EWMH

The Extended Window Manager Hints (EWMH) is a specification for the X Window System that standardizes how client applications and window managers communicate. Developed under the freedesktop.org umbrella, EWMH extends the older ICCCM 2.0 conventions to provide a more consistent and interoperable set of window management features. It is also commonly referred to as NETWM hints.

EWMH defines a set of root window properties (atoms) and conventions that allow both clients and window managers to exchange information about windows, desktops, and behaviors. Clients advertise their capabilities and states by setting properties on their top-level windows, while the window manager reads those properties to manage windows appropriately. The mechanism relies on the X11 atom system and is designed to work across different window managers and desktop environments.

Key concepts in EWMH include window types, window states, and desktop assignment. Window types categorize windows as desktop, dock, toolbar, menu, utility, splash, dialog, or normal, guiding how they should be treated by the window manager. Window states describe attributes such as fullscreen, maximized (horizontal and vertical), sticky, skip_taskbar, and skip_pager. The _NET_WM_DESKTOP property associates a window with a particular desktop or workspace, enabling multi-desktop setups. Titles and names are exposed via _NET_WM_NAME and related properties, with icons and other presentation hints also standardized.

EWMH enjoys broad support among major X11 window managers and desktop environments, such as Openbox, KWin, Mutter, i3, and Xfwm. It remains the de facto standard for inter-client and inter-window-manager communication on X11, and is often honored by XWayland components to ensure compatibility with Wayland-based environments. See also ICCCM and freedesktop.org specifications.