Read the container
The MP4 index is read locally. Every audio track is listed with its codec, channel count and sample rate, so a second language track is not silently ignored.
Browser tool · nothing uploaded
MP4 to MP3, converted in your browser.
Drop an MP4 and get the audio track back as MP3. The video is dropped, the audio is decoded and re-encoded on this device, and the file is never uploaded.
.mp4 → .mp3No uploadBatch and trim64–320 kbps
converter local
ready nothing uploaded
Output settings
Optional. Use mm:ss or h:mm:ss. Batch conversion uses the full file.
Converting… 0%
The MP3 was written in this tab. No upload request was made.
01
What this converter does
mp4tomp3.net converts MP4 video to MP3 audio in the browser; the file is never uploaded.
The MP4 container is read from your disk, the video track is dropped without being decoded, and the audio track is decoded and re-encoded as MP3. The output is written in this tab and offered as a download. There is no upload endpoint, no account and no queue.
If you need the reverse direction, or a different source format, this page is deliberately single-purpose. The how-it-works page explains the engine, the browser requirements and the cases where the converter will refuse a file rather than write a broken one.
02
How it works
Drop the picture, decode the sound
The video track is discarded without being decoded. Only the audio samples are decoded, then resampled or downmixed if the MP3 encoder needs it.
Write the MP3
A WASM build of LAME encodes the selected bitrate in a worker. The finished MP3 is handed to the browser as a local file; no request carries your audio.
03
What changes in the file
| Property | Result | Notes |
|---|---|---|
| Video track | Dropped | The picture is never decoded or re-encoded. |
| Audio codec | Usually AAC → MP3 | AAC is decoded, then LAME writes MP3. |
| Bitrate | 64–320 kbps CBR | CBR is predictable; VBR is not offered. |
| Channels | Mono or stereo | Sources wider than stereo are downmixed to stereo. |
| Sample rate | MP3 rates only | 96 kHz sources are resampled to 48 kHz; 88.2 kHz to 44.1 kHz. |
| Metadata | Basic tags may carry over | Chapters and cover art are not guaranteed. |
| Trim | Optional | Start and end are applied before encoding. |
Before you convert
Only convert files you have the right to use. The tool does not fetch URLs, bypass DRM or download from streaming services.
04
Guides for this format
Guide
MP4 to MP3 at 320 kbps
320 kbps is the maximum MP3 bitrate. What it does to an MP4's AAC track, when it is wasted, and how to set it without guessing.
GuideMP4 to MP3 on a Mac
QuickTime exports M4A, not MP3. Here are the three Mac routes that actually produce MP3: browser, Terminal ffmpeg, and the limits of each.
GuideMP4 to MP3 on an iPhone
The iPhone route that works: save the video to Files, open the converter in Safari 26+, convert, and save the MP3 back to Files. No app, no upload.
Guideffmpeg MP4 to MP3
The exact ffmpeg flags for extracting MP3 from MP4, a batch loop, and an honest comparison with the browser converter.
05
Questions
Are my files uploaded anywhere?
No. The MP4 is read from disk by the browser and processed in this tab. There is no upload endpoint, so there is no server-side copy to delete or leak.
Is the converter free?
Yes. There is no account, no payment, no per-file limit and no watermark. The practical limit is the memory of your device, not an upload quota.
Will converting MP4 to MP3 lose quality?
Yes, a little. The audio inside an MP4 is usually AAC, and MP3 is a different lossy codec, so the sound is decoded and encoded again. Choose a bitrate at or above the source bitrate to keep the second generation as small as possible. MP3 cannot be lossless.
Can I convert several MP4 files at once?
Yes. Drop multiple files and they are processed one after another, so memory use stays bounded. Each finished MP3 can be downloaded on its own or as a ZIP when the total is under 500 MB.
Does it work on iPhone and Mac?
Yes, in Safari 26 or newer on macOS and iOS. Chrome/Edge 94+ and Firefox 130+ also work. Older Safari versions do not expose the WebCodecs audio decoder this tool needs, and the page says so instead of failing silently.
What if the MP4 has no audio?
The file is rejected with a clear message. Silent screen recordings and some exports have no audio track; there is nothing to extract, and the tool will not write an empty MP3.
06
Limits, stated up front
- No upload limit, but a memory limit. The file is read lazily from disk; the output still has to fit in the tab. Very large files can exhaust a phone or a low-memory laptop.
- MP3 is lossy. The converter never claims otherwise. It re-encodes the audio; choose a bitrate at or above the source to avoid stacking more loss than necessary.
- Not every codec is supported. The browser must be able to decode the audio track. ALAC, AC-3, DTS, WMA, AMR and DRM-protected files are rejected with a clear message.
- No URL input. The file must be on your device. The tool does not fetch from streaming services or bypass DRM.
The full support matrix and browser requirements are on how it works. Privacy details are on privacy.