X window manager

An X window manager is a window manager which runs on top of the X Window System, a windowing system mainly used on Unix-like systems.

Unlike the classic Mac OS, macOS (Apple Macintosh) and Microsoft Windows platforms (excepting Microsoft Windows explorer.exe shell replacements) which have historically provided a vendor-controlled, fixed set of ways to control how windows and panes display on a screen, and how the user may interact with them, window management for the X Window System was deliberately kept separate from the software providing the graphical display. The user can choose between various third-party window managers, which differ from one another in several ways, including:

When a window manager is running, some kinds of interaction between the and its are redirected through the window manager. In particular, whenever an attempt to show a new window is made, this request is redirected to the window manager, which decides the initial position of the window. Additionally, most modern window managers are reparenting, which usually leads to a banner being placed at the top of the window and a decorative frame being drawn around the window. These two elements are controlled by the window manager rather than the program. Therefore, when the user clicks or drags these elements, it is the window manager that takes the appropriate actions (such as moving or resizing the window).

Window managers are also responsible for icons. Indeed, icons do not exist at the level. When the user requests a window to be iconified, the window manager unmaps it (makes it non-visible) and takes the appropriate actions to show an icon in its place. Most modern window managers do not literally show icons to represent iconified windows anymore. Often, an auxiliary toolbar program will allow access to iconified windows.

While the main aim of a window manager is to manage the windows, many window managers have additional features such as handling mouse clicks in the root window, presenting panes and other visual elements, handling some keystrokes (e.g., Alt-F4 may close a window), deciding which application to run at start-up, etc.

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