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My Macbook Air stopped detecting the resolution of my external display this morning and I'm not sure why because it was working fine last night. My display is 24" 1080p and in the past whenever I have connected my monitor to my Macbook, it's just used the 'Best for Display' resolution. Today though, this automatically defaults to 800x600 and looks like the picture on the left. Then when I change the resolution to 1920x1080 it looks like the picture on the right (click to enlarge).

Things that I've tried so far:

  • Rebooting the MacBook
  • Disconnecting and reconnecting the Mini DisplayPort
  • I've tried with another computer (Windows) and it displays fine.
  • Resetting the settings of the monitor and doing and auto adjustment.

The fact that it's limited to this computer means that it's not the monitor, I'm wondering if there is any way to reset the display/graphics controller or something? Thanks.

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3 Answers 3

Reset to default
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With the Display pane of System Preferences visible, hold down the Option key and the "Gather Windows" button in the lower right should turn into a "Detect Displays" button. Click on that button and your computer should take care of the rest.

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I suspect this is a duplicate of my-macbooks-external-monitor-is-magnified, but I'll put my answer from that here:

I just had this problem on High Sierra 10.13.4 on my 2015 Retina Macbook. Solution was to reset the SMC (as per idownloadblog):

  1. Power off computer
  2. Press and hold altogether left Shift Ctrl Alt and the power button for a couple of seconds.
  3. Wait nervously for what feels like ages.
  4. Press the power button. Probably nothing happens.
  5. Wait even longer and avoid biting fingernails
  6. Press the power button.
  7. Hear startup chime with great relief.
  8. When computer comes back up the display may still be zoomed, but if you go to the display preferences you should now be able to find a resolution that works (previously, for me, the correct display resolution was not available for the external display).
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  • Just a straight up reboot fixed it for me - very strange. For context, I had a display that was intermittently rendering the right resolution. I thought it was an issue with the cables and changed those around but it didn't really help. No amount of alt clicking the detect display button did anything either.
    – Tejaswi Yerukalapudi
    Sep 1, 2021 at 15:50
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On my MacBook Pro with OS X 10.8.3 I have a configuration file for each external display I connected to my Mac in this folder: /Library/ColorSync/Profiles/Displays. If you can identify the file for your display from that list, try moving the file to a different folder and reconnecting your monitor. This solved an issue I was having with colours not showing correctly.

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  • ColorSync profiles are for color profiling, hence the name. It has nothing to do with the resolution.
    – bot47
    May 31, 2014 at 11:30

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