Windows 8 is the codename for the next version of the Microsoft Windows computer operating system following Windows 7. It has many changes from previous versions. In particular it adds support for ARM microprocessors in addition to the previously supported x86 microprocessors from Intel and AMD. A new Start Screen interface has been added that was designed for touchscreen input in addition to mouse, keyboard, and pen input.

In January 2011, at the Consumer Electronics Show (CES), Microsoft announced that Windows 8 would be adding support for ARM microprocessors in addition to the x86 microprocessors from Intel and AMD.

A 32-bit Milestone 1 build, build 7850, with a build date of September 22, 2010, was leaked to BetaArchive, an online beta community, which was soon leaked to P2P/torrent sharing networks on April 12, 2011. Milestone 1 includes a ribbon interface for Windows Explorer, a PDF reader called Modern Reader, an updated task manager called Modern Task Manager, and native ISO image mounting. A 32-bit Milestone 2 build, build 7927, was leaked to The Pirate Bay on August 29, 2011 right after many pictures leaked on BetaArchive the day before. Features of this build are mostly the same as build 7955. A 32-bit Milestone 2 build, build 7955, was leaked to BetaArchive on April 25, 2011. Features of this build included a new pattern login and a new file system known as Protogon. A 64-bit Milestone 3 build, build 7959, was leaked to BetaArchive on May 1, 2011. This build is notable for being the first publicly leaked Windows Server 8 build, as well as the first leaked 64-bit build. A Milestone 3 build, build 7971, was released to close partners of Microsoft on March 29, 2011 but was kept under heavy security. However, a few screenshots were leaked. The "Windows 7 Basic" theme now uses similar metrics to the Aero style, but maintains its non-hardware accelerated design, and also supports taskbar thumbnails. The boxes that encase the "close, maximize, and minimize" buttons have been removed, leaving just the signs. A 64-bit Milestone 3 build, build 7989, leaked to BetaArchive on June 18, 2011 after screenshots were revealed the previous day. An SMS feature, a new virtual keyboard, a new bootscreen, transparency in the basic theme, geo-location services, Hyper-V 3.0, and PowerShell 3.0 were revealed in this build.