On startup, the system tray must acquire a manager selection called _NET_SYSTEM_TRAY_Sn, replacing n with the screen number the tray wants to use. The conventions for manager selections are defined in the ICCCM.

Because the selection owner window should be destroyed when the manager selection is lost, normally the selection owner window will not be the same as any of the user-visible windows provided by the system tray.

A system tray that fails to get the selection or loses the selection should assume that another system tray is running, and let the selection owner handle tray icons.

An application wishing to provide an icon to the system tray should first locate the system tray by requesting the owner window of the manager selection. If the manager selection has no owner, clients may use the method described in the ICCCM (watching for a MANAGER client message) to be notified when a system tray appears.