| WAITS | Stanford Artificial Intelligence Laboratory | — | — |
| Wando OS | — | — | — |
| Wang VSOS | Wang Laboratories | — | — |
| WatchOS | Apple Inc. | — | — |
| WatchOS 1 | Apple Inc. | 2015 | Apple Public Source License |
| WatchOS 10 | Apple Inc. | — | — |
| WatchOS 11 | Apple Inc. | 2024 | — |
| WatchOS 2 | Apple Inc. | 2015 | Apple Public Source License |
| WatchOS 26 | — | — | — |
| WatchOS 3 | Apple Inc. | 2016 | Apple Public Source License |
| WatchOS 4 | — | 2017 | Apple Public Source License |
| WatchOS 5 | — | 2018 | Apple Public Source License |
| WatchOS 6 | Apple Inc. | — | — |
| WatchOS 7 | Apple Inc. | — | — |
| WatchOS 8 | Apple Inc. | — | — |
| WatchOS 9 | Apple Inc. | — | — |
| WattOS | — | — | — |
| Wear OS | Google | 2014 | Apache License |
| Webconverger | — | — | — |
| WebOS | LG Electronics | — | GNU General Public License, Apache License |
| WebOS Open Source Edition | — | — | Apache Software License 2.0 |
| WEGA | EAW | — | — |
| What's Your Sign? | Objective-See | — | GNU General Public License, version 3.0 |
| White Box Enterprise Linux | — | — | GNU General Public License |
| Whitix | — | — | — |
| Whonix | — | 2012 | GNU General Public License |
| Wienux | — | — | — |
| Wifislax | — | — | — |
| Wifiway | — | — | — |
| Wii system software | Nintendo | 2006 | — |
| Wii U system software | Nintendo | — | — |
| Wind River Linux | — | — | — |
| WindexOS | — | — | — |
| Windows 1.0 | Microsoft, NEC | 1985 | end-user license agreement |
| Windows 1.04 | Microsoft | 1987 | — |
| Windows 10 | Microsoft | 2015 | shareware, Microsoft Software Assurance, Azure Dev Tools for Teaching |
| Windows 10 Home | Microsoft | — | — |
| Windows 10 IoT | Microsoft | — | — |
| Windows 10 S | Microsoft | — | — |
| Windows 10 Version 1507 | Microsoft | 2015 | — |
| Windows 10 Version 1511 | Microsoft | 2015 | — |
| Windows 10 Version 1607 | Microsoft | — | — |
| Windows 10 Version 1703 | Microsoft | — | — |
| Windows 10 Version 1709 | Microsoft | 2017 | — |
| Windows 10 Version 1803 | Microsoft | — | — |
| Windows 10 Version 1809 | Microsoft | 2018 | — |
| Windows 10 Version 1903 | Microsoft | 2019 | — |
| Windows 10 Version 1909 | Microsoft | — | — |
| Windows 10, version 20H2 | Microsoft | — | — |
| Windows 10, version 21H1 | Microsoft | 2021 | — |
| Windows 10, version 21H2 | Microsoft | 2021 | — |
| Windows 10, version 22H2 | Microsoft | 2022 | — |
| Windows 10X | Microsoft | — | — |
| Windows 11 | Microsoft | 2021 | end-user license agreement |
| Windows 12 | Microsoft | — | Microsoft end-user license agreement |
| Windows 2.0 | Microsoft | 1987 | proprietary license |
| Windows 2.1 | Microsoft | — | proprietary license |
| Windows 2000 | Microsoft | 2000 | proprietary license |
| Windows 3.0 | Microsoft | — | proprietary license |
| Windows 3.1 | Microsoft | 1992 | — |
| Windows 3.1x | Microsoft | — | proprietary license |
| Windows 3.2 | Microsoft | 1993 | — |
| Windows 3.x | Microsoft | 1990 | — |
| Windows 365 | Microsoft | — | — |
| Windows 7 | Microsoft | 2009 | volume licensing, Microsoft Software Assurance, end-user license agreement |
| Windows 7 Ultimate | Microsoft | — | — |
| Windows 8 | Microsoft | 2012 | end-user license agreement |
| Windows 8.1 | Microsoft | — | end-user license agreement |
| Windows 8.1 with Bing | Microsoft | — | — |
| Windows 8.x | Microsoft | 2012 | — |
| Windows 95 | Microsoft | — | proprietary license |
| Windows 95 OSR2 | Microsoft | 1996 | — |
| Windows 97 | Microsoft | — | — |
| Windows 98 | Microsoft | 1998 | Microsoft Software Assurance, proprietary license |
| Windows 9x | Microsoft | — | — |
| Windows Azure | Microsoft | — | — |
| Windows CE 4.0 | Microsoft | — | — |
| Windows CE 5.0 | Microsoft | — | — |
| Windows CPC | Microsoft | — | — |
| Windows Embedded 8 | Microsoft | — | — |
| Windows Embedded Automotive | Microsoft | — | — |
| Windows Embedded CE 6.0 | Microsoft | 2006 | — |
| Windows Embedded Compact | Microsoft | — | end-user license agreement |
| Windows Embedded Compact 7 | Microsoft | — | proprietary license, commercial software |
| Windows Embedded Industry | — | — | — |
| Windows Embedded Standard 7 | Microsoft | — | — |
| Windows Essential Business Server 2008 | Microsoft | — | — |
| Windows for Workgroups 3.11 | Microsoft | 1993 | — |
| Windows Fundamentals for Legacy PCs | Microsoft | — | — |
| Windows Home Server | Microsoft | — | — |
| Windows Home Server 2011 | Microsoft | — | commercial software, proprietary license |
| Windows IoT | Microsoft | — | — |
| Windows Longhorn | Microsoft | — | — |
| Windows Me | Microsoft | 2000 | Microsoft end-user license agreement |
| Windows Mobile | Microsoft | — | proprietary license |
| Windows Mobile 2003 | Microsoft | — | — |
| Windows Mobile 5.0 | Microsoft | — | — |
| Windows Mobile 6.0 | Microsoft | — | — |
| Windows Mobile 6.1 | Microsoft | — | — |
| Windows Mobile 6.5 | Microsoft | — | — |
| Windows Mobile Smartphone | — | — | — |
| Windows MultiPoint Server | Microsoft | — | shareware, Microsoft Software Assurance, Client access license |
| Windows Nashville | Microsoft | — | — |
| Windows Neptune | Microsoft | — | non-disclosure agreement |
| Windows NT | Microsoft | 1993 | — |
| Windows NT 3.1 | Microsoft | — | Microsoft end-user license agreement |
| Windows NT 3.5 | Microsoft | — | commercial software, proprietary license |
| Windows NT 3.51 | Microsoft | 1995 | proprietary license |
| Windows NT 4.0 | Microsoft | — | — |
| Windows Odyssey | Microsoft | — | — |
| Windows Phone 7 | Microsoft | 2010 | — |
| Windows Phone 8 | Microsoft | 2012 | — |
| Windows Phone 8.1 | Microsoft | 2014 | end-user license agreement |
| Windows Polaris | Microsoft | — | — |
| Windows Preinstallation Environment | Microsoft | — | freeware |
| Windows RT | Microsoft | — | — |
| Windows Server | Microsoft | — | Client access license, proprietary license |
| Windows Server 2000 | Microsoft | 2000 | — |
| Windows Server 2003 | Microsoft | — | shareware, Microsoft Software Assurance, Client access license |
| Windows Server 2003 R2 | Microsoft | — | shareware, Microsoft Software Assurance, Client access license |
| Windows Server 2008 | Microsoft | — | Microsoft Software Assurance, shareware, Client access license |
| Windows Server 2008 R2 | Microsoft | — | shareware, Microsoft Software Assurance, Client access license |
| Windows Server 2012 | Microsoft | — | end-user license agreement, Client access license, Microsoft Software Assurance, shareware |
| Windows Server 2012 R2 | Microsoft | — | Microsoft Software Assurance, Client access license, shareware |
| Windows Server 2016 | Microsoft | — | end-user license agreement, Microsoft Software Assurance, Client access license |
| Windows Server 2019 | Microsoft | — | — |
| Windows Server 2022 | Microsoft | — | — |
| Windows Server 2025 | Microsoft | 2024 | proprietary license |
| Windows Small Business Server 2003 | Microsoft | — | — |
| Windows Small Business Server 2008 | Microsoft | — | — |
| Windows Thin PC | Microsoft | — | — |
| Windows Vista | Microsoft | — | end-user license agreement |
| Windows Vista Starter | — | — | — |
| Windows XP | Microsoft | — | volume licensing, shareware, Microsoft Software Assurance |
| Windows XP 64-Bit Edition | Microsoft | — | — |
| Windows XP Embedded | — | — | Microsoft end-user license agreement |
| Windows XP Media Center Edition | Microsoft | — | — |
| Windows XP Professional | — | — | — |
| Windows XP Professional x64 Edition | Microsoft | — | volume licensing, commercial software, Microsoft Software Assurance, shareware |
| Windows XP Tablet PC Edition | Microsoft | — | — |
| Windows 10 Mobile | Microsoft | 2015 | — |
| Winux | — | — | — |
| Wireless identification and sensing platform | — | — | Creative Commons license |
| Wolvix | — | — | — |
| Wombat OS | — | — | GNU General Public License |
| Woof | — | — | — |