xkill
Forcefully terminate a graphical program (X client)
TLDR
Display a cursor to kill a window when pressing the left mouse button (press any other mouse button to cancel)
Display a cursor to select a window to kill by pressing any mouse button
Kill a window with a specific ID (use xwininfo to get info about windows)
SYNOPSIS
xkill [-display displayname] [-id resource] [-event event-number] [-button button-number]
PARAMETERS
-display displayname
Connects to the specified X display instead of $DISPLAY.
-id resource
Kills the client with the exact window resource ID (hex or decimal).
-event event-number
Listens for custom X event (default: ButtonPress, event 4).
-button button-number
Triggers on specified mouse button (default: 1).
DESCRIPTION
xkill is a powerful X Window System utility designed to forcibly terminate misbehaving or frozen client applications. Upon invocation without options, the cursor transforms into a skull-and-crossbones icon, signaling that clicking on any window will send a KillClient request to the X server, abruptly ending the selected client regardless of its state.
This tool shines in scenarios where graphical apps hang, ignoring close buttons or keyboard shortcuts. It's a quick recovery method in X11-based desktops like those using Openbox, i3, or even GNOME/KDE under Xorg.
However, precision is crucial: accidental clicks can destroy your window manager, panel, terminal, or compositor, potentially stranding you in a bare X session. Always prepare a virtual console (e.g., Ctrl+Alt+F3) beforehand.
Advanced modes allow non-interactive use via resource IDs (obtained from xwininfo) or custom mouse events/buttons, enabling scripted automation or remote debugging. Despite its age, xkill remains indispensable for X11 users facing uncooperative windows.
CAVEATS
Dangerous tool: Can kill window manager, shell, or desktop. Test in VM first. Cancel interactive mode with Delete or Esc. Use -id for safety. Ineffective on Wayland.
INTERACTIVE CANCEL
In cursor mode, hit Delete or Esc to abort without killing.
GET WINDOW ID
Run xwininfo -tree -root or xprop | grep -i '^_net_wm_name' then select for ID.
HISTORY
Developed by the MIT X Consortium; debuted in X11 Release 4 (1989) as a core debugging aid. Maintained in xorg-x11-apps; unchanged core functionality across decades.
