APE (Monkey's Audio Lossless Audio) is a lossless compression audio format used for storage of audio data compressed with the Monkey's Audio algorithm originally developed in 2000 by Matthew T. Ashland.
Similar to other lossless audio compression formats, APE files retain the sound quality of the original recording and can be used as a source for its exact reconstruction.
At the same time, APE files are much smaller in size compared to the original source, due to the advanced compression techniques that the algorithm is based on. Tests even show that the Monkey's Audio algorithm achieves slightly better compression rates in comparison to other popular lossless compression formats like FLAC or WV.