Free tool
WebM to MP3 converter
Drop a WebM file, such as a browser recording or a video saved from the web, to convert WebM to MP3 here: the page decodes its Opus or Vorbis sound and writes an MP3 that plays on anything, all inside your browser.
- Free
- Works on phones
- Nothing is uploaded
Save as
MP3 quality
Plays everywhere. The sound is re-encoded at the quality you pick.
Drop your WebM file here, or Choose your WebM file
Any audio or video file, up to 1 GB and 2 hours. It’s converted in your browser; nothing is uploaded.
MP3 encoding by LAME, open-source software.
Recorded a call or a talk in the browser? NoteOwl doesn’t open WebM, but it imports the MP3 you make here and transcribes it on your Mac, labelling each speaker.
How it works
How do you convert WebM to MP3?
Leave MP3 selected and drop the WebM. Your browser decodes the Opus or Vorbis sound, passing over any picture, and the page’s own MP3 encoder writes the file at the bitrate you chose. A five-minute WebM video took 3.1 seconds in Chrome at 192 kbps. Play it, then download.
- 1
Pick 128, 192 or 320 kbps
128 kbps is plenty for a voice memo or a screen recording with narration; choose 192 or 320 kbps when the WebM holds music.
- 2
Add the WebM
Audio-only or with video, from any recorder or website. A WebM saved with an .ogg ending opens too, because the file is recognised by what is inside.
- 3
Download the MP3
Listen to the opening seconds, then save it. It keeps the WebM’s name with .mp3 on the end.
How big is the MP3, compared with the WebM?
Bigger than the sound it came from. Opus stores sound in far fewer bits than MP3 needs, so a one-minute audio-only WebM of 0.22 MB became a 0.96 MB MP3 at 128 kbps. An MP3’s size is set by its bitrate: 1.44 MB a minute at 192 kbps.
- Audio only, 1 min (Opus, mono)
- Its size0.22 MB
- MP3 out128 kbps: 0.96 MB
- Took (Chrome / WebKit)0.66 s / 0.58 s
- Video, 1 min (VP9 + Opus, stereo)
- Its size0.89 MB
- MP3 out192 kbps: 1.44 MB
- Took (Chrome / WebKit)0.6 s / 0.8 s
- Video, 5 min (VP9 + Opus, stereo)
- Its size4.43 MB
- MP3 out128 kbps: 4.8 MB
- Took (Chrome / WebKit)3.5 s / 3.7 s
- The same 5-minute video
- Its size4.43 MB
- MP3 out192 kbps: 7.2 MB
- Took (Chrome / WebKit)3.1 s / 3.7 s
| WebM in | Its size | MP3 out | Took (Chrome / WebKit) |
|---|---|---|---|
| Audio only, 1 min (Opus, mono) | 0.22 MB | 128 kbps: 0.96 MB | 0.66 s / 0.58 s |
| Video, 1 min (VP9 + Opus, stereo) | 0.89 MB | 192 kbps: 1.44 MB | 0.6 s / 0.8 s |
| Video, 5 min (VP9 + Opus, stereo) | 4.43 MB | 128 kbps: 4.8 MB | 3.5 s / 3.7 s |
| The same 5-minute video | 4.43 MB | 192 kbps: 7.2 MB | 3.1 s / 3.7 s |
What is a WebM file, and where do they come from?
WebM is an open audio and video format from Google, built on Matroska: Opus or Vorbis sound, and VP8, VP9 or AV1 pictures. You meet it as a browser recording, from voice and screen recorders that run in a web page or an extension, and in videos saved from websites.
Such recorders usually rely on the browser’s built-in recorder, which in Chrome and Firefox can write WebM with Opus sound. OBS is different: its usual formats are MKV and MP4, and it writes WebM only through its custom FFmpeg output. Every one of them converts here, and video to MP3 covers the other kinds of video.
- A voice recorder in a web page
- What is usually insideSound only, as Opus
- A screen recorder in a tab or an extension
- What is usually insideVP8 or VP9 picture with Opus sound
- A video saved from a website
- What is usually insideVP9 picture with Opus sound
- An older WebM, from before Opus
- What is usually insideVP8 picture with Vorbis sound
| Where the WebM came from | What is usually inside |
|---|---|
| A voice recorder in a web page | Sound only, as Opus |
| A screen recorder in a tab or an extension | VP8 or VP9 picture with Opus sound |
| A video saved from a website | VP9 picture with Opus sound |
| An older WebM, from before Opus | VP8 picture with Vorbis sound |
Why turn a WebM into an MP3?
Because MP3 plays nearly everywhere and WebM does not: car stereos, MP3 players, audio editors and upload forms for sound files often take MP3 but not WebM. Saving only the sound also leaves the picture behind; for a recorded call or lecture, the sound is all you need.
If you are about to record your own voice, NoteOwl’s voice recorder saves an MP3 or a WAV directly, so there is no WebM to convert afterwards.
Does the sound change when Opus becomes MP3?
A little. The Opus is decoded and encoded again as MP3, and nothing restores what the Opus encoder left out. Speech comes through cleanly at 128 kbps; give music 192 or 320 kbps. Opus decodes at 48 kHz, so the MP3 is 48 kHz unless you untick the rate box.
Mono recordings stay mono and stereo ones stay stereo. With the box unticked the MP3 is written at 44.1 kHz, the rate of CD audio, for players or projects that expect it.
Can NoteOwl transcribe a browser recording?
Yes, once it is an MP3. NoteOwl doesn’t open WebM, so convert the file here first; then NoteOwl imports the MP3 on your Mac, transcribes it with on-device AI models, labels each speaker and keeps the transcript searchable next to everything else you have recorded.
For meetings still ahead, NoteOwl can take the notes itself on the Mac, without adding a bot to the call, and there is nothing to convert afterwards.
FAQ
Questions about converting WebM to MP3
Is the WebM uploaded to convert it?
No. The file is read from your device and its sound becomes an MP3 inside the browser tab; no request leaves the page while it works. A recorded call or a screen recording stays on your computer, and no account is needed.
Can it convert a WebM that has no video?
Yes. Audio-only WebM files, the kind web voice recorders save, convert the same way as WebM videos. A one-minute mono Opus recording became an MP3 in 0.66 seconds in Chrome.
Does it read WebM files with Vorbis sound?
Yes. Vorbis was WebM’s original sound format before Opus, and the converter reads both, so an older WebM gives an MP3 the same way. The picture is never decoded, so its format makes no difference.
Why is the MP3 bigger than the WebM I started with?
Because Opus, the usual sound format in WebM, needs far fewer bits than MP3 for the same sound. A one-minute audio-only WebM of 0.22 MB became a 0.96 MB MP3 at 128 kbps, about four and a half times larger. 128 kbps gives the smallest MP3 the converter makes.
Which bitrate suits a screen recording?
If the sound is someone talking through what is on screen, 128 kbps keeps the voice clear at about 0.96 MB a minute. Pick 192 or 320 kbps only when the recording is mostly music or game sound you want to keep in detail.
How long a WebM can it convert?
Files up to 2 hours long and 1 GB in size. Only the sound is decoded, so a five-minute WebM video took about 3 seconds in Chrome on an Apple M1 Pro.
Keep exploring
More audio converters
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- MP3 to M4A converterConvert MP3 to M4A (AAC) in your browser at 96, 128 or 192 kbps, for iPhone, iPad and Mac apps; nothing is uploaded
- AAC to MP3 converterConvert raw .aac files (ADTS), from radio recorders, Android apps and stream rips, to MP3 in your browser; nothing is uploaded
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- Online voice recorderRecord your voice in the browser with a level meter, timer and pause, play it back, and save it as MP3 or WAV; nothing is uploaded
- Video to textTurn video to text free: drop in an MP4, MOV, M4V, MKV or WebM video and get an AI transcript with times, as text, SRT, VTT or Word; only the sound is sent, nothing is stored
- Video to MP3 converterTurn any video’s sound into an MP3 in your browser: MP4, MOV, MKV, WebM and 3GP, at 128, 192 or 320 kbps; nothing is uploaded
Browser recordings into searchable notes, on your Mac
Free to download. Runs entirely on your Mac.
macOS 26 or later · Apple Silicon (M1 or newer) · 16 GB memory minimum, 24 GB recommended
About NoteOwl
NoteOwl is private AI meeting notes and memory for the Mac. It captures meetings without a bot joining the call, labels every speaker, writes summaries and action items, and builds a memory of every conversation that you can chat with — fully offline, because the speech recognition and the AI run on the Mac itself. Dictation into any app is free; Pro is a one-time purchase.
NoteOwl pricing: what’s free and what Pro adds
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