Windows Update is a proprietary update mechanism for Microsoft's Windows line of operating systems.

For all versions of Windows 95 and up, anybody can visit the Windows Update website and download updates tailored towards their system. In this respect, Windows Update is much like the Linux equivalents of APT and Portage. However, Windows Update is purely for software patches: it does not allow the downloading of third party software.

Windows Update does not work like a normal web page: it works through Microsoft's ActiveX scripting model, which is why you are asked to install something on your first visit. Unfortunately, because the system works through ActiveX it is not available through browsers other than Internet Explorer, such as Mozilla Firefox, requiring users of these browsers to download .exe files manually from the Microsoft website, a painstaking and time-consuming process.

Upon installing the ActiveX control and entering the website, users are asked to scan for updates. They are then presented with a list of updates for their system organised into categories. These categories are:

  • Critical Updates - Essential updates related to security or bad functionality
  • Windows xx - Microsoft addons onto the Windows operating system, where xx is the Windows version.
  • Driver Updates - Updates to Windows certified drivers. This is not updated very often and does not have a very wide selection of drivers.

On selecting the updates they require using an HTML form, the user is taken to a confirmation page and eventually a standard Windows window pops up showing download status and completion. When the updates are completely downloaded, they are automatically installed. While they are downloading, the user cannot use Internet Explorer to browse to other websites: they must open up another browser or create a new window, otherwise the download will fail.

On Windows XP it is no longer necessary to go to the Windows Update website regularly, as the OS downloads updates automatically in the background, but prompts before they are installed.