Problem: Firefox opens in fullscreen mode and will not exit from this mode.
– Close Firefox completely.
– In a command line (terminal), navigate to your firefox profile store directory:
– Locate and change directory (cd) to your profile profile directory (example: cd 12223.username)
– Edit the “xulstore.json” file with your favorite editor (vi or nano):
– Locate this value: sizemode=”fullscreen”
– Change the value “fullscreen” to “normal”
– Save changes and exit (Ctrl+O, Ctrl +X).