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, iOS, watchOS, and tvOS. The derivatives of macOS are Apple's other operating systems: iOS, iPadOS, watchOS, tvOS, and audioOS.Ī prominent part of macOS's original brand identity was the use of Roman numeral X, pronounced 'ten', as well as code naming each release after species of big cats, or places within California. Mac OS X 10.5 Leopard, Mac OS X 10.6 Snow Leopard and all releases from OS X 10.8 Mountain Lion to macOS 14 Sonoma are UNIX 03 certified. The first desktop version, Mac OS X 10.0, was released on March 24, 2001. During this time, Apple co-founder Steve Jobs had left Apple and started another company, NeXT, developing the NeXTSTEP platform that would later be acquired by Apple to form the basis of macOS. MacOS succeeded the classic Mac OS, a Macintosh operating system from 1984 to 2001. Within the market of desktop and laptop computers, it is the second most widely used desktop OS, after Microsoft Windows and ahead of Linux (including ChromeOS). It is the primary operating system for Apple's Mac computers. MacOS ( / ˌ m æ k oʊ ˈ ɛ s/ previously OS X and originally Mac OS X) is an operating system developed and marketed by Apple Inc.