Which compositing window manager has been in Microsoft Windows since Vista?

The compositing window manager in Microsoft Windows since Vista is the Desktop Window Manager.

Usually abbreviated DWM, the Desktop Window Manager creates the final desktop image by composing individual application-window surfaces. Instead of every program drawing directly into one shared display buffer, applications render into off-screen buffers that DWM combines before sending the result to the screen.

DWM was developed to support the Windows Aero experience introduced with Windows Vista. Its composition model enabled effects such as translucent window borders, live taskbar thumbnails, animated window switching, and smoother movement with reduced flicker. It uses Microsoft’s graphics stack, including Direct3D and hardware acceleration when compatible drivers are available.

The name is sometimes confused with Quartz Compositor, which belongs to macOS, or Compiz, a Linux desktop compositing project. DWM is a Windows component, not the same thing as the desktop shell or File Explorer. It also appears in Windows Server 2008 when the Desktop Experience feature and suitable graphics drivers are installed. From Windows 8 onward, DWM became continuously required for the desktop experience.