List of Microsoft codenames

Microsoft codenames are given by Microsoft to products it has in development before these products are given the names by which they appear on store shelves. Many of these products (new versions of Windows in particular) are of major significance to the IT community, and so the terms are often widely used in discussions before the official release. Microsoft usually does not announce a final name until shortly before the product is publicly available. It is not uncommon for Microsoft to reuse codenames a few years after a previous usage has been abandoned.

There has been some suggestion that Microsoft may move towards defining the real name of their upcoming products earlier in the product development lifecycle to avoid needing product codenames.

Operating systems

Windows 3.x and 9x

Codename	Preliminary name	Final name	Notes	Ref
Janus	—N/a	Windows & MS-DOS 5	Combined bundle of Windows 3.1 and MS-DOS 5. Janus is a Roman god usually depicted with two faces, here symbolizing the previously separate Windows and MS-DOS products.
Jastro	—N/a	Windows & MS-DOS 6	Combined bundle of Windows 3.1 and MS-DOS 6. Portmanteau of Janus and Astro, the codename of MS-DOS 6.
Sparta, Winball	Windows 3.1 Plus	Windows for Workgroups 3.1	Windows 3.1 (16-bit) with enhanced networking; designed to work particularly well as a client with the new Windows NT.
Snowball	—N/a	Windows for Workgroups 3.11	An updated version of Windows for Workgroups 3.1, which introduces 32-bit file access and network improvements. It also removes the Standard Mode, effectively dropping support for 16-bit x86 processors.
Chicago	Windows 4.0, Windows 93, Windows 94	Windows 95	For codenames of some of the internal components of Windows 95, see "Jaguar", "Cougar", "Panther" and "Stimpy" under § OS components
Detroit	—N/a	USB Supplement to Windows 95 OSR2	Named after Detroit, Michigan. A writer for Maximum PC suggested that "Detroit" and other Windows 95-era names were answers to the question posed by Microsoft's "Where do you want to go today?" marketing campaign.
Nashville	Windows 96	Dropped	Named after Nashville. Cancelled upgrade for Windows 95; sometimes referred to in the press as Windows 96. Codename was reused for Internet Explorer 4.0 and Windows Desktop Update which incorporated many of the technologies planned for Nashville.
Memphis	Windows 97	Windows 98	—N/a
Millennium	—N/a	Windows Me	ME stands for Millennium Edition; Microsoft states that it is pronounced Me.

Windows NT family

Codename	Preliminary name	Final name	Notes	Ref
Razzle	NT OS/2, Advanced Windows	Windows NT 3.1	Is also the name of a script that sets up the Windows NT development environment. NT OS/2 reflected the first purpose of Windows NT to serve as the next version of OS/2, before Microsoft and IBM split up. Microsoft used the NT OS/2 code to release Windows NT 3.1.
Daytona	—N/a	Windows NT 3.5	Named after the Daytona International Speedway in Daytona Beach, Florida.
Cairo	—N/a	Dropped	A cancelled project that would have fulfilled Bill Gates' "Information at your fingertips" vision
Shell Update Release	—N/a	Windows NT 4.0	—N/a
Wolfpack	—N/a	Microsoft Cluster Server	—N/a
Janus	—N/a	Dropped	Codename for the proposed 64-bit edition of Windows 2000, which was never released.
Impala	—N/a	Windows NT 4.0 Embedded	—N/a
Neptune	—N/a	Dropped	Planned to be the first consumer-oriented release of Windows NT succeeding the Windows 9x series; merged with Odyssey to form Whistler.
Triton	—N/a	Dropped	A cancelled successor to "Neptune".
Asteroid	—N/a	Windows 2000 Service Pack 1	—N/a
Odyssey	—N/a	Dropped	Planned to be a successor to Windows 2000; merged with Neptune to form Whistler.
Whistler	Windows 2002	Windows XP	Named after Whistler Blackcomb, where design retreats were held.
Mantis	—N/a	Windows XP Embedded	Named after the Mantis shrimp.
Freestyle	—N/a	Windows XP Media Center Edition	—N/a
Harmony	—N/a	Windows XP Media Center Edition 2004	—N/a
Symphony	—N/a	Windows XP Media Center Edition 2005	—N/a
Slalom	—N/a	Dropped	Longhorn Media Center Edition. Scrapped in favor of including Windows Media Center in Home Premium and Ultimate editions instead of a dedicated Media Center edition.
Emerald	—N/a	Windows XP Media Center Edition 2005 Update Rollup 2	—N/a
Diamond	—N/a	Windows Media Center	Included with Windows Vista.
Springboard	—N/a	—N/a	Set of enhanced security features, included in Windows XP Service Pack 2.
Lonestar	—N/a	Windows XP Tablet PC Edition 2005	—N/a
Whistler Server	Windows 2002 Server, Windows .NET Server, Windows .NET Server 2003	Windows Server 2003	—N/a
Bobcat	—N/a	Windows Small Business Server 2003	Not to be confused with Microsoft Bob.
Eiger, Mönch	—N/a	Windows Fundamentals for Legacy PCs	Mönch included additional features for use on mobile devices.
Longhorn	—N/a	Windows Vista	Named after the Longhorn Bar in the Whistler Blackcomb ski resort; initially planned as a "minor release" between "Whistler" and "Blackcomb" (see below)
Blackcomb, Vienna	—N/a	Dropped	The purported successor to Whistler, and later, Longhorn. Named after Whistler Blackcomb, where design retreats were held. Blackcomb was later renamed to Vienna in January 2006, named after the capital of Austria. Eventually cancelled due to scope creep and replaced with Windows 7.
Q, Quattro	—N/a	Windows Home Server	—N/a
Vail	—N/a	Windows Home Server 2011	—N/a
Longhorn Server	—N/a	Windows Server 2008	—N/a
Cougar	—N/a	Windows Small Business Server 2008	—N/a
Centro	—N/a	Windows Essential Business Server	Named after the Spanish translation of the word "center".
7	—N/a	Windows 7	The number 7 comes from incrementing the internal version number of Windows Vista (6.0) by one. Often incorrectly referred to as Blackcomb or Vienna, while the codenames actually refer to an earlier Vista successor project that was cancelled due to scope creep.
Windows Server 7	—N/a	Windows Server 2008 R2	—N/a
Solution Server	—N/a	Windows MultiPoint Server 2010	—N/a
Windows MultiPoint Server "2"	—N/a	Windows MultiPoint Server 2011	—N/a
Fiji	Windows Vista Media Center Feature Pack 2008	Windows Media Center TV Pack 2008	Named after the country of Fiji.
Cascades	Windows Essential Business Server "v2"	Windows Essential Business Server 2008 R2 (cancelled)	Originally intended as the successor of Windows Essential Business Server 2008 but was cancelled "due to external factors".
Aurora	—N/a	Windows Small Business Server 2011 Essentials	—N/a
Quebec	—N/a	Windows Embedded Standard 7	Named after the province of Quebec
Windows 8	—N/a	Windows 8	Often incorrectly referred to as Jupiter, Midori and Chidori. Jupiter is the application framework used to create "immersive" apps for Windows 8, and Midori was a separate, managed code operating system. (see below)
Windows Server "8"	—N/a	Windows Server 2012	—N/a
Blue	—N/a	Windows 8.1	—N/a
Windows Server Blue	—N/a	Windows Server 2012 R2	—N/a
Threshold	Windows 8.2, Windows 9	Windows 10 Windows 10 November Update	Named after a location seen in Halo: Combat Evolved, near which Installation 04 orbits.
Redstone	—N/a	Windows Server 2016 Windows 10 Creators Update Windows 10 Fall Creators Update Windows 10 April 2018 Update Windows Server 2019	Named after a fictional mineral from Minecraft.
Santorini	Windows 10X	Dropped	Named after an island in Greece. Originally supposed to be a new OS to be released mid-late 2021, was eventually cancelled. Some of its features were integrated into Windows 11 and other products.
Sun Valley	—N/a	Windows 11	Named after Sun Valley, Idaho.
Hudson Valley	—N/a	Windows 11, version 24H2	Named after Hudson Valley, New York.

Windows platform development semesters

The following are code names used for internal development cycle iterations of the Windows core, although they are not necessarily the code names of any of the resulting releases. With some exceptions, the semester designations usually matches the Windows version number.

Codename	Semester	Release	Notes	Ref
Titanium	19H1	Windows 10 May 2019 Update	Named after the chemical element in the periodic table.
Vanadium	19H2	Windows 10 November 2019 Update	Named after the chemical element in the periodic table.
Vibranium	20H1	Windows 10 May 2020 Update Windows 10 October 2020 Update Windows 10 May 2021 Update Windows 10 November 2021 Update Windows 10 2022 Update	Named after the fictional metal Vibranium in Marvel Comics as continuing the previous line of chemical elements with Chromium could have caused confusion with the web browser project.
Manganese	20H2	—N/a	Named after the chemical element in the periodic table.
Iron	21H1