Neat trick. Another, similar one, is possible with "xrandr --setmonitor". That doesn't require starting a separate X server & WM instance: https://askubuntu.co

Neat trick. Another, similar one, is possible with "xrandr --setmonitor". That doesn't require starting a separate X server & WM instance: https://askubuntu.com/q/150066#998435 https://askubuntu.com/q/150066#998435 However, both Xephyr/Xnest and "xrandr --setmonitor" create separate non-overlapping screen(s), which means sharing part of a window (say, browser sans chrome [1]) can't be done here, but is possible with OP's tool. [1] EDIT: "chrome", as in - parts of browser's window other than webpage itself: tabs, URL bar, bookmarks, etc...