Set window transparency in Gnome

You could change window opacity/transparency by changing property _NET_WM_WINDOW_OPACITY via xprop command.

Run:

xprop -format _NET_WM_WINDOW_OPACITY 32c -set _NET_WM_WINDOW_OPACITY 0x7FFFFFFF

and then click on window to set it to 50% opacity.

Set opacity via providing window id (obtained from xwininfo):

xprop -id 0x3a00006 -format _NET_WM_WINDOW_OPACITY 32c -set _NET_WM_WINDOW_OPACITY 0x7FFFFFFF

There's another extension called Glassy Gnome that works with newer versions of gnome-shell.

For more details consult the included README.

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