MP4 to MP3 converter
Choose an MP4, pick the MP3 quality and save the sound as an MP3. It runs in your browser and the file is never uploaded.
Free · no signup Runs in your browser
How do I convert MP4 to MP3?
Choose the MP4 file, pick an MP3 quality and download the result. An MP4 is a container that holds video and sound together; the tool decodes the sound track with your browser and saves it as an MP3. The conversion happens on your device, so the MP4 is never uploaded.
MP4 is a container, MP3 is the sound
People often think of MP4 as a video format, but it is really a container: a wrapper that can hold a video track, one or more sound tracks and subtitles. The sound inside an MP4 is usually AAC. An MP3 is a different, older sound format. Converting MP4 to MP3 means taking the sound track out, decoding it and encoding it again as MP3.
Because the sound is re-encoded, the result is a copy of the original sound at the quality you choose, with a little loss. A higher bit rate keeps more detail but makes a bigger file. For speech a bit rate of 128 kbit/s is plenty, and mono halves the size again. For music, 192 or 256 kbit/s is a good balance.
It runs in your browser. Your video is never uploaded, and there is no watermark or sign-up. MP3 encoding uses LAME (lame.sourceforge.io), an open-source encoder, licensed under the LGPL.
How it works in detail
An MP4 is a container that holds video and sound together. The tool reads the file on your device and your browser decodes its sound track, which is almost always AAC. The sound is then encoded as MP3 with LAME at the bit rate you choose (128, 192, 256 or 320 kbit/s), and the MP3 is offered for download. The MP3 has the same length as the video. The size in kilobytes is the bit rate ÷ 8 × seconds, about 1 MB a minute at 128 kbit/s. Metadata such as chapters and cover art is not copied. 'Make it mono' saves space for speech. Nothing is uploaded, so a private recording stays on your device.
How to use it
- Choose the MP4 file.
- Pick the MP3 quality, and tick mono if the sound is speech.
- Wait while the sound is decoded and encoded.
- Check the length and size shown.
- Download the MP3.
What changes and what stays the same
What the tool does to your file, and what it leaves alone.
| Aspect | What happens |
|---|---|
| Video | Dropped: only the sound is kept |
| Sound | Encoded as MP3 at the bit rate you choose |
| Length | The same as the video |
| Chapters and cover art | Not copied |
| MP3 quality | MP3 is lossy: each save as MP3 costs a little detail, so keep your original |
| Privacy | Your file is read on your device and is not uploaded; there is no account and no watermark |
When to use it
- Saving the audio of a recorded meeting or lecture
- Making a music file from a music video you own
- Creating a small file for an audio-only player
- Preparing sound for a transcription tool
Problems you may run into
Most problems come from the file itself, not from the tool.
| What you see | Likely cause | What to do |
|---|---|---|
| There is no sound | The video has no audio track, or the browser cannot decode it | Check that the video plays with sound in your browser |
| The file is large | A long video at a high bit rate | Use 128 kbit/s, or mono for speech |
| The result is slow | Decoding and encoding run on your device | Use a computer, and keep the tab open |
| Quality is lower than the video's sound | MP3 is lossy | Choose 256 or 320 kbit/s |
| The file will not open | Your browser cannot decode this format, or the file is damaged | Try Chrome, Edge or Firefox on a computer, or open the file elsewhere to check that it plays |
| The browser slows down or stops | A very large file is processed on your own device | Close other tabs, try a computer, or use a smaller file |
Mistakes it helps you avoid
- Converting copyrighted video you have no right to copy.
- Expecting the video picture to come along: MP3 is sound only.
- Choosing a very low bit rate for music.
- Closing the tab while it is working.
How it works
Your file is decoded and re-encoded inside your browser.
1. The MP4 is read on your device and its sound track is decoded by your browser.2. The sound is encoded as MP3 with LAME at the bit rate you choose.3. The MP3 is offered as a download. Nothing is uploaded.
The tool uses your browser's decoder, so it handles the MP4 sound formats the browser can play (almost always AAC). Size in kilobytes is bit rate ÷ 8 × seconds. The MP3 has the same length as the video. Metadata such as chapters and cover art is not copied.
Example: a 4-minute music video
You convert a 4-minute MP4 music video at 256 kbit/s.
- Bit rate256 kbit/s
- Size256 ÷ 8 × 240 = 7,680 KB
An MP3 of about 7.5 MB
At 128 kbit/s it would be half that.
Terms on this page
- Container
- A file format that wraps video, sound and other tracks together, such as MP4.
- AAC
- The sound format usually found inside MP4 files.
Common questions
Can I convert MP4 to MP3 without losing quality?
MP3 is lossy, so there is a small loss. A higher bit rate such as 256 or 320 kbit/s keeps more detail.
Does the MP3 keep the video's picture?
No. MP3 is sound only.
Is my file uploaded?
No. Your browser reads and converts the file on your own device. Nothing is sent over the network.
Why will my MP4 not convert?
The sound format may not be supported by your browser, or the file may be damaged. Try Chrome, Edge or Firefox.
Can I convert several MP4 files at once?
Yes. Add several files and download each MP3, or use Download all.
Where these numbers come from
- MDN Web Docs — BaseAudioContext.decodeAudioData() How a browser decodes an audio or video file's sound into samples.
- LAME MP3 encoder (lame.sourceforge.io), LGPL The MP3 encoder, here a JavaScript port (lamejs) used unmodified as a separate file.
- MDN Web Docs — Web audio codec guide Which audio formats browsers can play and decode.
- MDN Web Docs — Using files from web applications How a page reads a file you choose without uploading it.
Last verified 2026-10-25 The method on this page is checked against the sources above at least once a year. Spotted something out of date? Tell us and we will fix it.
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