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.

Web Service
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 (since build 2031.1).

It works by installing an ActiveX control element, which allows installing updates directly from Internet Explorer. The web service for Windows 98 and Windows Me was shut down in 2011, while Windows 2000 was updated to use Windows XP's web service, which itself, alongside with Windows 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.

Control Panel
In Windows Vista (since build 5259), Windows Update was overhauled to have it's own Control Panel applet, rather than being based on a web service.

Windows Update also added the ability for users of the Ultimate edition of Windows Vista to download Windows Ultimate Extras.

The applet was slightly redesigned in Windows 7, which would later be backported to Windows Vista.

Settings
In Windows 8 (since build 7978), Windows Update was added to PC Settings. It was a simpler alternative to the existing Control Panel applet. The UI would receive more options in Windows 8.1.

In Windows 10 (since build 9900), Windows Update was officially moved to the Settings app. As a result, the Control Panel applet was deprecated (but can be restored up to build 10041).

Windows Update received major changes to its operations and functionality and it no longer allows the manual, selective installation of updates. All updates, regardless of type (this includes hardware drivers), would be downloaded and installed automatically, and users are only given the option to choose whether their system would reboot automatically to install updates when the system is inactive, or be notified to schedule a reboot.

Microsoft offers a diagnostic tool that can be used to hide troublesome device drivers and prevent them from being reinstalled, but only after they had been already installed, then uninstalled without rebooting the system.

It also added the ability to perform peer to peer distribution of updates. By default, systems' bandwidth is used to distribute previously downloaded updates to other users, in combination with Microsoft servers. Users may optionally change Windows Update to only perform peer to peer updates within their local area network.

Windows 10 introduced cumulative updates which packages seperate updates into a single update package, mitigating the need for multiple restarts and reducing the number of downloads needed. This meant that it was no longer possible to download and install updates that fix individual problems. Cumulative updates would later be backported to Windows 7 and Windows 8.1 in October 2016.

Originally, all updates would be installed automatically when users checked for updates. Starting with Windows 10 May 2019 Update, the ability for users to delay the installation of updates up to 35 days was added to the Home SKUs. Also, Microsoft made major changes to how feature updates were rolled out to users and instead, rolling out the update to a select group of users before rolling it out to all users.

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). Starting from Windows 10, many more languages are included compared to previous versions (including both regular and mirrored pseudolocalisation). Starting from RS1, only packages for released client and server SKUs are included (MinWin-based SKUs and unreleased SKUs are no longer present). These package sets were superseded in RS3 by the Unified Update Platform (UUP).