Window mode

Windows

To change the game from running full screen to running in a window, in the settings.txt file change

fullscreen=yes

to

fullscreen=no

The window size is given by.

  size=
  {
     x=1280
     y=960
  }

EU3 allows freely defined window sizes, so you might want to modify it slightly in order to see f.x. the menu bar

  size=
  {
     x=1270
     y=930
  }

Windows users can also take advantage of the Gamers Window Relocator located at http://gwr.orekaria.com/; giving the user a windowed-borderless effect.

Mac

The Mac game automatically starts in windowed mode. You can go fullscreen by using Command+F.