xprop

Click to select a window and display its properties

$ xprop

$ xprop -root

$ xprop -id [0x200007]

$ xprop -name "[window_name]"

$ xprop -root WM_NAME

$ xprop -spy -id [window_id]

$ xprop -root -set [PROPERTY_NAME] "[value]"

$ xprop -root -remove [PROPERTY_NAME]

xprop [-display display] [-id id] [-name name] [-root] [-frame] [-spy] [property ...]

xprop displays properties of X Window System windows. Properties are arbitrary data that applications and window managers use to communicate, such as window titles (WMNAME), window classes (WMCLASS), and window states.
When invoked without -id, -name, or -root, xprop displays a crosshair cursor allowing interactive window selection by clicking. Specific properties can be listed as arguments to display only those.
Common properties include WMNAME (title), WMCLASS (application class), WMSTATE, NETWMPID, and various Extended Window Manager Hints (NETWM_*).

-display display

Connect to the specified X server.

Query window by numeric ID (decimal or hex with 0x prefix).

Query window by its WM_NAME property (title).

Display properties of the root window (desktop).

Select the window manager frame instead of the client window.

Limit output to the first n bytes per property.

Don't print property types, only names and values.

Monitor for property change events continuously.

Set a property on the window.

Remove a property from the window.

Specify format for interpreting a property.

Print version and exit.

xprop only works with X11 windows; Wayland applications may not expose properties the same way. Window IDs can be obtained from xwininfo or xdotool. Property names are case-sensitive.

xprop is part of the standard X.Org utility collection and has been included with X Window System distributions since the early X11 releases in the 1980s. It remains an essential debugging and scripting tool for X11 environments.

xwininfo(1), xdotool(1), wmctrl(1), xdpyinfo(1)