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Windows codenames are the codenames given by Microsoft to Windows 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 prior to 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 so as to avoid needing product codenames.

Windows (DOS-based)

Codename(s) Preliminary name Final name Notes Ref
Interface Manager Windows 1.0
N/A Windows 1.5 Windows 2.0 Per antitrust documents.
N/A Windows 3.0
Janus Windows 3.1 Windows 3.11, and Windows 3.2 (China only, 1994) Same codename as Windows 2000 64-bit
Sparta (Kato), Winball (Jastro) Windows 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 Windows for Workgroups 3.11 Although this release was still 16-bit Windows, it included a 32-bit TCP/IP stack (when running on compatible hardware). Along with Win32s, this was one of the first steps towards moving the Windows desktop to a 32-bit code base.
Cougar Windows/WFW "3.2\ VMM32.exe in Win9x Pre-Win95 project from 1992. Goal was to add a 32-bit virtual memory manager to Windows 3.1. Versions were internally dubbed "Windows 3.2".
Cougar, Chicago Windows 4.0 Windows 95
O'Hare Internet Explorer, first shipped in Microsoft Plus! for Windows 95 The codename O'Hare ties into the Chicago codename for Windows 95: O'Hare International Airport is the largest airport in the city of Chicago — in Microsoft's words, "a point of departure to distant places from Chicago".
Frosting Microsoft Plus! for Windows 95
Detroit Windows 95 OSR 2 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.
Cleveland, Nashville Windows 96
Memphis Windows 4.1, Windows 97 Windows 98 The codename was the key to activating an easter egg in Windows 98:
  • Open the "Regional Settings" control panel;
  • Go to the "Regional Settings" page;
  • Hold the Control key and drag a line with the mouse cursor from Memphis, Egypt (or maybe Cairo, codename of Windows NT 4 - the map is too small to tell) to Memphis, Tennessee. Still holding the Control key, drag another line from Memphis to Redmond, Washington;
  • A window opens with the credits for Windows 98.
  • this codename is also visible from Windows 95 OSR in its version of DOS 7 - before any EXEs or windows is loaded the words: Microsoft (R) Memphis - are loaded into memory, although on the disc they are encrypted.
Millennium Windows 4.9 Windows Me Millenium Edition

Windows NT family

Codename Preliminary name Final name Notes
Razzle NTOS, later NT OS/2 Windows NT 3.1 Originally OS/2 3.0 before 1990
Daytona Windows NT 3.5 and Windows NT 3.51 Named after the Daytona International Speedway in Daytona Beach, Florida.
SUR (Shell Update Release) Windows NT 4.0 Microsoft originally planned for NT 4.0 to be just a simple "Shell Update Release" to integrate the Windows 95 GUI with Windows NT 3.51's kernel.
Cairo Never released Microsoft project undergone from 1991 to 1996. Many features planned - for example, a brand new UI and an object oriented file system. Never released, although most of the technologies sans the object-oriented file system shipped as part of Win95 or WinNT. Later attempts at an object oriented file system by Microsoft include scrapped features for MS SQL Server 98 and 2000, WinFS for Longhorn, developed from 1999 to 2006, and the Microsoft Semantic Engine, developed until at least November 2009. Two known leaked builds, one further known build.
Wolfpack Microsoft Windows NT Cluster Server 4.0
Hydra Windows NT 4.0 Terminal Server Terminal Server adds "multiheading" support to Windows (the ability to run multiple instances of the graphics subsystem), and the hydra is a mythological monster with multiple heads.
Janus Windows 2000 64-bit Same codename as Windows 3.1x
Impala Windows NT 4.0 Embedded
Neptune Never released Never released, cancelled in January 2000. One known leaked build.


Never released "NT6" planned from 1997-2000
Whistler Windows XP Named after Whistler, British Columbia, where design retreats were held.
Mantis Windows XP Embedded Named after the Mantis shrimp
Freestyle Windows XP Media Center Edition
Harmony Windows XP Media Center Edition 2004
Symphony Windows XP Media Center Edition 2005
Emerald Windows XP Media Center Edition 2005 Update Rollup 2
Diamond Windows Media Center Included in Windows Vista
Springboard Set of enhanced security features, included in Windows XP Service Pack 2.
Lonestar Windows XP Tablet PC Edition 2005
Whistler Server Windows .NET Server,

Windows .NET Server 2003

Windows Server 2003
Whistler Small Business Server Windows Small Business Server 2003
Eiger, Mönch Windows Fundamentals for Legacy PCs Mönch included additional features for use on mobile devices.
Whistler Server R2 Windows Server 2003 R2
Longhorn Windows Vista Whistler-Blackcomb resort; initially planned as an "interim release" between |"Whistler" and "Blackcomb" (which was "Vienna").
Quattro Windows Home Server
Vail Windows Home Server 2011
Longhorn Server Windows Server 2008
Cougar Windows Small Business Server 2008 Same codename as VMM32
Viridian Hyper-V Virtualization update for Windows Server 2008.
Centro Windows Essential Business Server
7[1] Windows 7
Longhorn Server R2, Server 7 Windows Server 2008 R2
Fiji Windows Vista Media Center Feature Pack 2008 Windows Media Center TV Pack 2008
Red Dog Windows Cloud Windows Azure Windows cloud services platform
Aurora Windows Small Business Server 2011 Essentials
Quebec Windows Embedded 2011
Midori Windows 8
Blue Windows 8.1
Threshold 1 Windows 9 Windows 10 TH1/1507 (initial release)
Threshold 2 Windows 10 1511 TH2/1511 (November Update)
Redstone 1 Windows 10 1607 RS1/1607 (Anniversary Update)
Redstone 2 Windows 10 1703 Creators Update
Redstone 3 Windows 10 1709 Fall Creators Update
Redstone 4 Windows 10 1803 April 2018 Update
Redstone 5 Windows 10 1809 October 2018 Update
19H1 Windows 10 19H1 April 2019 Update
Vanadium Windows 10 19H2 November 2019 Update
Vibranium Windows 10 20H1 May 2020 Update
Manganese Windows 10 20H2 October 2020 Update
Iron Windows 10 21H1 May 2021 Update
Cobalt, Sun Valley Windows 11 21H2 October 5, 2021 (initial release)
Nickel, Sun Valley 2 Windows 11 22H2 Second half of 2022 (previously 22H1)[2]
Copper Windows 11 23H2 Second half of 2023 (previously 22H2)[2]

Windows CE family

Codename Preliminary name Final name Notes
Pegasus, Alder Windows CE 1.0 (released November 1996)
Birch, Gryphon Windows CE 2.1
Cedar, Galileo, Rapier, Merlin, Stinger Windows CE 3.0 (released April 2000)
Talisker Windows CE .NET Windows CE 4.0 (released January 7, 2002)
Macallan Windows CE 5.0 (released July 9, 2004)
Yamazaki Windows CE 6.0 Windows Embedded CE 6.0

Visual Studio family

Codename Preliminary name Final name Notes
Thunder Visual Basic 1.0 The first version of Visual Basic. The standard dialogs and controls created by the Visual Basic runtime library all have "Thunder" as a prefix of their internal type names (for example, buttons are internally known as ThunderCommandButton).
Zamboni Microsoft Visual C++ 4.1 After Zamboni, an ice resurfacing machine.
Boston Microsoft Visual Studio 97 Named after Boston, Massachusetts.
Aspen Microsoft Visual Studio 6.0 Named after the popular ski destination Aspen, Colorado.
Cassini Web Server ASP.NET Development Server The lightweight local Web server that is launched in Visual Studio in order to test Web projects.
Hatteras Visual Studio Team System's Source Control System Named after the Cape Hatteras Lighthouse in the Outer Banks region of North Carolina.
Ocracoke Visual Studio Team System load testing suite Named after the Ocracoke Island Lighthouse on Ocracoke Island, also in North Carolina.
Currituck Team Foundation Work Item Tracking Named after the Currituck Beach Lighthouse in Corolla, North Carolina.
Bodie Team Foundation Server SDK Named after the Bodie Island Lighthouse in North Carolina.
Tuscany Online version of Visual Studio. Currently a research project.
Phoenix A Microsoft research software development kit.
Eaglestone Visual Studio Team Explorer Everywhere This is the name given to the Teamprise suite Microsoft acquired. The product is now named Visual Studio Team Explorer Everywhere
KittyHawk Visual Studio LightSwitch RAD tool aimed at non-programmers.
Rainier Visual Studio .NET (2002) Named for Mount Ranier, a volcanic mountain peak visible from the Seattle area (where Microsoft is based).
Everett Visual Studio .NET 2003 Named after the town Everett, Washington in Washington state.
Whidbey Visual Studio 2005 Named after Whidbey Island in the Puget Sound
Orcas Visual Studio 2008 Named after Orcas Island in the Puget Sound
Dev10 Visual Studio 2010
Rosario Visual Studio Ultimate 2010 (formerly Team System or Team Suite)

SQL Server family

Codename Preliminary name Final name Notes
Sphinx SQL Server 7.0
Yukon SQL Server 2005 (Version 9)
Katmai / Akadia SQL Server 2008 (Version 10)
Kilimanjaro SQL Server 2008R2 (Version 10.5)
Plato Olap Services 7.0 This was the first release of Microsoft Analysis Services
Blue SQL Report Designer 2.0 This is the stand alone release of the tool for SQL Server Reporting Services.
Denali SQL Server 2012 (Version 11)
Juneau SQL Server Data Tools Will be included in the next CTP of SQL Server "Denali"
Crescent Power View A data visualization tool that will be included in SQL Server "Denali"

Other server products

Codename Final name Ref
Hermes Microsoft System Management Server 1.0
Catapult Microsoft Proxy Server 1.0
Geneva Active Directory Federation Services

Experimental operating systems

Codename Preliminary name Final name Notes
Singularity Singularity Experimental operating system based on the Microsoft .NET platform, using software-based type safety as a replacement for hardware-based memory protection.


Codename Preliminary name Final name Notes
Lightning, Project 42 Next Generation Windows Services Microsoft .NET v1.0 Project Lightning was the original codename for the Common Language Runtime in 1997. The team was based in building 42, hence Project 42. "Next Generation Windows Services" appeared in the earliest press releases about the upcoming platform.
Roslyn Next Generation C# compiler Unspecified, speculative to Microsoft .NET v5 or .NET v6 compiler Roslyn is the next generation of design guidelines for developer tools, which is often highlighted by a C# compiler being written in C# (currently it is C++) and being offered as a service. This would enable scenarios like C# having its own version of the JavaScript eval command ultimately leading to meta-programming. Mono has had a similar feature since early on its life
Project 7 Codename for early .net academic recruiting program. 7 was a prime factor of 42.

Xbox and Xbox 360

Codename Preliminary name Final name Notes Ref
DirectX Box Project Dakota Xbox The original codename for the Xbox.
Natal Project Natal Kinect Motion sensitive control system.
Xenon Xbox 2 Xbox 360
Durango Xbox 720 Xbox One


Codename Preliminary name Final name Notes
Acropolis Application framework for Smart Clients
Aero Diamond Used during the development of Windows Vista to describe a set of advanced user interface effects for the Desktop Window Manager to be introduced after Vista's release.
Albany Microsoft Equipt Albany is Microsoft's all-in-one, subscription-based service for office, communication, and security software.
Alexandria Zune Marketplace An online music store.
Argo Zune A digital media player.
Atlanta A cloud service that monitors Microsoft SQL Server deployments
Atlas ASP.NET AJAX An implementation for ASP.NET of Ajax native to the .NET Framework 2.0.
Avalon Windows Presentation Foundation Graphical subsystem released as part of .NET Framework 3.0.
Bandit Schedule+ 1.0 Microsoft's first Personal Information Manager.
Blackbird An online content-authoring platform centered around the concept of distributed OLE (Object Linking and Embedding) and meant to be an alternative to HTML. The developer tools were originally released in beta and some titles were made available on MSN before it was scrapped in favor of web development around ASP and ActiveX and the designer was refashioned into Visual InterDev.
Marvel The Microsoft Network The classic version of MSN, originally as a proprietary, "walled garden" online service.
Bullet Microsoft Mail 3.0 Microsoft's first LAN-based email product written in-house. (Microsoft had earlier purchased Intermail for AppleTalk networks and Network Courier for PC networks.)
Budapest Microsoft Office Communicator Web Access 2005
Catapult Microsoft Proxy Server 1.0
Cashmere, Opus Microsoft Word for Windows Developed 1984-1989 per antitrust docs
Cider Visual Studio designer for building Windows Presentation Foundation applications. Meant to be used by application developers.
Cirrus Access 1.0
Concur Aims to: define higher-level abstractions (above "threads and locks"); for today’s imperative languages; that evenly support the range of concurrency granularities; to let developers write correct and efficient concurrent applications; with lots of latent parallelism; that can be efficiently mapped to the user’s.
CRM V1.0, Tsunami Microsoft CRM version 1.0 The platform was initially code named Tsunami, but once the decision was made to make it an actual product it was just changed to the initials as the initials were enough of a code name.
D M Modelling language
Dallas Easily discover, purchase, and manage premium data subscriptions in the Windows Azure platform.
Darwin Microsoft Installer Windows Installer
Danube Phase I Microsoft CRM version 1.2
Danube Phase II Microsoft CRM version 3
Deco Microsoft PhotoDraw
Dorado Zune PC Client
Dryad A Microsoft Research project which aims to design a platform to make developing applications for large-scale distributed computing easier.
Godot Microsoft Layer for Unicode Named after the play Waiting for Godot (centered around the failure of a man named "Godot" to appear and the endless wait for him), because it was felt to be long overdue.
Greenwich Real-Time Communications Server 2003 Microsoft Office Live Communications Server 2003
Indigo Windows Communication Foundation An application programming interface (API) in the .NET Framework for building connected, service-oriented applications
Istanbul Microsoft Office Communicator 2005
Kumo Bing Microsoft's set of features improving Live Search search engine
Clarity LINQ Language Integrated Query Language extensions to expose query syntax natively to languages such as Visual Basic .NET and C#
Maestro Microsoft Office Business Scorecard Manager 2005.
Media2Go Windows Mobile software for Portable Media Centers Platform built on Windows Mobile found on portable media players.
Metro XML Paper Specification (XPS)
Milan Microsoft Surface Table-top style computer with multi-touch touchscreen interface.
Mira Windows CE .NET-based technology for smart displays.
Monaco Music-making program similar to Apple's GarageBand application
Monad MSH, Microsoft Shell Windows PowerShell Monads, according to philosopher Gottfried Leibniz's monadology, are the ultimate elements of the universe, individual percipient beings, and MSH is similarly composed of small, individual modules the user puts in interrelation.
Morro Microsoft Security Essentials MSE was codenamed after the Morro de São Paulo beach.
Origami Ultra-Mobile PC
Omega JET Engine ISAM database engine used in Microsoft Access, a desktop database management system.
Opus Word for Windows Word for Windows 1.0 for Windows 2.x, named after the penguin in the comic strip Opus.
Palladium Trusted Windows Effort to develop a small, very secure operating environment within Windows, including curtained memory, trusted input, and graphics. Project renamed to Next-Generation Secure Computing Base, and was never fully implemented.
Pinball High Performance File System Implemented as an Installable File System when IBM and Microsoft were co developing OS/2.
Volta C# to JavaScript compiler.
Softsled Software based Media Center Extender.
Springfield Microsoft Popfly Website in Alpha testing stage providing mashup and webpages creation tools, with publishing as Rich Internet Application option.
Tahiti Supposedly a family of multi-core technologies including an operating system, applications and development tools designed to make better use of today's multi-core CPUs. It is believed that Midori may be a part of this suite of new Microsoft technologies.
Tahiti Microsoft SharedView A screen sharing tool which allows users to take over sessions and interact with remote desktops. No audio or conference facilities.
Tahoe Sharepoint Portal Server 2001.
Titan, Kilimanjaro Microsoft CRM version 4 Was originally Kilimanjaro but changed to Titan as Kilimanjaro was too difficult to spell.
Jakarta Visual J++
Jasper “Jasper” provides a programming interface to your data that is well-suited to rapid development. When a Jasper program runs, Jasper connects to the database, determines the database schema, and generates corresponding data classes. This generation step does not result in source files; the data classes are compiled in-memory and available for use within the running program.
Jolt Silverlight 1.0
Paxos Silverlight 1.1
Wolverine TCP/IP Stack for WfW 3.11 Named after the Wolverine the character from Marvel Comics.
Oslo set of SOA - technologies
Velocity Distributed Caching for .NET
Zurich Azure Microsoft's Cloud platform (See Azure Services Platform)
Metro Windows Phone 7 user interface, largely based on Zune HD
Mango Windows Phone 7.5 Windows Phone 7, largely based on Zune HD


  1. What was the code name for Windows 7? by Raymond Chen, Microsoft. 2019-07-22.
  2. 2.0 2.1 Windows 11 22H2 is almost cooked suggests a leaked internal script for Insiders by Sayan Sen, NeoWin. 2022-01-24.

External links