Compress MP3

What this does

There is only one way to make an MP3 meaningfully smaller, and it is to throw more of the audio away. Compressing here means decoding the file and encoding it again at a lower bitrate: a 320 kbps track re-encoded at 128 comes out at roughly 40% of its size. That is a real reduction, not a trick of packing.

What you are actually trading

An MP3 is already compressed, so this is a second lossy pass over audio that has been through one. Each pass works from what the last one left, which is why the result sits a little further from the original recording than the file you started with. The practical rule follows: choose a bitrate below what your file already has, and no lower than you need. Speech is comfortable at 96 or 128 kbps. Music that people will actually sit and listen to should not go below 128, and 192 is where most stop hearing the loss. Choosing a bitrate at or above your source compresses nothing — it re-encodes the same audio into a larger file, and the readout above will tell you when that is about to happen.

Nothing is uploaded

The conversion happens inside this page. Your file is read by the browser, converted here, and saved straight back to your downloads. It is never sent to a server, so there is no upload wait and no size cap beyond what your own device can hold.

The first conversion is slower

The converter is about 32 MB and downloads the first time you use it, which is the one moment this page is not instant. After that it is cached, and later conversions start immediately, even offline. So do later visits.

Questions