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

Unlike the Mac OS (Apple Macintosh) and Microsoft Windows platforms, 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:

customizability of appearance and functionality:

textual menus used to start programs and/or change options

docks and other graphical ways to start programs

multiple desktops and virtual desktops (desktops larger than the physical monitor size), and pagers to switch between them

consumption of memory and other system resources

degree of integration with a desktop environment, which provides a more complete interface to the operating system, and provides a range of integrated utilities and applications.

How X window managers work

When a window manager is running, some kinds of interaction between the X server and its clients 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 typically 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 instead of 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 accountable for icons. Indeed, icons do not exist at the X Window System core protocol 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. Some window managers do not support icons.

While the main aim of a window manager is to manage the windows, many window managers have extra 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.

Specialised types of window managers

Several dedicated types of window manager exist.

Virtual window managers

A virtual window manager is a window manager that uses virtual screens, whose resolution can be higher than the resolution of one's monitor/display adaptor. This environment is very useful when one wishes to have a large number of windows open at the same time. A number of virtual window managers have been made, including FVWM, Tvtwm, HaZe and others.

Tiling window managers

A tiling window manager is a window manager with an organization of the screen into mutually non-overlapping frames (hence the name tiling), as opposed to the traditional approach of coordinate-based stacking of objects (windows) that tries to emulate the desk paradigm. The following is a list of tiling window managers.

Larswm

Ion

TrsWM

Stumpwm

wmii

dwm

ratpoison

XWEM

Xmonad

awesome

Popular X window managers

AfterStep

Blackbox (minimalist)

evilwm

Enlightenment

Fluxbox (lightweight, based on Blackbox)

FVWM (a virtual window manager, derived from twm)

IceWM

Ion (a tiling tabbed window manager designed with keyboard users in mind)

KWin (originally called KWM, default for KDE)

Metacity (the current default for the GNOME desktop environment)

MWM (Motif Window Manager), Motif Window Manager

Sawfish (a past default for GNOME, originally called Sawmill)

twm (default for the X Window System since version X11R4)

Window Maker

Xfwm4 (a window manager for the Xfce desktop environment)

Compositing window managers

Beryl

Compiz

Metacity (default for GNOME since version 2.2)

Xfwm (default for Xfce)

Other X window managers

4Dwm

5Dwm (derived from mwm, true SGI look&feel)

9wm (clone of the original windowing system of Plan 9)

aewm

amiwm Amiga workbench unix clone.

CTWM

cwm

EvilPoison (a fork of evilwm with Ratpoison-like keybindings)

FVWM95

hackedbox

HaZe

JWM (Joe's Window Manager)

Kahakai

Luminocity (experimentation in compositing)

LWM

Matchbox

olwm (and olvwm with virtual desktops, OPEN LOOK window managers)

Openbox

Orion A nested (tiled or floating) window manager written in Scheme and scsh

Oroborus

PekWM

PLWM

PWM

Qvwm (Windows 95/98 look-alike) (list of forks)

Ratpoison

Scwm (the Scheme constraints window manager)

SithWM evilwm-based, virtual window manager(german page)

swm (the original virtual desktop implementation)

Toy'd (HomePage GoogleProject a portable window manager for MS-Windows & UNIX / Linux platforms)

TrsWM

uwm

vtwm

Waimea

WindowLab

wm2

WMI

XPwm (for XPde, Windows XP Look alike) - now defunct

xwm