Windows 11 build 21327

Not to be confused with Windows 10 build 21327.

Windows 11 build 21327 is the earliest known build of Windows 11. It was mentioned in an issue posted to Visual Studio's Developer Community by a Microsoft employee on 11 March 2021. As the build tag is repeated multiple times throughout the thread, it is unlikely that it is a typo of 21327.1000.rs_prerelease.210226-1437.

This build is one out of two known builds to be compiled from a branch with the  prefix, the other being build 21380. The prefix stands for Fire Steel, the codename for an internal Microsoft tool related to Windows 11 development.