Force q uit

If an app stops working and won’t quit the normal way, or starts to open but stalls, hold down Opt after Ctrl–clicking its icon in the Dock and choose Force Quit. Alternatively, press Opt+Cmd+Esc to open the Force Quit Applications window, then choose which app to close. Use this as a last resort, as any work in the app not saved will be lost. Other apps are unaffected, and there’s usually no need to restart.