Windows 11 build 21380

Windows 11 build 21380 is an early build of Windows 11 shown running on an Acer Aspire Vero prototype on multiple occasions. The prototype was first demonstrated during the 2021 Hong Kong Computer and Communications Festival — a number of photographs from the event detailing various aspects of the user interface as well as version information were posted on BetaArchive by member DiaoSlime in August 2021. The same prototype was then also demonstrated by several tech websites, including UltrabookReview.com and Polish website dobreprogramy.

The posted images demonstrate the new Start menu and taskbar, which appear identical to the ones found in build 21996 and later. The watermark also includes the same notice that advises Microsoft employees not to take screenshots of the build, as seen in build 21990; a build hash is also present at the bottom left corner of the screen. The original poster stated that the user interface in general is very close to other available builds. This build is one out of two known builds to be compiled from a branch with the  prefix, the other being build 21327. The prefix stands for Firesteel, the codename for an internal Microsoft tool related to Windows 11 development.