How to Change the Screen Resolution on a 27" iMac

by Andrew Tennyson
Kevork Djansezian/Getty Images News/Getty Images

Your iMac features a high-definition screen that you can set to several different resolutions using the computer's System Preferences panel. Changing the resolution may prevent some applications from fitting entirely on your screen and can therefore limit your access to menus and other on-screen functionality.

Step 1

Click the "Apple" menu in the upper-left corner of your screen and select "System Preferences" to load your iMac's System Preferences panel. The Apple menu is identified by a small Apple logo. System Preferences is the location on your Mac where you customize computer settings.

Step 2

Click the "Displays" icon to load the Displays settings panel. The Displays icon resembles a computer screen and is located in the second group down on the System Preferences panel.

Step 3

Click the "Display" tab if it is not already selected and then click the "Scaled" radio button. If you have never changed your display settings in the past, your iMac will have "Best for display" selected by default, but you need to select Scaled to change the resolution from the native resolution.

Select the resolution you want to use from the list of available resolutions and then wait for the iMac to reset the display. It should take no longer than 15 seconds for the iMac to automatically recalibrate itself.


  • Information in this article applies to 27-inch iMac computers running the OS X Mavericks operating system. Procedures may vary with other versions or products.


  • If the display does not recalibrate itself automatically after you select a new resolution, press the "Esc" key to return to your previous resolution.
  • If the screen remains unresponsive after pressing the "Esc" key, press "Control-Command-Eject" to restart the iMac.
  • If the display still persists in not changing its resolution automatically, you can change it manually in Safe Mode. To perform this operation, hold down the iMac's "Power" button to turn it off. Press the "Power" button again to turn the computer on, and then immediately press and hold down the "Shift" key as soon as you hear the OS X startup tone. Release the "Shift" key when the progress indicator appears below the Apple logo. Click the "Apple" menu in the upper-left corner, click "System Preferences," click "Displays" and then click the "Display" tab. Select a new resolution for your screen and then restart the iMac.
  • If you've connected a second display to your iMac, you can adjust its resolution in the same way. Press the "Option" key when you click the "Scaled" radio button in the Displays settings panel to see a list of available resolutions for your second display.


Photo Credits

  • Kevork Djansezian/Getty Images News/Getty Images

About the Author

Andrew Tennyson has been writing about culture, technology, health and a variety of other subjects since 2003. He has been published in The Gazette, DTR and ZCom. He holds a Bachelor of Arts in history and a Master of Fine Arts in writing.

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