MP4 to MP3 Converter
Your files never leave your device
Conversion runs inside your browser using WebAssembly. Nothing is uploaded; the only downloads are this page and the conversion engine. You can confirm it in your browser's network tab.
Why convert MP4 to MP3?
To keep just the sound from a video: a lecture, interview, music performance or voice note recorded as video.
What changes in the MP3
- The video track is discarded; the MP3 is usually a small fraction of the MP4’s size.
- The AAC audio in the MP4 is decoded and re-encoded as MP3, a lossy-to-lossy step that is inaudible at the quality used.
- Chapter markers and subtitles are not kept.
How Convertz converts it
FFmpeg (WebAssembly) encodes MP3 with LAME at VBR quality 2, typically 170–210 kbps, which most listeners can’t tell from the source. Title, artist and album tags are copied as ID3v2.3.
Everything happens on your device; the file is never uploaded.
Common pitfalls
- Only extract audio from videos you have the right to use.
- If the video has several audio tracks (for example, different languages), only one is extracted: FFmpeg picks the one with the most channels.
MP4 vs MP3
| Property | MP4 | MP3 |
|---|---|---|
| Full name | MPEG-4 Part 14 | MPEG-1 Audio Layer III |
| Compression | Depends on codec (usually H.264) | Lossy |
| Transparency | No (in practice) | — |
| Works with | Essentially everything, when the video is H.264 with AAC audio. | Every audio player, phone, car stereo and editing app. |
What is MP4?
The most widely supported video container. MP4 files usually hold H.264 or HEVC video with AAC audio, and play on virtually every phone, browser, TV and editing app.
What is MP3?
The universal compressed audio format, standardised in 1993. It removes sounds that are masked by louder ones; at 190 kbps or more most listeners can’t tell it from the original. Its patents expired in 2017.
Related conversions
The converter also handles 22 input formats in total. See all formats