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macOS is the current marketing name for Apple's Macintosh Operating System. This OS was previously known as OS X, and Mac OS X before that (which itself succeeded the 'classic' Mac OS).

macOS logo


macOS (10.12 and later), formerly known as OS X (from 10.7 to 10.11) and before that Mac OS X, is an operating system created and distributed by Apple Inc. for their Macintosh line of computers. More than 10 major versions have been released since the 1999 debut of Mac OS X Server 1.0.

Beginning with macOS 10.12 Sierra, Apple is transitioning away from the name "OS X". Sierra is exclusively referred to as macOS in both the software and documentation. They are also beginning to retroactively refer to older versions in this manner as well, i.e. macOS El Capitan or macOS Mavericks, both in documentation as well as in the Startup Disk selection screen in Sierra.

The change in branding was made to align the Macintosh operating system more closely with its offshoots, including , , , and .

Prior to this, as of OS X 10.7 Lion, the word "Mac" in Mac OS X was dropped from all marketing and promotional material. Upon the release of OS X 10.8 Mountain Lion, the "Mac" portion of the name was dropped completely, leaving it simply as "OS X" until Sierra was released on September 20, 2016.

Although many people pronounced OS X literally as "Oh ess ex", it was in fact pronounced "Oh ess ten", as the X being used is the Roman numeral for "ten".


This tag is for any and all questions related to the macOS operating system software. For hardware, use .

Related Tags

There are several -related tags which allow you to specify your operating system version, such as:

It is suggested that if you are asking questions about features of, applications included with, or possible bugs in a particular version of macOS, that you add the appropriate tag from the Related list above (such as or ), to allow users to easily distinguish when questions may or may not apply to their own circumstances.

For questions regarding Mac OS X Server prior to Lion, use .
For questions regarding for Lion and newer, use .