MP4 to MP3 Converter
To convert MP4 to MP3 here, drop the video on the page: it decodes the soundtrack, encodes it as MP3 at 128, 192 or 320 kbps, and the video is never uploaded. The picture is ignored, and you can keep the whole soundtrack or only one section.
- Free
- No sign-up
- No watermark
- Runs in your browser
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What happens to the soundtrack of an MP4
An MP4 holds a picture and a soundtrack, and an MP3 holds only sound. This page reads the soundtrack and leaves the picture alone, so a 4K video is no harder to convert than a small one. What the page does to the sound depends on the codec it finds, the number of channels and the sample rate. The table lists the cases you are most likely to meet.
| In the MP4 | What the page does | What you get |
|---|---|---|
| AAC audio, which phones, screen recorders and many downloads write | Decodes it and encodes MP3 at the bitrate you choose | A second round of compression, so a higher bitrate keeps more detail |
| Audio that is already MP3 | Copies it when Keep original is chosen and the whole file is converted | The same audio with no loss |
| More than two channels, such as 5.1 surround | Mixes them down to stereo | A stereo MP3, because MP3 has no layout beyond stereo here |
| An unusual sample rate, such as 96 kHz | Converts it to 48 kHz | An MP3 at 48 kHz |
| No audio track at all, such as a silent screen recording | Stops with a message | No file, because there is no sound to extract |
| The picture | Never decodes it | Nothing of it in the MP3 |
An MP3 is as big as its bitrate times its length, divided by 8 to turn bits into bytes. A 3-minute music video comes to 2.88 MB at 128 kbps, 4.32 MB at 192 kbps and 7.2 MB at 320 kbps. A 45-minute lecture comes to 43.2, 64.8 and 108 MB, and a 2-hour film to 115.2, 172.8 and 288 MB. The page shows the estimate for your own file before you convert.
Why MP3 always means a second compression
The sound in an MP4 is usually AAC, which is already a lossy format. MP3 is a different codec, so the AAC cannot be copied into it. The page decodes the AAC and compresses it again as MP3, and that second pass loses a little more detail. Choosing 320 kbps, the highest bitrate the MP3 standard allows, keeps as much as possible, but it cannot bring back detail that AAC already dropped. The M4A format avoids the problem: its Keep original choice copies the AAC untouched when you convert the whole file.
The MP3 encoder arrives on your first conversion
No browser can encode MP3 by itself. The first time you convert, the page therefore downloads a small WebAssembly encoder, about 300 kB, and uses it from then on. It is program code, and no part of your file is in the download. You may see that request in your browser's network tool, and your video is not part of it.
Which browsers can convert an MP4 to MP3
The picture is never decoded, so the page needs only the audio half of WebCodecs: an audio decoder to read the AAC and an audio encoder for the MP3. Chrome and Edge 94 and newer have both, and Safari has had them since version 26. An older Safari shows a message when the page loads instead of starting and failing halfway through.
Questions people ask
How do I convert MP4 to MP3 for free?
Drop the MP4 on the box at the top of the page, leave the format on MP3 at 192 kbps or pick 128 or 320, and press Convert to MP3. The file plays on the page when it is ready, and the Download button saves it. Nothing is paid, no account is needed and no video is uploaded.
Which bitrate should I pick for MP4 to MP3?
192 kbps is the starting choice and suits most videos. 128 kbps is clear enough for speech and makes a file one third smaller. 320 kbps is the most the MP3 standard allows and is worth choosing for music. The AAC in the MP4 is already compressed, so a higher bitrate cannot bring back detail that is gone.
Why does the page say my MP4 has no audio track?
Some MP4 files hold only a picture, such as a screen recording made without a microphone. The page says the file has no audio track and makes no MP3, because there is no sound to extract. Choose a video that has sound, or record it again with the microphone on.
Can I convert a long MP4 to MP3?
Yes. The tool has no length limit of its own, and the MP4 is read from your disk in small pieces. The MP3 is built in memory, so the practical limit is free memory: a 2-hour film at 192 kbps is 172.8 MB. If the device runs out, the page says so, and you can convert one section at a time.
Turning the sound into text
An MP3 is sound and nothing else. GPT-Video goes one step further: it transcribes the speech in a video, times every word and renders animated captions into the clip. That runs on our servers and uses credits.
Related
Your file is processed on your device and never uploaded.