How to use it
- Add your file. Drop it on the box or choose it from your device.
- Set it up. Choose the quality. 128 kbps sounds good for music; 64 kbps mono is fine for speech.
- Compress MP3. Press Compress MP3. Long or large files take a while on phones.
- Download. Save the result.
What happens to your file
The MP3 is re-encoded with LAME at the bit rate you choose. Tags such as title and artist are kept.
How small can an MP3 get?
- An MP3’s size is fixed by its bit rate: 128 kbps is about 0.96 MB per minute, 64 kbps about 0.48 MB.
- Switching stereo to mono halves the data the encoder must describe, which helps a lot for speech.
- Each re-encode loses a little more detail, so compress once from the original rather than step by step.
- Upload forms that ask for a size in KB usually mean kilobytes of 1,024 bytes; the tool reports exact sizes so you can check.
- Audiobooks and lectures stay intelligible at 48 kbps mono; music starts to sound swishy below about 112 kbps.
Questions
Is my file uploaded?
No. Everything happens inside your browser with FFmpeg compiled to WebAssembly. Your file never leaves your device.
Is there a size limit?
Only your device’s memory. Files up to a few hundred MB work on most computers; phones manage smaller files.