MP4 to MP3 Converter
Drop an MP4, get the audio as MP3. The whole thing runs in your browser — the file never leaves your device.
Drop your MP4 file here
Converts to .mp3 — stays on your device
Why convert MP4 to MP3?
- Pulling the audio out of a Zoom or Google Meet recording to send to an AI transcription service like Otter, Fireflies, or Whisper.
- Extracting lecture audio from a recorded MP4 for offline listening on an iPod, old car stereo, or running watch that only reads MP3.
- Saving the audio from a podcast episode delivered as an MP4 video file so it plays back in Apple Podcasts, Pocket Casts, or Overcast.
- Ripping interview audio from a recorded webinar or Teams call for a journalist's offline archive or a researcher's coding pass.
- Extracting speech tracks from MP4 gameplay recordings for a YouTube commentary edit in DaVinci Resolve or Premiere Pro.
- Turning a MP4 music video download into an audio-only MP3 for a car playlist, gym mix, or workout rotation.
How our converter works
Your MP4 is loaded into an in-browser WebAssembly build of ffmpeg. The audio track is extracted and re-encoded as 192 kbps MP3 — no video frames are touched, which is why this runs much faster than a full re-encode. Expect a few seconds for a 30-minute recording on a modern laptop. Nothing is uploaded: lectures, client interviews, medical dictations, and legal depositions stay on your device.
MP4 vs MP3 — what's the difference?
| Feature | MP4 | MP3 |
|---|---|---|
| Contents | Video + audio + metadata | Audio only |
| Typical size | Megabytes to gigabytes | About 1 MB per minute at 192 kbps |
| Playback devices | Video players, phones, smart TVs | Everything with a speaker — podcast apps, old MP3 players, car stereos |
| Editing | Video editors (Premiere, Resolve, Final Cut) | Audio editors (Audacity, Reaper, GarageBand) |
| Best for | Watching, sharing with visuals | Listening, transcription, podcasting |
Frequently asked questions
How long does it take to convert a 1-hour MP4?
Typically 10–30 seconds on a modern laptop. Audio extraction is much faster than full video re-encoding because ffmpeg doesn't need to decode every frame — it just pulls the existing audio stream and re-encodes it as MP3.
Is the audio quality preserved?
At 192 kbps CBR, the output is transparent for speech and very close to original for music. If you need lossless, extract to WAV or FLAC instead (coming soon).
What's the file size limit?
Practical limit is around 500 MB for the source MP4 — above that, browser memory starts failing. For multi-hour recordings, a desktop ffmpeg install handles bigger files more reliably.
Are my files uploaded?
No. The conversion runs entirely in your browser via WebAssembly. Files never touch a server — which is why lawyers, doctors, and researchers under NDA use this for privileged recordings.
Why does the first conversion take longer?
The ffmpeg WebAssembly module (about 30 MB) is downloaded on first use and cached. Subsequent conversions in the same session start instantly.
Does this work for .m4v or .mkv files?
This specific tool accepts .mp4. For .m4v you can rename to .mp4 (they're usually the same container). For .mkv, use the MKV to MP4 converter first, then extract audio.
About the MP4 format
MP4 (MPEG-4 Part 14) is the dominant video container of the streaming era — YouTube, Zoom, Teams, most phone cameras, and every social platform default to it. Inside, an MP4 usually holds an H.264 or H.265 video stream paired with an AAC audio stream, plus metadata. MP3 (MPEG-1 Audio Layer III) predates MP4 by a decade but refuses to retire: every audio app, every podcast host, every car stereo built since the early 2000s plays MP3 without question. Extracting the MP3 audio from an MP4 is one of the highest-volume file conversions on the internet, driven by the simple reality that voice content recorded as video is often more useful as audio.