AMR file contains audio data in one fo the following format: AMR-NB (lower quality, narrowband) or AMR-WB (higher quality, wideband). Audio data is compressed using dedicated speech encoding algorithm (ACELP).

Many mobile devices, such as voice recorders/dictaphones, cellular phones, or tablets, use AMR format to record audio data, for sound notifications, and ringtones. MMS messages also use this audio format. AMR format was developed by Ericsson.