Microsoft Windows is a computer operating system developed by Microsoft. It was first launched in 1985 as a graphical operating system built on MS-DOS. The initial version was followed by several subsequent releases, and by the early 1990s, the Windows line had split into two separate lines of releases: Windows 9x for consumers and Windows NT for businesses and enterprises. In the following years, several further variants of Windows would be released: Windows CE in 1996 for embedded systems; Pocket PC in 2000 (renamed to Windows Mobile in 2003 and Windows Phone in 2010) for personal digital assistants and, later, smartphones; Windows Holographic in 2016 for AR/VR headsets; and several other editions.
Windows MultiPoint Server was an operating system based on Windows Server. It was succeeded by the MultiPoint Services role in Windows Server 2016 and Windows Server version 1709. It was no longer being developed in Windows Server version 1803 and later versions.
The Surface RT (shown with keyboard cover attached) was the flagship Windows RT device upon its release.
In 2012 and 2013, Microsoft released versions of Windows specially designed to run on ARM-based tablets; these versions of Windows, named "Windows RT" and "Windows RT 8.1," were based on Windows 8 and Windows 8.1, respectively. Upon the release of Windows 10 in 2015, the ARM-specific version for large tablets was discontinued; large tablets (such as the Surface Pro 4) were only released with x86 processors and could run the full version of Windows 10. Windows 10 Mobile had the ability to be installed on smaller tablets (up to nine inches); however, very few such tablets were released, and Windows 10 Mobile primarily ended up only running on smartphones until its discontinuation. In 2017, the full version of Windows 10 gained the ability to run on ARM, thus rendering a specific version of Windows for ARM-based tablets unnecessary.
Originally announced at the 1991 Microsoft Professional Developers Conference, Cairo was the codename of a project whose charter was to build technologies for a next-generation operating system that would fulfill Bill Gates's vision of "information at your fingertips". Cairo never shipped, although portions of its technologies have since appeared in other products.
Neptune, based on the Windows 2000 codebase, was planned to be the first version of Microsoft Windows NT to have a consumer edition variant. A version was sent out to testers but was never released. The teams working on Neptune and Odyssey eventually combined to work on Windows XP.
Odyssey was planned to be the successor of Windows 2000. The teams working on Neptune and Odyssey eventually combined to work on Windows XP.
Triton was planned to be the successor of Windows Neptune and had been scheduled to be released in March 2001.
Blackcomb was originally planned to be a release of Windows following Windows XP. However, due to the large feature scope planned for Blackcomb, a smaller release codenamed "Longhorn" was planned first, and Blackcomb was delayed to 2003/2004. Both projects faced delays; Longhorn would go on to be released to consumers as "Windows Vista" in January 2007, while development on Blackcomb continued until the Blackcomb project was renamed "Vienna" in early 2006.
Vienna replaced Blackcomb and was intended as Windows Vista's successor. Vienna was eventually cancelled in favor of a new project codenamed "Windows 7" (which went on to be released in 2009 with the same name).
Microsoft had been reported as working on a new "lite" version of Windows as early as December 2018. Such a version was officially announced under the name "Windows 10X" at an event in October 2019; the operating system was intended to first launch on dual-screen devices. In May 2020, Microsoft announced that Windows 10X would instead be launching on single-screen PCs, such as laptops and 2-in-1 devices, first. However, on May 18, 2021, Microsoft announced that Windows 10X would not be launching (at least not in 2021); many of its features were instead rolled into Windows 11.
Originally a successor of Windows Mobile, it had been scrapped for Windows Phone 7
Cancelled when Microsoft "wound down" its phone efforts.
Much of the work that was put into Andromeda was migrated into Santorini. The Surface Duo, a dual-screen Android-powered smartphone launched by Microsoft in 2020, was loosely based on the prototype hardware that had been used to test Andromeda.
^Windows 10 Pro for Workstations became a Windows 10 edition starting with version 1709. Prior versions of Windows 10 do not include this as an edition.
^Windows 10 versions 1507 and 1511 do not include a "Windows 10 Pro Education" edition; that edition was only added with version 1607.
^Windows 10 S is only available in version 1703 and 1709.
^Windows 10 Enterprise LTSC is only available for versions 1507, 1607, 1809, and 21H2. It had originally been named Windows 10 Enterprise LTSB in version 1507.
^October 14, 2025 is the general end-of-support date for Windows 10. Specific versions and editions of Windows 10 have different end of support dates; see Windows 10 version history for a breakdown of dates by version and edition.
^Vibranium was the codename for Windows 10 version 2004. During the 20H2, 21H1, and 21H2 development cycles, builds were compiled under the codenames Manganese, Iron, and Cobalt, respectively. However, the versions of 20H2 and 21H1 that were released were built on top of version 2004 instead of these new builds. Windows 10 version 21H2 was similarly built on top of the Vibranium/2004 codebase instead of the Cobalt codebase; Cobalt builds were instead used as the base for the first version of Windows 11 (which had a core based on Cobalt in addition to a UI codenamed Sun Valley, and which also carries the version 21H2).
^The core of Windows 11 version 21H2 is codenamed Cobalt; the "Sun Valley" codename refers to the UI layer of Windows 11 version 21H2 and is commonly used to address Windows 11 version 21H2 as a whole.
^ abcThe end-of-support date listed in the table refers to Home and Pro editions. The date for other editions, such as Education and Enterprise, may differ.
^July 2007 is when it was reported that the Vista's successor was codenamed "7", rather than "Vienna", indicating that Vienna's discontinuation had occurred by then. However, Vienna may have been cancelled prior to then.
^While Santorini was the general codename for Windows 10X, Centaurus was the specific codename for Windows 10X on foldable PCs and Pegasus was the codename for Windows 10X on "traditional" PCs (such as laptops or 2-in-1 computers).
^ abDate refers to when the cancellation of the operating system was announced. The decision for the operating system to be cancelled may have occurred prior to then.
^Martens, China (July 22, 2005). "Update:Microsoft's Longhorn becomes Windows Vista". IDG Communications, Inc. Retrieved 13 June 2021. Microsoft Corp. has announced the official name for its upcoming operating system, previously known under the code name Longhorn. The operating system, now due out in 2006, will be called Windows Vista
^Warren, Tom (24 November 2014). "Windows 10 won't be Windows 6.4". The Verge. Vox Media, LLC. Retrieved 3 January 2022. Windows 10 Technical Preview builds are currently identified as Windows NT 6.4, but future builds will include the change
^Bowden, Zac (September 18, 2020). "Project Andromeda:The secret history of Windows on Surface Duo". Windows Central. Future US, Inc. Retrieved 16 July 2021. Microsoft had originally planned to ship CShell on Windows 10 Mobile under the codename Pheonix [sic], but that plan very quickly went away once the company decided to wind down its existing phone efforts in early 2017.