Windows 11 build 21380

Windows 11 build 21380 is an early build of Windows 11 which was shown running on an Acer machine during the 2021 Hong Kong Computer and Communications Festival. A photo of the watermark and  was posted on BetaArchive on 21 August 2021 by member DiaoSlime. The watermark includes the same notice that warns users not to take screenshots of the build, as seen in build 21990.

The original photographs only show the right taskbar corner and the contents of the  dialog, although the original poster stated that the user interface is very close to build 21996 and later Windows 11 builds.