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I have a Mac mini in a somewhat complex home-theatre setup. Often the Mac won't correctly recognize the TV as a display. The TV will just report "No signal". There are two methods to recover from this state.

  1. Unplug the display cable from the Mac and plug it back in
  2. Sleep the Mac and wake it up again.

Both are a bit cumbersome. Is there any way to force the Mac to re-detect or re-initialize it's displays? I've tried Command-F2 and a couple AppleScripts but nothing seemed to work.

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5 Answers 5

Reset to default
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This is really old but I found a solution that still works in OS X 10.11.2:

hit cmd + "brightness up" for display detection and cmd + "brightness down" to switch between mirror and extend display modes. It seems to be the brightness keys and not necessarily the F1 and F2 key.

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21

Just press the option key while you're in Displays in System Preferences. You'll get a Detect displays button (bottom right).

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  • 2
    Great -- option key does the magic. Wonder why they hide it!?
    – DustinB
    Apr 8, 2013 at 19:09
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    Unfortunately even this doesn't seem to always work. It still splits over two displays :(
    – Nicholas Tolley Cottrell
    Aug 8, 2013 at 18:42
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    Good tip, but it's hard to press a button when you can't see the display :)
    – amrox
    Mar 15, 2016 at 19:53
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    Nope the button does not work.
    – Sephethus
    Nov 25, 2016 at 23:45
  • doesn't work on new macs
    – Nahum
    Jan 11, 2022 at 7:38
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Here is an AppleScript someone wrote for 10.4 which may help you:

http://www.insanelymac.com/forum/index.php?s=&showtopic=59163&view=findpost&p=457644

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2

In the displays prefplane, there is a checkbox "Show displays in menu bar". If you check it, you get this somewhat strange new icon in the menu bar that has "Detect Displays" as its first option.

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1

In the displays prefpane there is a button 'detect displays' (But I'm on a MacBook, not a mini with a TV.)

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  • The problem is that I can't see the screen to click the button in the prefpane. I've tried scripting it and binding it to a hotkey but had no success.
    – amrox
    Feb 26, 2010 at 15:03
  • Ah... I've been using with secondary monitor - the laptop has it's primary built in. Are you able to plug in a working monitor and get the cursor and/or keyboard focus in position?
    – Justin Love
    Feb 26, 2010 at 15:45

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