Windows Update

Windows Update is a free updating service by Microsoft that regularly give updates to Windows and other Microsoft products, sometimes also for drivers. It is used to keep Microsoft apps and the Windows operating systems updated and often protected from malware and ransomware.

Windows XP, Server 2003 and earlier
Windows Update was launched as a web service using Internet Explorer technologies with the release of Windows 98. Previously, it was included since build 1351 as "Internet System Update". It was ported to the NT line of Windows with the Windows 2000 Beta 3.

It works by installing an ActiveX control element, which allows installing updates directly from Internet Explorer. The web service for Windows 98 and Me was shut down in the early 2010s, while Windows 2000 was updated to use Windows XP's web service, which itself, alongside with Vista's update service was shut down in 2020 due to Microsoft updating their security to use the SHA-256 algorithm, which is not supported by Windows versions earlier than Windows 7. Windows 7 requires an update released in 2018 which introduces SHA-256 support, which caused the system requirements to be raised up to a processor with the SSE2 instruction.

All released updates for Windows, Office and other Microsoft products are still available at the Microsoft Update Catalog.

Windows Vista, Server 2008 and later
In Windows Vista (since build 5259), Windows Update was overhauled to have an own Control Panel applet, rather than being based on a web service. In Windows 10 (since build 9900), Windows Update was moved to the Settings app.

Location

 * In Windows 98 through to XP, it is located in Internet Explorer.
 * In Windows Vista through to 8.1, it is located in the Control Panel.
 * In Windows 8 through to 11, it is located in the Settings app.

Patch Tuesday
Patch Tuesday is a day where Microsoft releases patches and security updates for Windows routinely, usually being the second Tuesday of every month. However, Microsoft still releases urgent updates on most other days. However, for enterprise customers with Windows 10 or 11 E3 licenses, Microsoft is about to stop releasing patches on these days in favor of automatic patches (Windows Autopatch).

Automatic Updates
Formerly known as the Windows Critical Update Notification Tool in Windows 98 and 2000, this tool runs in the background and notifies the user when a critical update is available. In Windows Me (9x) and Windows XP / 2000 SP3 (NT), this tool was replaced with Automatic Updates (codenamed Windows AutoUpdate). Automatic Updates will not require a web browser, and checks updates less routinely than the Critical Update Notification Tool.

Filetypes
On XP and earlier, updates were either packed in executables or in cabinet archives. Windows Vista uses,   and   file extensions on the updates. Also, standalone updates are now packed in  archives, which are opened by. These archives still have updates packed in cabinet archives. Windows 11 additionally uses  files.

Repair Content Packages
In Windows 8 build 8250, the ability to repair a Windows installation using Windows Update was added. This was initially achieved by the use of Repair Content Packages, which contain all packages for a build of Windows (similar to an unstaged ISO, including all client and server SKUs including MinWin-based SKUs, and packages no longer included in any shipping edition but nonetheless still built like the Windows 7 games). These package sets were superseded in RS3 by the Unified Update Platform (UUP).

Windows 10 and 11 feature updates

 * See Windows 10 updates and Windows 11 updates for the subsequent feature updates released for Windows 10 and Windows 11.