Windows 10 build 9821

Windows 10 build 9821 is a build of Windows 10, which was originally released to Microsoft partners participating in the Ecosystem Engineering Access Program (EEAP), as indicated by the  branch. Polish website WinClub.pl published a screenshot of this build in 2014. The build was later uploaded publicly on 11 May 2020.

It is the first available build to introduce Windows Technical Preview branding.

Branding
This build uses the "Windows Technical Preview" branding on the desktop and "Windows" branding in  instead of "Windows 8.1" and "Windows 8" in those areas respectively. However, on System Properties, the Windows 8 logo has been removed instead and thus, it does not feature any Windows logo.

Taskbar

 * Action Center, a Windows Phone-like notification area, has been added.
 * The Search button has been readded to the taskbar after being absent in Windows 95 build 81.

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

Internet Explorer
F12 Developer Tools may fail to launch.

error during shutdown
When the system shuts down, a memory access error related to  may occur.

Timebomb
Like other builds found in the  branch, this build uses a test-signed certificate and as a result can be installed on the current date. However, installing this build on the current date disables the ability to change the desktop wallpaper in the Control Panel.

Taskbar Language Bar
The language bar is not displayed on the taskbar, but however the old language bar is working properly.

Taskbar preview border color
If window auto-colorization is enabled, the taskbar preview borders do not change color even after the wallpaper changes. This issue can be remedied by manually changing the window color through the Control Panel or by restarting Windows.

File operation window metrics
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.

Closing notifications in the Notification Center
When swiping away all notifications from a system tray application, particularly the Action Center,  will crash.