Desktop Window Manager

The Desktop Window Manager is the desktop compositor responsible for providing the Windows Aero visual style and effects, such as live thumbnails in the taskbar. It replaced the Desktop Composition Engine starting with build 4066 of Windows "Longhorn".

Windows Vista
In versions of Windows prior to Windows Vista, applications painted their visible region directly to the surface displayed by the video card, which often resulted in various visual artifacts, such as window trailing. Under the Desktop Window Manager, windows are drawn to off-screen surfaces in video memory. Due to being rendered off-screen, these representations can be used for various visual effects, such as Flip 3D.

Windows 7
The DWM saw significant performance improvements in Windows 7. New features were also added, including:


 * Aero Peek: previews the desktop by making all open windows transparent. When hovered over, taskbar thumbnails display full window previews.
 * Aero Snap: allows most windows to be snapped to either side of the screen or maximized by dragging the window towards the top. Although it is branded with the Aero moniker, this feature is available if the Desktop Window Manager is disabled.
 * Aero Shake: the ability to minimize or restore inactive windows by shaking the active window.

Windows 8
The Desktop Window Manager in Windows 8 is capable of software rendering if the machine does not have capable hardware. New features include support for stereoscopic 3D, composition of the Start screen, and management/separation of desktop applications from Windows Store applications. The Desktop Window Manager cannot be disabled.

In build 7989, the DWM crashes while changing visual styles.