AMR to MP3

What this does

AMR is a speech codec — the one older Android phones used for call recordings and voice memos, and the one that still comes out of some voicemail systems and desk phones. It is built for one purpose and does it at extraordinarily small sizes.

AMR is what older Android call and voice recorders produced. It is built for speech, and very little still opens it.

Why it sounds the way it does

AMR narrowband samples at 8 kHz and encodes between 4.75 and 12.2 kbps. That is telephone bandwidth, tuned by modelling a human voice rather than by storing a waveform — which is why speech stays intelligible at a bitrate where music would be noise, and why music in an AMR file already sounds broken before you touch it. Converting to MP3 makes it playable everywhere; it cannot make it wider than 8 kHz. A 64 kbps mono MP3 already carries everything the AMR contained, and a higher setting only stores the same limits in more detail.

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.

Open your browser’s developer tools, switch to the network panel, and convert a file. You will see the converter itself download once, and no upload of your audio at all. That is the whole difference between this and a site that converts on a server, and what that difference actually means is worth a read.

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