Set the primary display on a dual-screen Mac setup

If you are running a dual-display setup, you can easily adjust the primary display monitor in Mac OS X. When would you want to do this? For example, if you have a MacBook Pro 13″ hooked up to a larger external display, and you want the external display with it’s higher resolution to become the primary display, and your MacBook Pro with it’s smaller resolution to become the secondary display.

How to set the primary display on a Mac:

* Have both displays turned on and connected to the Mac
* Open System Preferences
* Click on the Display icon
* Click on the ‘Arrangement’ tab
* Click and hold on the white bar at the top of the current primary display
* Drag the white bar across to the monitor you want to set as the new primary display for your Mac
* Notice the red border that forms around the new primary screen as you drag the white bar into the arrangement, this helps you determine which screen to use
* After you have set the primary display to the screen you wish to use, close System Preferences

Whatever monitor is set as the primary display will become the default display for applications launching, in addition to holding the system menubar, containing all the default desktop icons, and contain the Dock. Using this method you can effectively turn any external display into the main display for any Mac (MacBook, iMac, whatever) which is a really nice way to maximize screen real estate in dual-display setups that feature a smaller screened Mac with a larger external monitor. Note this is different than operating a MacBook or MacBook Pro in clamshell mode, which also will set the external display as the primary.