When the swapped data is needed, it is fetched back. In the event that the available video memory is not enough to store all the video data and textures, the currently unused data is moved out to the system RAM or to the drive. The WDDM driver allows virtualization of video memory, and the video data is split from the video memory into the system RAM. In a graphical context, virtualization means that individual processes (in user mode) cannot see the memory of adjacent processes even by inserting rogue commands in the command line. The WDDM driver provides new areas of functionality, not available in previous display driver models.

WDDM requires at least a video card that supports Direct3D 9c and the display driver to implement device driver interfaces for the Direct3D 9Ex runtime to run legacy Direct3D applications it can optionally implement runtime interfaces for Direct3D 10 and later. It also supports the new DXGI interfaces needed for basic device creation and management. WDDM provides the functionality needed to render desktops and applications using Desktop Window Manager, a composite window manager that runs on top of Direct3D. However, with the removal of XDDM from Windows 8, WDDM has become the only option. The display driver in Windows Vista and Windows 7 may be WDDM or XDDM compliant.

WDDM is a replacement for the previous Windows 2000 and Windows XP display driver model, XDDM/XPDM, which aims to support better graphics performance, new graphics functionality and stability.

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