macOS X
Updated: 06/06/2021 by Computer Hope
macOS, originally named macOS X, is an operating system released by Apple on March 16, 1999, for servers. It was later released for desktop computers on March 24, 2001, and is a completely new Apple Macintosh operating system based on BSD (Berkeley Software Distribution).
Apple code-named each release of the macOS using names of big cats or places in California, except macOS Server 1.0. See our Apple OS history for a listing of the macOS releases, including codenames.
Tip
Some may abbreviate macOS X as OSX.