Windows 8.1

Windows 8.1 is an operating system by Microsoft. It is a free upgrade for all Windows 8 users. It replaces Windows 8 and was succeeded by Windows 10 on 29 July 2015. Although the operating system was marketed by Microsoft as an update for Windows 8, Microsoft's traditional support policy treats Windows 8.1 as a service pack.

Mainstream support ended on 9 January 2018, while extended support ended on 10 January 2023. Windows 8 users were given the option to upgrade to Windows 8.1 in order to receive support within 2 years since its release. Despite being out of support, the operating system is still used on 2.28% of computers worldwide as of January 2023.

It is the last release of Windows to have support for Windows Media Center as Microsoft discontinued support for the application with the release of Windows 10. It is also the last release of Windows to have the ability to create MS-DOS 8.00 startup disks, and thus to include MS-DOS in any form and to ship with a DVD release at retail, since physical retail copies of Windows 10 and later ship with a USB flash drive (although some OEMs still shipped some versions of Windows 10 on DVD).

RTM

 * The Start button was brought back (although it still leads to the Metro start screen).
 * The "All Apps" view was added to the Start screen.
 * Added Device Encryption for compatible hardware.
 * Added support for 3D printing.
 * The snapping functionality for Metro apps was updated.
 * Added new sizes for Start screen titles.
 * Internet Explorer 11 was introduced. The Metro UI version also received some updates.
 * Introduced Assigned Access which allows the computer to be locked to running a single Metro app.
 * Changes to the search function.
 * Photo slideshows can now be displayed on the lock screen.
 * Windows Store received an updated user interface and added the ability for apps to automatically update.
 * Added support for Wi-Fi Direct, Miracast, tethering and NVMe.
 * Text and GUI elements can now scale up to 200%. Additionally, scaling settings can now be setup independently on each display in multi-monitor configurations.
 * Computer is renamed to This PC.
 * Clicking the File Explorer icon in the taskbar will take the user to This PC instead of Libraries, unlike in Windows 7 and 8. Additionally, Libraries are disabled by default, but it can be re-enabled by right-clicking on the navigation pane and choosing "Show libraries" or "Show all folders".
 * User folders (Desktop, Documents, Downloads, Music, Pictures, Videos) added to This PC.
 * The Windows Experience Index has been removed. However, the command-line tool to determine the rating values (WinSAT) is still included.
 * The Backup and Restore Control Panel applet has been removed in favor of File History.
 * Several features from Windows Easy Transfer have been removed such as the ability to start new transfers directly, the ability to transfer data from Windows XP and Windows Vista and the ability to use the Easy Transfer Cable and network connection transfer methods.
 * New set of default wallpapers.
 * The ability to shutdown the operating system by dragging the lock screen image toward the bottom of the screen was added.
 * New customization options for the Start screen.
 * New Metro applications introduced, with many existing ones updated.
 * Redesigned PC Settings.

Update 1

 * When the user hovered over the top of a Metro app, a title bar appears with minimize and close buttons.
 * Right-clicking on the Start screen opens up a menu instead of touch-oriented controls at the bottom.
 * By default, the titles for This PC, PC Settings, Documents and Pictures are pinned to the Start screen.
 * The "Go to the desktop instead of Start when I sign in" feature in Taskbar and Navigation Properties first introduced in the original release is now enabled by default.
 * Metro apps can now be pinned to the taskbar.
 * Power and Search buttons have been added to the start screen.
 * It is also possible to enable the power button on a tablet by going to  registry key, then create a new DWORD value named   and set it to 1, then restart Explorer.
 * Added dividers between apps in the "All Apps" view in Start.
 * SkyDrive was renamed to OneDrive (you can also get this in Windows 8 and Windows 8.1 RTM (without Update 1) by updating the SkyDrive app via the Store).
 * The default media player and photo viewer has been changed to Windows Media Player and Windows Photo Viewer respectively.

System requirements
Microsoft recommends Windows 8.1 to be installed on a system with a processor with a speed of at least 1 GHz, at least 1 GB (2 GB for x64 versions) of RAM, 16 GB (20 GB for x64 versions) of hard drive space, and a DirectX 9-based WDDM display adapter or better display adapter. Windows 8.1 drops support for x64 processors without the CMPXCHG16b, PrefetchW and LAHF/SAHF instructions, as attempting to boot on these processors will cause an  bugcheck.

Windows 8.1 can be installed on processors as early as the Pentium 4. The x64 version of Windows 8.1 can be installed on processors as early as the Athlon 64 with Socket AM2. Windows 8.1 can also be run with as low as 512 MB of RAM.

Hardware compatibility
Windows 8.1 is officially compatible with Intel processors up to Skylake (6th generation). On Kaby Lake (7th generation) up to Ice Lake (10th generation), 8.1 is not supported due to lack of Windows Update and Intel Graphics, however, hacks have been made to get both working. For Tiger Lake (11th generation) and Alder Lake (12th generation), no known hacks have appeared for Intel Graphics, but the chipset drivers for Ice Lake (10th generation), Tiger Lake (11th generation), and Alder Lake (12th generation) have been confirmed to install without any issues.