DeveloperApple, Inc.
Source modelClosed source (with open source components)
Initial releaseSystem Software 1
(24 January 1984)
Latest releasemacOS Sonoma (build 23F79)
(13 May 2024)
Latest previewmacOS Sequoia (build 24A5279h)
(24 June 2024)
Supported platformsx86_64, ARM64 (previously 68k, PPC and i386)
Kernel typeHybrid (XNU)
User interfaceAqua
LicenseProprietary (with open-source components)

macOS is a series of operating systems developed by Apple for their Macintosh platform. It was first introduced together with the original Macintosh in 1984. The system from the very beginning made use of a graphical interface, similar to the one used by the earlier Lisa. In its early versions, it only supported running a single application at a time, although it was later extended with cooperative multitasking support via MultiFinder. During Apple's transition from Motorola 68k series to the PowerPC architecture, Mac OS was also ported to the new platform by using emulation, until a new, native OS was developed as a part of the Copland project.

After the failure of Copland, however, Apple was forced to further maintain the original Mac OS codebase, which no longer satisfied the ever-increasing performance and stability requirements. Apple eventually saw the solution in buying out NeXT in 1997, the company founded by Steve Jobs after he was ousted from Apple. As a part of the deal, Apple gained NeXT's object-oriented operating system called NeXTSTEP based on Unix. The Unix core of NeXTSTEP was renamed to Darwin, released as open source and in the following years, it was modernized partially by using code from FreeBSD and other projects.

The classic Mac OS was eventually succeeded by Mac OS X in 2001 with the release of Mac OS X Cheetah. Since then, the system went through several architecture transitions, first from PowerPC to Intel x86 in 2006. In 2020, Apple began another transition, this time from x86 to the ARM-based Apple silicon.

History[edit | edit source]

Classic[edit | edit source]

The original Macintosh System Software is based on the Lisa OS and UI concepts from Xerox PARC. It uses a monolithic architecture but lacks support for memory management, protected memory, access controls, and conflict-free extensions. Only one application at a time could be supported under System Software until version 5 when MultiFinder was introduced. In 1997, Apple rebranded the Macintosh System Software to Mac OS. Mac OS would continue to be developed until the introduction of Mac OS X, after which Apple only delivered minor updates to the classic Mac OS. The final minor updates were designed to ease the transition to OS X. Carbon, an API introduced with Mac OS 8, works as the transitional API for classic Mac OS and Mac OS X applications.

The classic Mac OS was originally written for the Motorola 68k architecture. The 68k architecture was used from 1984 to 1994, after which Apple transitioned to PowerPC. PowerPC would be used until the classic Mac OS's discontinuation in 2002. Classic Mac OS was based on a simple kernel design, which eventually became too limited and crash-prone for applications. In response, Apple bought NeXT and used NeXTSTEP as a base to develop Mac OS X.

The Classic Mac OS can run standalone, and under Mac OS X using the Classic system layer. Only certain versions of Mac OS 9 can run under the Classic system layer, and the layer itself was dropped after Mac OS X Tiger.

UNIX-based[edit | edit source]

macOS (formerly called Mac OS X until 2012 and then OS X until 2016) is the current incarnation of Mac OS. The first version released was Mac OS X Server in 1999. Unlike the classic Mac OS, it is based on NeXTSTEP and uses its frameworks and architectures. In 2006, Apple switched to Intel-based x86 processors in Macs. Support for PowerPC in Mac OS X was dropped in 2009. In 2012, Apple began to use the OS X moniker to brand Mac OS X alongside their other operating systems (watchOS, tvOS, iOS). In 2016, Apple began to use the macOS moniker to brand OS X alongside their other operating systems (watchOS, tvOS, iOS, visionOS). In 2020, Apple declared that they would switch over to the Apple Silicon SoC in future Mac computers.

Timeline[edit | edit source]

Classic Mac OS versions

Name Versions Code name Release date Support end date Notes
System Software 1 1.0 - 1.1h 1984-01-24 1985-04-01
System Software 2 2.0 - 2.1 1985-04 1986-01-01
System Software 3 3.0 - 3.3 1986-01 1987-01-01
System Software 4 4.0 - 4.1.1 1987-01 1987-11-01
System Software 5 5.0 - 5.1 1987-10 1988-04-01
System Software 6 6.0 - 1988-04 1992-03
Mac OS 7 7.0 - 7.6.1 Big Bang 1991-05-13 2001-05 Version 7.1.2 introduced support for PowerPC Macs
Copland 8.0 Copland
Mac OS 8 8.0 - 8.6 Tempo 1997-07-26 2001-05 Version 8.5 dropped support for Motorola 68k Macs
Mac OS 9 9.0 - 9.2.2 Sonata 1999-10-23 2002-02-01 Version 9.2 dropped support for Macs with PowerPC 60x processors.
Never released
Old version
Older version, still supported
Current stable version
Latest preview version
Future release

UNIX-based macOS versions

Name Version Code name Release date Support end date Notes
OS Darwin
Mac OS X Server 1.x 1.x [a] Rhapsody 1999-03-16 2001-03-24 Identifies as Rhapsody 5.3 - 5.6
Mac OS X Public Beta 10.0 1.2.1 Kodiak 2000-09-13 2001-03-24[b] Introduced the Aqua interface
Mac OS X Cheetah 1.3.1 Cheetah 2001-03-24 2004
Mac OS X Puma 10.1 1.4.1 / 5 Puma 2001-09-25 2005
Mac OS X Jaguar 10.2 6 Jaguar 2002-08-23 2006
Mac OS X Panther 10.3 7 Pinot 2003-10-24 2007-03-04
Mac OS X Tiger 10.4 8 Merlot, Chardonay 2005-04-29 2009-09-04 Version 10.4.4 introduced support for Intel Macs
Mac OS X Leopard 10.5 9 Chablis 2007-10-26 2011-06-23 Introduced support for 64-bit Intel Macs
Mac OS X Snow Leopard 10.6 10 Snow Leopard 2009-08-28 2014-02-25 Introduced 64-bit kernel; dropped support for PPC Macs
Mac OS X Lion 10.7 11 Barolo 2011-07-20 2014-10-16 Dropped support for 32-bit Intel Macs; removed Rosetta
OS X Mountain Lion 10.8 12 Zinfandel 2012-07-25 2015-09-30 Removed the 32-bit kernel and 32-bit EFI bootloader
OS X Mavericks 10.9 13 Cabernet 2013-10-22 2016-09-20
OS X Yosemite 10.10 14 Syrah 2014-10-16 2017-09-25
OS X El Capitan 10.11 15 Gala 2015-09-30 2018-09-24
macOS Sierra 10.12 16 Fuji 2016-09-20 2019-10-07
macOS High Sierra 10.13 17 Lobo 2017-09-25 2020-11-12
macOS Mojave 10.14 18 Liberty 2018-09-24 2021-10-25
macOS Catalina 10.15 19 Jazz 2019-10-07 2022-10-24 Dropped support for 32-bit applications
macOS Big Sur 11 20 Golden Gate 2020-11-12 2023-09-26 Introduced support for Apple silicon Macs
macOS Monterey 12 21 Star 2021-10-25 TBA
macOS Ventura 13 22 Rome 2022-10-24 TBA
macOS Sonoma 14 23 Sunburst 2023-09-26 TBA
macOS Sequoia 15 24 Glow Fall 2024 TBA Future release
Never released
Old version
Older version, still supported
Current stable version
Latest preview version
Future release

Notes[edit | edit source]

  1. Mac OS X Server 1.x is a direct descendant of the NeXTSTEP/OPENSTEP codebase and is not based on Darwin.
  2. Expired on 14 May 2001