sound you need.
Encode sound only
Start conversion; video images are excluded from output.
Review the extracted track
Confirm the MP3 contains the expected speech or ambience.
Convert WebM to MP3 — Calculation reference
- S
- Estimated bytes, excluding tags and container
- R
- Bitrate in decimal kbit/s
- t
- Duration in seconds
Use cases
Audio from WebM video
Retrieve an audio version from a container that also holds images.
Recorded meeting
Prepare an MP3 listening copy of a decodable WebM capture.
Browser voice capture
Adapt an older WebM recording for an MP3 player.
Examples
A twenty-second browser capture
192,000 × 20 ÷ 8. Video images in the source are not included in the audio output estimate.
Input
20 s of audio, MP3 at 192 kbit/sResult
About 480,000 audio bytesA seven-minute capture
Size follows the duration of the audio actually decoded; output contains neither video nor subtitles.
Input
420 s at the same target bitrateResult
About 10,080,000 bytesTips and best practices
- Keep WebM to reuse its video or subtitles.
- An interrupted capture may be incomplete and fail decoding.
- Source video size does not predict extracted MP3 size.
Sources and references
- FFmpeg project, FFmpeg Formats Documentation (opens in a new tab)Page in English
- FFmpeg project, FFmpeg Codecs Documentation (opens in a new tab)Page in English
Frequently asked questions
Are WebM subtitles recovered?
Output is MP3 sound, without subtitle or video-image export.
Can I choose a language from several WebM tracks?
There is no track selector on this surface. The chosen track follows FFmpeg’s automatic selection.
Does Opus remain untouched inside MP3?
No. Any Opus stream is decoded and then lossy-encoded as MP3 rather than simply rewrapped.
Can I keep video inside the MP3?
No. This output contains audio only and excludes video streams. Keep the WebM to retain images or their synchronization.
Why does my WebM fail to produce an MP3?
It may contain no decodable audio, be incomplete or use an unsupported combination. A WebM extension does not guarantee usable sound.
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