Apple’s lossless music format is called ALAC, with the suffix M4A.

ALAC is a lossless audio format developed by Apple. Apple has open sourced the "Apple Lossless Audio Codec" under the Apachev2.0 license.

On November 2, 2011, Apple announced a major news that the ALAC format will be officially open source. Apple announced that the lossless audio compression format ALAC is open source. Originally, the ALAC format only supports Apple devices such as iPhone, iPad, iPod, and Mac. However, another lossless audio compression format FLAC is more commonly used on computers, MP3, and MP4, but in After Apple announced that it will open source ALAC, the situation will become complicated. Apple seems to be opening up its closed garden.

Many speech compression methods use irreversible compression methods to obtain high compression ratios by reducing data during compression. Reversible compression (lossless compression) is the same as ordinary file compression, and can completely restore the compressed data to the previous data. In principle, it is a compression method that does not deteriorate the sound quality at all.