How to Detect Displays on a Mac with OS X El Capitan, Yosemite, Mavericks

Mar 31, 2014 - 30 Comments

Detect Displays in Mac OS X

Typically when an external display is connected to a Mac, it will automatically be detected and start working instantly, with the Mac either extending the desktop or mirroring the screen over to the newly attached display output. Sometimes that doesn’t happen however, and when a secondary screen is not detected automatically by the Mac, you’ll want to trigger the “Detect Display” function in OS X.

Like some other features in new versions of OS X, the “Detect Displays” button is now hidden by default, no longer immediately visible in the Display Preferences of OS X El Capitan, OS X Yosemite, and OS X Mavericks. This does not indicate a problem with the Mac or with the external screen you wish to use, you simply have to toggle the Option key to make the detect feature visible and then be able to run the detection as usual. This applies to secondary displays of all types, whether it’s an external monitor, AirPlay mirroring, AirDisplay, a projector, an HDMI connection to a TV, or whatever other additional screen you have attempted to connect to the Mac. If you’re having any issues either showing the feature or getting an external screen to show up properly, this is what you’ll want to do.

Use Detect Displays for External Screens on a Mac in OS X

With the secondary display to detect already connected to the Mac, do the following:

  1. Go to the  Apple menu and choose System Preferences
  2. Choose the “Displays” panel
  3. Hold down the “Option” key to show the “Detect Displays” button – note that it replaces the ‘Gather Windows’ button
  4. Click on “Detect Displays” while holding down Option to use the function as intended

Show Detect Displays in Mac Displays panel

At this point the external screen should be found and work as usual, launching the secondary “Displays” window for that screen. Of course you’ll want to be sure the physical connection is secured for the external display, and if you’re having any issues check the cables to the LCD monitor, projector, or TV.

It should be pointed out that having the “Detect Displays” button not being visible in OS X Mavericks is not an indicator of a problem or a bug, and it’s certainly not indicative of an issue with the output device, it’s simply hidden from casual use, presumably because most of the time the Mac usually has no issues finding and connecting to external screens. Nonetheless, sometimes you have to forcibly detect an external display, which is why this feature is a little curious to hide by default.

Using the “detect” feature should be the first troubleshooting step taken if you can’t find a video output device that is connected to a Mac, though more advanced methods may need to be taken if there are other issues, such as flickering or noisy displays, which may require an SMC reset to resolve.

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Posted by: Paul Horowitz in Mac OS X, Tips & Tricks


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  1. R Tucker says:

    Is there a way to make the [detect displays] button show by default? I use this quite a bit connecting to various displays for presentations.
    Thanks. RT

  2. LensKaraoke says:

    I do this all the time in my job but with the new Mavericks I get the menu bar across the top on the external screen. Is there a way to get rid of this

  3. CD says:

    This is such a good tip. Before I read this tip, I would have to restart my MacBook in order to get it to detect my external monitor. Thank you!

  4. Michael says:

    Is this another ‘improvement’ by the iOS team? Yes, the mac should detect the display (or projector) automatically, but it usually doesn’t if the device was made by Dell.

  5. L_MO says:

    Using the option button does display the hidden display button but nothing happens when I click it. Macbook still does not connect to Sony Bravia. Any other suggestions?

    • D_Po says:

      Same…Any help?

      • andrea says:

        the same here!

        • Sim says:

          Me too, tried restarting and clicking for ages.

          • Anthony says:

            Same here… realllllly need it for work.

          • larryy says:

            Ditto, connecting to Denon receiver then to Sony projector. Everything worked great until I installed El Capitan. Now most times (though curiously not all) when I turn the Denon & Sony off and then back on, the Mac no longer knows anything about the home theater system. The only audio output listed is internal speakers or Airplay. Clicking Detect Display does nothing. I’m having to reboot my Mac Pro every day now. It’s a major pain. I can tell everything is fine on the Mac, aside form its HDMI sync, because I can use Screen Sharing to connect to it and display its current state. But I have to either use Screen Sharing and reboot from the Apple menu or ssh in and reboot from the command line to have the Mac see the Denon/Sony display. If anyone has any hints about fixing or working around this they would be much appreciated.

  6. LO says:

    I’ve had trouble with this for years. Genius tip – thank you!!!!!!!

  7. scott says:

    this option didn’t work for me. When I help down the option key, nothing changed??

  8. Robin says:

    An update for yosemite would be great as this fix is not applicable on the newest version

    • Paul says:

      This works 100% the same in OS X El Capitan and OS X Yosemite, hold Option and the button will change to Detect Displays. Using Yosemite and El Capitan right now with external screens, use this frequently.

  9. June says:

    It didn’t work. I followed your direction and could click Detect Displays button. but nothing happened. :-(

    • Terry says:

      Odd that the detect display is hidden. Why would Mac do this? Why? That is the question. Steve Jobs would not approve. His point was to make things easy. This reminds me of the days of cntrl alt delete on PCs! Possibly computer scientists have finally gone off the deep end of the digital world since Jobs is not there now to slap them back into reality.

  10. Richard P says:

    Same problem here. Using a Dell P2310H that worked flawlessly until this morning when I put Al Capitan or whatever its called on it. Now it may as well be a dead monitor. Pretty frustrated about this, I need this landscape monitor for Eclipse – coding on a Macbook Pro even if the screen is pretty big is still a bit cramped.

  11. David says:

    This is great info as I had one display which would not detect all the time but this made it work.

    REALLY retarded you have to hold down the option key for to have a button to do this show up.

    WTF???? Is all I can say.


  12. sNuFßøx says:

    Cannot get this to work either. Tried restart but no dice. Anyone have any other fixes?

  13. JMHO says:

    What an inane and arbitrary change. Thanks for the help though, I could not figure this out.

  14. Bruce Baldwin says:

    This “fix” obviously doesn’t work for lots of people, including me on my brand new mac book pro. Occasionally I can make the 2nd monitor work by unplugging cable from monitor at the mac and plugging it into the other thunderbolt port. (Using Apple’s VGA to Thunderbolt converter). Otherwise, 5 to 10 minutes later, the second monitor wakes up. Talk about speedy processors…

  15. ted b says:

    same problem here. macbook air circa 2011 with a new monitor. bought the thunderbolt to HDMI cable, and NADA! Tried the detect displays button, but no dice. no signal as yet.

  16. ness h says:

    Has anyone figured this out yet? I updated to El Capitan and can’t get the displays working. Option key will allow me to see the detect displays but nothing after that?
    I need this to work for my class! Everything was all easy before upgrading!

    • kevin meyer says:

      hi ,
      same problem here did you found a way to fix it ???
      i was about to update to el captain but it seams not to be a solution …
      very frustrating grrrrrr !!!!
      thanks for your reply
      kevin .

  17. Emma Dresser says:

    Hi there
    Still trying to connect my second screen which was working fine up until Christmas. The ‘detect display’ button appears but nothing happens. Have restarted, updated etc. but still doesn’t work. Incredibly frustrating.
    Thanks for your help so far!

  18. Aguinas says:

    Tried like 10 different brands of Thunderbolt/mini displayport cable to HDMI on my macbook air 2011 but none works. :(

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