Windows codenames

Windows 3.1x/9x

Codename	Preliminary name	Final name	Notes
Janus		Windows 3.1, Windows 3.11, and Windows 3.2
Kato (Winball), Sparta (Jastro)		Windows for Workgroups 3.1
Snowball (LB)		Windows for Workgroups 3.11
Cougar		Windows for Workgroups 3.2	Same codename as Windows Small Business Server 2008
Chicago 9x (95 Pre-Release)	Windows 4.0	Windows 95	Same codename as Windows 7.1
O'Hare		Internet Explorer, first shipped in Microsoft Plus! for Windows 95	O'Hare is the main airport for the city of Chicago.
Frosting		Microsoft Plus! for Windows 95
Detroit		Windows 95 Service Pack 2
Cleveland, Nashville	Windows 4.1	Windows 96
Memphis	Windows 4.2, Windows 97	Windows 98	The codename was the key to activating an easter egg in Windows 98: open the "Date and Time" control panel; go to the "Timezone" page; hold the Control key and drag a line with the mouse cursor from Memphis, Egypt (or maybe Cairo, the 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.
Dolly		Windows 98 OEM/Corporate image cloning utility	Dolly refers to Dolly the Sheep, the first sheep to be cloned.
Millennium	Windows 4.9	Windows Me	Me stands for Millennium Edition

Windows NT family

Codename	Preliminary name	Final name	Notes
AXP		Windows NT 3.1
Razzle		Windows NT for Workgroups 3.1, Windows NT for Workgroups 3.11
NT OS/2	OS/2 3.0	Windows NT 3.11
NT 3.2		Windows NT 3.2
Daytona		Windows 3.5x
Cairo		N/A	Never released.
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 3.51's kernel.
Wolfpack		Microsoft Cluster Server
Hydra	Terminal Services, Terminal Server	Windows NT 4.0 Terminal Server	Terminal Server adds "multithreading" support to Windows (the ability to run multiple instances of the graphics subsystem), and the Lernaean Hydra is a mythological monster with multiple heads.
Impala	Windows NT 4.1	Windows NT 4.0 Embedded
Memphis, NT 5.0		Windows NT 5.0
Memphis	Windows 5	Windows 2000	Same codename as Windows 98
Memphis Server, Server 5		Windows NT 5.0 Server, Windows Server 2000
Asteroid	Windows NT 5.0 Service Pack 1	Windows 2000 Service Pack 1
Janus	Windows NT 5.0 64-bit	Windows 2000 64-bit	Same codename as Windows 3.1
Odyssey		N/A	Ideas project, merged to Whistler.
Neptune		N/A	Ideas project, merged to Whistler.
Whistler	Windows 5.1, Windows 101, Windows 2001, Windows .NET 2001, Windows NT XP	Windows XP	Merge of Whistler build 2202, Neptune and Project Odyssey. Named after Whistler, British Columbia, where design retreats were held.
Mantis		Windows XP Embedded
Creekside		Windows XP Starter
Trident		Windows XP Media Center Edition
eHome		Windows XP Media Center Edition 2002
Freestyle		Windows XP Media Center Edition 2003	Name of a terrain rating system in the Whistler-Blackcomb resort.
Harmony		Windows XP Media Center Edition 2004	Name of a ski lift and alpine bowl in Whistler, British Columbia.
Symphony		Windows XP Media Center Edition 2005	Name of an alpine bowl in Whistler, British Columbia.
Emerald		Windows XP Media Center Edition 2006	Name of a ski lift in Whistler, British Columbia.
Trainyard		Windows XP Service Pack 1	Trainyard was an engineering package of driver updates to ship simultaneously with Windows XP Service Pack 1, the most major of which was support for USB 2.0 which was also ported backwards to Windows 2000.
Springboard		Windows XP Service Pack 2	Name of a ski run on Blackcomb in Whistler, British Columbia.
Whistler Server	Windows XP Server, Windows .NET Server, Windows Server 2002	Windows Server 2003	One of many unrelated Microsoft projects of the time to carry a ".NET" designation. See: Microsoft .NET.
Bobcat		Windows Small Business Server 2003	Bobcat is a ski-run on Whistler Mountain.
Whistler Server R2	Windows Server 2005	Windows Server 2003 R2
Eiger		Windows Fundamentals for Legacy PCs	Software Assurance program. The Eiger is a mountain in the Bernese Oberland in Switzerland. The Eiger is part of a trio of mountains, The Eiger, The Mönch and The Jungfrau.
Mönch		Windows Mobile 6	VPN-s and advanced IP (Internet Protocol) security. The Mönch is a mountain in the Bernese Oberland in Switzerland. The Mönch is part of a trio of mountains, The Eiger, The Mönch and The Jungfrau.
Longhorn	Windows 6	Windows Vista	Went gold (RTM) on 8 of November 2006. Named after the Longhorn Bar in the Whistler-Blackcomb resort; initially planned as an "interim release" between "Whistler" and "Blackcomb" (which was "Vienna" and is now Windows 7).
Q, Quattro		Windows Home Server	Announced at CES 2007. Original project codename was "Quattro" because it was the leader of the project's 4th attempt at building a home server at Microsoft. Renamed to Q once the project moved out of incubation stage.
Cougar	Windows Longhorn Small Business Server	Windows Small Business Server 2008	Same codename as Windows for Workgroups 3.2. Cougar is a ski-run on Whistler Mountain.
Longhorn Server, Server 6	Windows Server 2007	Windows Server 2008	In development. Planned server equivalent of Windows Vista to be released in 2008.
Blackcomb, Vienna, Seven		Windows 7	Originally codenamed "Blackcomb" after the Whistler-Blackcomb resort. Renamed to "Vienna" in January 2006.
Longhorn Server R2, Server 7	Windows Server 2009	Windows Server 2008 R2	In development. Planned "mid-size" (25-500 PC) edition of Longhorn Server.[1].
Chicago NT (Windows 7.1 Pre-Release)		Windows 7.1	Same codename as Windows 95
Longhorn Server R3, Server 7.1	Windows Server 2010	Windows Server 2008 R3
Vail		Windows Home Server 2011
Jupiter, Eight		Windows 8
Server 8		Windows Server 2012
Metro		Windows 8 Style UI	Renamed from Metro because of a lawsuit with the German Metro company
Blue		Windows 8.1
Server Blue, Server 8.1	Windows Server 2013	Windows Server 2012 R2
Threshold	Windows 9	Windows 10
Threshold 2		Windows 10 November Update
Threshold Server	Windows Server 2015	Windows Server 2016
Redstone		Windows 10 Anniversary Update	Redstone is a mineral and item in Minecraft, a game product by Mojang and Microsoft bought it in 2015
Redstone 2		Windows 10 Creators Update
Redstone 3		Windows 10 Fall Creators Update
Redstone 3 Server		Windows Server version 1709
Redstone 4	Windows 10 Spring Creators Update	Windows 10 April 2018 Update
Redstone 4 Server		Windows Server version 1803
Redstone 5		Windows 10 October 2018 Update
Redstone 5 Server	Windows Server 2016 R2	Windows Server 2019, Windows Server version 1809
19H1		Windows 10 May 2019 Update
19H1 Server		Windows Server version 1903
19H2		Windows 10 19H2
19H2 Server		Windows Server 19H2
20H1		Windows 10 20H1
20H1 Server		Windows Server 20H1