Windows 10 build 9821

Windows 10 build 9821 is a pre-Technical Preview build of Windows 10. This build was leaked on 11 May 2020. Prior to this build's leak, Polish website WinClub.pl had released one screenshot of it.

It features the search icon on the taskbar and Task View. As with other builds in the fbl_partner_eeap branch, it can also boot with the current date because it is test-signed, not flight-signed, but the system will remind you to install a newer build if you didn't set the date and turn off network adapters to prevent automatic date and time syncing while installing.

Windowed Metro
This build is the first known to be able to run Metro app as a window instead of full screen. The title bars of apps in this environment are colored black.

New icons
Some icons (including Explorer's) have been changed to a flatter style.

Aero changes
DWM-based window animations (particularly when opening and closing windows) have been changed to simpler transitions. In addition, the Aero theme's window borders have been made thinner, though the Aero Lite theme still has the thicker border style.

Branding
This build uses the "Windows Technical Preview" branding on the desktop and "Windows" branding in winver instead of "Windows 8.1" and "Windows 8" in those areas respectively.

explorer.exe error during shutdown
When you shut down, you may get an error with  referring to a null address.

Window thumbnail background color
The background color of window thumbnails on the taskbar retains the default color even if the user changes the theme color. Restarting will fix this bug.

Bug with the Metro
Dragging a window in full-screen mode in Metro apps will result in Metro transitions from Windows 8.1.

Incorrect file operation progress window size
The file operation progress window (which appears while copying, moving, and deleting files) may not extend automatically when more than one operation is in progress.