Monkey’s Audio is a file format for audio data compression. Being a lossless compression format, Monkey’s Audio does not remove information from the audio stream, as lossy compression formats such as MP3, AAC, and Vorbis do.
Like other methods of compression, the main advantage of using Monkey’s Audio lies in a reduction of bandwidth and/or a reduction in storage requirements. A digital recording (such as a CD) encoded to Monkey’s Audio format can later be decompressed into an identical copy of the original audio data. Like the Apple Lossless format, files encoded to Monkey’s Audio are typically reduced to about half of the original size.
Monkey’s Audio is a proprietary software, it is often too slow to decode on portable audio devices, and it has limited/problematic support on software platforms other than Windows. There are alternatives that provide the user with more freedom and support for more platforms, such as the FLAC and WavPack formats.
Monkey’s Audio files use the filename extension .ape for audio and .apl for track metadata info.
Monkey’s Audio is not free software (but is freeware) or open source, but has a peculiarly ambiguous license. Most Linux distributions and other operating systems that rely on only free software could not include it and the software ecosystem around Monkey’s Audio is less varied than that of other, more freely licensed lossless compressors such as FLAC. Since FLAC is pre-installed with most Linux distributions, FLAC is typically preferred by users running that operating system. The older Shorten format has been used for many years in the live taping community. Sites such as etree typically still use Shorten, though some are beginning to move to FLAC.
Since Monkey’s Audio is a lossless compression method, it is not readily comparable with lossy compression methods such as MP3, Ogg Vorbis and AAC. The two different types of formats have different aims. The aim of lossless compression is to preserve an exact reproduction of the original file in as small a space as possible. The aim of lossy codecs is to discard sound data to fit the user's amount of file space (or bit rate) specified by the user while retaining as much quality as possible. Lossless audio formats therefore tend to be significantly larger than lossy formats. A typical Monkey’s Audio file will be approximately 3-5 times larger than a lower-quality 192kb/sec bitrate MP3 lossy audio file.
However, while the license text claims to permit using the official Monkey's Audio codec in GPL projects, several Linux distribution maintainers have found the license to be contradictory. It does not permit redistribution nor modification, and thus cannot be considered open source or free software.
On hardware platforms, the open source jukebox firmware project Rockbox supports playback of Monkey's Audio on most of its supported targets, but most targets lack sufficient CPU power to play back the codec in real time on all but the lowest compression settings.