Convert MP4 to MP3
Keep the sound, drop the picture. Your MP4 is converted on this device, as fast as it can read the file.
- Nothing is uploaded
- Works offline
- Open source
- No limits, no watermark
Done
Open the network tab. It stays empty.
Add files and run the tool to see every request this tab makes.
Your files are processed on this device and never sent to a server. Reload the page to clear everything from memory.
An MP4 is a container holding a video track and, usually, an AAC audio track. Converting MP4 to MP3 means reading that audio track, decoding it, and encoding it again as MP3, the one audio format that plays in every car stereo, old phone, DJ app and podcast host. The picture is simply left behind, which is why the MP3 is a small fraction of the size of the video.
Most MP4 to MP3 sites upload the entire video to their server first. On a phone connection a 500 MB recording can take longer to upload than to convert, free plans stop at 100 or 200 MB, and the file sits on someone else’s disk while it waits in a queue. Here your browser does the decoding itself and the MP3 encoder (LAME, the same encoder behind most MP3 software for two decades) runs inside the page, so a large file only costs the time your device needs to read it.
The default of 192 kbps stereo keeps music indistinguishable from the original for nearly everyone. Lectures, sermons, interviews and meeting recordings sound the same at 96 or 128 kbps in mono and come out several times smaller. Drop several MP4s at once and they are converted one after another; download them one by one or as a single zip.
How it works
- Drop one or more MP4 files, or tap to pick them from your files or camera roll.
- Keep MP3 at 192 kbps for music, or choose 96 to 128 kbps and mono for speech.
- Convert. The MP3 downloads when it is ready; several files come as a zip.
In your browser, not on a server
Your browser decodes the sound track with the same audio decoders it uses to play media on any website (AAC for MP4, MOV and M4A; Opus or Vorbis for WebM; FLAC, WAV and MP3). The samples are resampled to 44.1 kHz and handed to LAME, the reference MP3 encoder, compiled to WebAssembly and served by this site. WAV files are written directly by a few lines of code in the page. Everything happens in memory in your tab.
Compared with upload-based tools: Online converters upload the whole video just to keep its sound, cap free files at a few hundred megabytes, and make you wait in a queue. Home videos, lectures and voice memos are personal. Here the file never leaves your device, so a 2 GB video converts as fast as your computer can read it.
Verify it yourself. Load this page, turn off Wi-Fi or switch to airplane mode, and run the tool. Or open your browser's developer tools (F12, or Cmd-Option-I on a Mac), pick the Network tab, and watch it while you convert. The panel above does the same count for you.
Questions
Does converting MP4 to MP3 lose quality?
The sound in an MP4 is already compressed (usually AAC at 128 to 256 kbps), and MP3 compresses it again. At 192 kbps or higher the difference is not audible in normal listening; at 320 kbps it is as close as MP3 gets. The only lossless way to keep the track is to choose WAV, which is much larger.
How long does it take?
Usually a few seconds per minute of audio on a laptop and somewhat longer on a phone. There is no upload or queue, so the time depends only on your device.
My MP4 has no sound in the MP3. Why?
Some MP4s, such as screen recordings made without a microphone or clips exported from a GIF, have no audio track at all. The tool tells you when it cannot find one.
Is the file uploaded anywhere?
No. There is no server in this process. The page is a static file and the work is done by code running inside your browser tab. You can load the page, turn off Wi-Fi, and it still works.