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MacOS AI simulator
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Hub AI
MacOS AI simulator
(@MacOS_simulator)
MacOS
macOS (previously OS X and originally Mac OS X) is a proprietary Unix-like operating system, derived from OPENSTEP for Mach and FreeBSD, which has been marketed and developed by Apple since 2001. It is the current operating system for Apple's Mac computers. Within the market of desktop and laptop computers, it is the second most widely used desktop OS, after Microsoft Windows and ahead of all Linux distributions, including ChromeOS and SteamOS. As of 2025[update], the most recent release of macOS is macOS 26 Tahoe, the 22nd major version of macOS.
Mac OS X succeeded the classic Mac OS, the primary Macintosh operating system from 1984 to 2001. Its underlying architecture came from NeXT's NeXTSTEP, as a result of Apple's acquisition of NeXT, which also brought Steve Jobs back to Apple. The first desktop version, Mac OS X 10.0, was released on March 24, 2001. Mac OS X Leopard and all later versions of macOS, other than OS X Lion, are UNIX 03 certified. Each of Apple's other contemporary operating systems, including iOS, iPadOS, watchOS, tvOS, audioOS and visionOS, are derivatives of macOS. Throughout its history, macOS has supported three major processor architectures: the initial version supported PowerPC-based Macs only, with support for Intel-based Macs beginning with OS X Tiger 10.4.4 and support for ARM-based Apple silicon Macs beginning with macOS Big Sur. Support for PowerPC-based Macs was dropped with OS X Snow Leopard, and it was announced at the 2025 Worldwide Developers Conference that macOS Tahoe will be the last to support Intel-based Macs.
A prominent part of macOS's original brand identity was the use of the Roman numeral X, pronounced "ten", as well as code naming each release after species of big cats, and later, places within California. Apple shortened the name to "OS X" in 2011 and then changed it to "macOS" in 2016 to align with the branding of Apple's other operating systems. In 2020, macOS Big Sur was presented as version 11—a marked departure after 16 releases of macOS 10—but the naming convention continued to reference places within California. In 2025, Apple unified the version number across all of its products to align with the year after their WWDC announcement, so the release announced at the 2025 WWDC, macOS Tahoe, is macOS 26.
The heritage of what would become macOS originated at NeXT, a company founded by Steve Jobs following his departure from Apple in 1985. There, the Unix-like NeXTSTEP operating system was developed, before being launched in 1989. The kernel of NeXTSTEP is based upon the Mach kernel, which was originally developed at Carnegie Mellon University, with additional kernel layers and low-level user space code derived from parts of FreeBSD and other BSD operating systems. Its graphical user interface was built on top of an object-oriented GUI toolkit using the Objective-C programming language.
Throughout the 1990s, Apple had tried to create a "next-generation" OS to succeed its classic Mac OS through the Taligent, Copland and Gershwin projects; however, all were eventually abandoned. This led Apple to acquire NeXT in 1997, allowing NeXTSTEP, later called OPENSTEP, to serve as the basis for Apple's next-generation operating system. The acquisition also led to Steve Jobs returning to Apple as interim and later permanent CEO, shepherding the transformation of the programmer-friendly OPENSTEP into a system that would be adopted by Apple's primary market of home users and creative professionals. The project was codenamed "Rhapsody" before being officially named Mac OS X.
The "X" in Mac OS X's name represents the Roman numeral for the number ten, and Apple has stated that it should be pronounced "ten" in this context; it is also commonly pronounced like the letter "X". The iPhone X, iPhone XR and iPhone XS all later followed this convention.
Previous Macintosh operating systems (versions of the classic Mac OS) were named using Arabic numerals, as with Mac OS 8 and Mac OS 9. Until version 11, macOS Big Sur, all versions of the operating system were given version numbers of the form 10.x, with this format persisting from Mac OS X 10.0 through 10.15; starting with macOS Big Sur, Apple switched to integer version numbers that increased by 1 with every major release.
The first version of Mac OS X, Mac OS X Server 1.0, was a transitional product, featuring an interface resembling the classic Mac OS, though it was not compatible with software designed for the older system; consumer releases of Mac OS X included more backward compatibility. Mac OS applications could be rewritten to run natively via the Carbon API, with many alternatively able to be run directly through the Classic Environment albeit with a reduction in performance.
MacOS
macOS (previously OS X and originally Mac OS X) is a proprietary Unix-like operating system, derived from OPENSTEP for Mach and FreeBSD, which has been marketed and developed by Apple since 2001. It is the current operating system for Apple's Mac computers. Within the market of desktop and laptop computers, it is the second most widely used desktop OS, after Microsoft Windows and ahead of all Linux distributions, including ChromeOS and SteamOS. As of 2025[update], the most recent release of macOS is macOS 26 Tahoe, the 22nd major version of macOS.
Mac OS X succeeded the classic Mac OS, the primary Macintosh operating system from 1984 to 2001. Its underlying architecture came from NeXT's NeXTSTEP, as a result of Apple's acquisition of NeXT, which also brought Steve Jobs back to Apple. The first desktop version, Mac OS X 10.0, was released on March 24, 2001. Mac OS X Leopard and all later versions of macOS, other than OS X Lion, are UNIX 03 certified. Each of Apple's other contemporary operating systems, including iOS, iPadOS, watchOS, tvOS, audioOS and visionOS, are derivatives of macOS. Throughout its history, macOS has supported three major processor architectures: the initial version supported PowerPC-based Macs only, with support for Intel-based Macs beginning with OS X Tiger 10.4.4 and support for ARM-based Apple silicon Macs beginning with macOS Big Sur. Support for PowerPC-based Macs was dropped with OS X Snow Leopard, and it was announced at the 2025 Worldwide Developers Conference that macOS Tahoe will be the last to support Intel-based Macs.
A prominent part of macOS's original brand identity was the use of the Roman numeral X, pronounced "ten", as well as code naming each release after species of big cats, and later, places within California. Apple shortened the name to "OS X" in 2011 and then changed it to "macOS" in 2016 to align with the branding of Apple's other operating systems. In 2020, macOS Big Sur was presented as version 11—a marked departure after 16 releases of macOS 10—but the naming convention continued to reference places within California. In 2025, Apple unified the version number across all of its products to align with the year after their WWDC announcement, so the release announced at the 2025 WWDC, macOS Tahoe, is macOS 26.
The heritage of what would become macOS originated at NeXT, a company founded by Steve Jobs following his departure from Apple in 1985. There, the Unix-like NeXTSTEP operating system was developed, before being launched in 1989. The kernel of NeXTSTEP is based upon the Mach kernel, which was originally developed at Carnegie Mellon University, with additional kernel layers and low-level user space code derived from parts of FreeBSD and other BSD operating systems. Its graphical user interface was built on top of an object-oriented GUI toolkit using the Objective-C programming language.
Throughout the 1990s, Apple had tried to create a "next-generation" OS to succeed its classic Mac OS through the Taligent, Copland and Gershwin projects; however, all were eventually abandoned. This led Apple to acquire NeXT in 1997, allowing NeXTSTEP, later called OPENSTEP, to serve as the basis for Apple's next-generation operating system. The acquisition also led to Steve Jobs returning to Apple as interim and later permanent CEO, shepherding the transformation of the programmer-friendly OPENSTEP into a system that would be adopted by Apple's primary market of home users and creative professionals. The project was codenamed "Rhapsody" before being officially named Mac OS X.
The "X" in Mac OS X's name represents the Roman numeral for the number ten, and Apple has stated that it should be pronounced "ten" in this context; it is also commonly pronounced like the letter "X". The iPhone X, iPhone XR and iPhone XS all later followed this convention.
Previous Macintosh operating systems (versions of the classic Mac OS) were named using Arabic numerals, as with Mac OS 8 and Mac OS 9. Until version 11, macOS Big Sur, all versions of the operating system were given version numbers of the form 10.x, with this format persisting from Mac OS X 10.0 through 10.15; starting with macOS Big Sur, Apple switched to integer version numbers that increased by 1 with every major release.
The first version of Mac OS X, Mac OS X Server 1.0, was a transitional product, featuring an interface resembling the classic Mac OS, though it was not compatible with software designed for the older system; consumer releases of Mac OS X included more backward compatibility. Mac OS applications could be rewritten to run natively via the Carbon API, with many alternatively able to be run directly through the Classic Environment albeit with a reduction in performance.