macOS X

Updated: 06/06/2021 by Computer Hope
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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.


Some may abbreviate macOS X as OSX.

Apple terms, Operating system, Operating system terms, X