MP4 to MP3 Converter
Extract the audio track from any MP4 video and save it as an MP3, with a choice of bitrate. Free, no sign-up, and everything runs in your browser.
Powered by ffmpeg.wasm (WebAssembly). No upload, no account, no watermark.
How the MP4 to MP3 converter works
An MP4 file is a container that bundles a video stream with an audio stream, usually AAC. When you only need the sound, a music video, a recorded lecture, a voice memo exported as video, this tool decodes that audio track and re-encodes it as an MP3 with libmp3lame, the reference MP3 encoder. The video stream is discarded entirely, so the result is a fraction of the original size.
Everything runs in your browser using ffmpeg.wasm, a WebAssembly build of FFmpeg. The first time you convert, the page downloads the converter engine (about 32MB); your browser caches it, so later conversions start right away. Your video is never uploaded to any server: you can disconnect from the internet after the engine loads and the conversion still works.
MP3 is a lossy format, so re-encoding always trades a little quality for size. The default 192k bitrate is a good balance for most material. Pick 128k for speech-only recordings where size matters most, or 256k/320k for music where you want the highest quality MP3.
Tips for best results
| Situation | What to do |
|---|---|
| Music video or concert recording | Use 256k or 320k for the cleanest sound |
| Lecture, podcast or speech | 128k is plenty and produces the smallest file |
| Very long video (over an hour) | Encoding runs on your device's CPU, so allow a few minutes and keep the tab in the foreground |
| File much larger than 200MB | Conversion is possible but memory-hungry; trim the clip first if your device struggles |
Frequently asked questions
Is MP4 to MP3 conversion lossless?
No. MP3 is always a lossy format: the audio is decoded from the video and re-encoded, discarding some detail. At 256k or 320k the result is indistinguishable from the original for most listeners. If you need a bit-perfect copy of the audio track, this MP3 tool is not the right approach.
Why does the conversion take a while?
The converter runs on your own device's processor using WebAssembly, not on a server. Short clips finish in seconds; long videos encode at roughly real-time speed or faster on a modern laptop. Nothing is uploaded, so your internet speed does not matter after the one-time engine download.
Is there a file size limit?
There is no hard limit, but the file is held in browser memory, so files above about 2GB will not fit. Files under about 200MB convert most comfortably; very large files may be slow on low-memory devices.
Does my video get uploaded anywhere?
No. Conversion happens entirely in your browser with ffmpeg.wasm. After the one-time engine download you can even go offline and it will still work. Your file never leaves your device.
Which bitrate should I choose?
192k is the recommended default for a balance of size and quality. Choose 128k for speech-only audio, 256k for music you care about, and 320k for the highest quality MP3 possible.