displaymode is a command-line utility for changing the display resolution on Mac OS X. It will work on Mac OS X 10.6 or later.

To change the resolution of the main display to 1440x900, run the command:

./displaymode t 1440 900

To change the resolution of the secondary display to 1440x900, run the command:

./displaymode t 1440 900 1

You can get a list of active displays and available resolutions by running:

./displaymode d

The output will be a table like:

Display 0:
2560 x 1600 @60.0Hz *
1280 x 800 @60.0Hz
2880 x 1800 @60.0Hz
640 x 480 @60.0Hz !

Display 1:
800 x 600 @75.0Hz *

where each row is the width x height in pixels. * indicates the current mode, and ! indicates modes that are not usable for the desktop.

./displaymode h prints a summary of the options.

./displaymode v prints the version and copyright notice.