ALAC (Apple Lossless)
Apple's lossless audio codec from 2004 — what FLAC does, in Apple's own packaging.
ALAC shipped with iTunes 4.5 and QuickTime in 2004. Like FLAC it relies on linear prediction: each sample is guessed from the ones before it and only the error is stored, which typically yields files 40–60 % of the original size. Decoding returns exactly the same bits, so it is genuine lossless compression. The files live in an MP4 container with the .m4a extension, same as AAC — so the filename alone won't tell you whether you've got lossless or not.
It existed because Apple wanted something the iPod could play and that Apple controlled. The source was released under Apache 2.0 in 2011, and in 2021 ALAC became the format behind Apple Music's lossless streaming.