Windows XP is a major release of the Windows NT operating system developed by Microsoft. It is the direct successor to both Windows 2000 for professional users and Windows Me for home users, and was released to manufacturing on August 24, 2001, and later to retail on October 25, 2001.
Development of Windows XP began in the late 1990s under the codename "Neptune", built on the Windows NT kernel that was intended specifically for mainstream consumer use. An updated version of Windows 2000 was also originally planned for the business market; however, in January 2000, both projects were scrapped in favor of a single OS codenamed "Whistler", which would serve as a single platform for both consumer and business markets. As such, Windows XP is the first consumer edition of Windows not to be based on the Windows 95 kernel and MS-DOS.
Upon its release, Windows XP received critical acclaim, with many noting increased performance and stability (especially in comparison to Windows Me), a more intuitive user interface, improved hardware support, and expanded multimedia capabilities. However, some industry reviewers were concerned by the new licensing model and product activation system. Windows XP and Windows Server 2003 were succeeded by Windows Vista and Windows Server 2008, released in 2007 and 2008, respectively.
Mainstream support for Windows XP ended on April 14, 2009, and extended support ended on April 8, 2014, after which the operating system ceased receiving further support or security updates. Windows Embedded POSReady 2009, based on Windows XP Professional, received security updates until April 2019. Unofficial methods were made available to apply the updates to other editions of Windows XP, but Microsoft discouraged this practice, citing incompatibility issues. As of August 2021, 0.6% of Windows PCs run Windows XP (on all continents the share is below 1%), and 0.18% of all devices across all platforms run Windows XP. Windows XP is still very prevalent in many countries, such as Armenia, where over 60% of computers use it.