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I’m using my MacBook Pro (OS X 10.6) standing in a shelf with an external screen on my desk so I don’t use and need the internal screen. But if the internal one is on it’s shown in spaces.

It is possible to use the MacBook with the internal screen switched off by putting it to sleep and wake it with an external input device while the Book is close. But this way always needs a short sleep and interrupt working. So I wonder if it’s is possible to switch off only the internal screen by software (an app, via Terminal, AppleScript, a keyboard short cut etc.) without switch off the external screen?

I know that there’s a shortcut for “sleep screen“ but this affects all screens including the external one.

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7 Answers 7

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If it wasn't clear from the comments, the behavior of clamshell mode changed in 10.7:

  • If a laptop is connected to an external display, closing the lid doesn't put the laptop to sleep.
  • If you open the lid after that, the internal display is turned back on.

sudo nvram boot-args=iog=0x0 restores the behavior in 10.6 and earlier.

If others were looking for a way to trigger normal display sleep (like when pressing ⌃⇧⏏), you can use SleepDisplay.

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  • Thanks. In the meantime I dated up to ML and discovered the new behaviour.
    – Tobi
    Oct 3, 2012 at 19:08
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+50

To disable the internal screen for OS X Lion based laptops, launch the Terminal and enter the following command:

sudo nvram boot-args="iog=0x0"

You’ll need to reboot for changes to take effect, and the internal display will then be completely disabled regardless of whether the Mac is open or closed.

To undo this, you can go back to the Terminal and enter:

sudo nvram -d boot-args

Then reboot again, or you can just zap PRAM by holding down Command+Option+P+R during reboot, which clears out the boot-args as well. If you were to disconnect the MacBook Pro from an external video source, zapping the PRAM would be how you’d want to reenable the internal display.

This is the opposite of “clamshell mode” – where the Mac laptop is closed and the screen is still turned on. Clamshell can look nice, but without adequate air flow the Mac may overheat, thus running the computer with the display open is recommended. If you’re going to do this, be sure to set the primary display so that the menubar, Dock, and alert windows go to the proper screen.

Source: OSXDaily

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  • Thanks. But unfortunatly I’m running the Snow Leopard. Furthermore the rebooting is more effort than using the clamshell mode. Plus: In clamshell my internal display is off but after waking the MacBook I can open it while the screen stays off.
    – Tobi
    Apr 18, 2012 at 8:41
  • This seems like a dangerous and terrible idea. Am I missing something? I am well aware that you just zap the PRAM.
    – Jason Salaz
    Apr 24, 2012 at 7:23
  • What exactly is this doing? Does anyone know what exactly happens when you do this, or if there's a better option out there? I've seen this all over the net, but no answer to the "how it works" question.
    – Aaron Ash
    Jun 25, 2012 at 16:12
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If I understand it correctly, you want to only be using your external display and have the internal display to be shut off. To achieve this, you want to put your macbook in clamshell mode.

To do this you must have your macbook attached to
        a) an external power source
        b) an external display
        c) external keyboard + mouse.
Then all you do is close the lid (see pic below).

When you want to put your mac to sleep you press opt+cmd+eject, and when you want to turn it on again you press any key on your wireless keyboard, having your macbook closed at all times.

More info can be found here.

MBP in clamshell mode

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  • Thats exactly what I do at the moment and what I said in the comments above ;-) I wont a solution that doesn’t need the short sleeping to switch the display off.
    – Tobi
    Apr 21, 2012 at 17:44
  • I'm not sure what you mean then. You don't have to "put your macbook to sleep first" like you say in the comments to enter clamshell mode. Can you explain what you mean?
    – Milo Wielondek
    Apr 21, 2012 at 17:51
  • I just like to switch off only the internal display and us the Mac as like it is in clamshellmode, but I want to prevent the step of sleeping and wake the Mac. So the result is the same as with your way but without the detour of sleeping.
    – Tobi
    Apr 21, 2012 at 18:00
  • You do not have to put your mac to sleep in order to use clamshell mode. Maybe you're doing something wrong? Can you explain what you mean by sleeping your mac? Do you want to have the lid open, is that it?
    – Milo Wielondek
    Apr 21, 2012 at 18:02
  • @Tobi If you're talking about the short delay that occurs when you close the lid, then the only solution that comes to mind is to dim your screen using the F1-key on your keyboard. That way your internal screen will appear off, but it will however still be present in spaces (although it won't show on the second monitor). I'm afraid there's no other way around that than using the clasmshell mode. You'll either have to live with the delay or accept that your internal screen must stay on.
    – Milo Wielondek
    Apr 21, 2012 at 18:40
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A solution for clamshell mode that works using Monterey without Third Party tools:

  1. run sudo nvram boot-args="niog=1" in Terminal
  2. reboot with the External Display connected
  3. close the lid
  4. use a plastic card (or similar which can't cause harm to your screen) to hit any key with the lid very slightly opened so that the internal display is not triggered
  5. continue to open the lid

This behaviour gets reset as soon as your Mac goes to sleep, so use a tool like Amphetamine (or native pmset in Terminal) to keep your computer awake. If your Mac went to sleep with the lip opened, it may be that closing it and waiting of a couple of seconds will turn the external display on. After opening then, clamshell mode persists.

Update It seems to be the case that MacOS has a detailed protocol of determining when allowing lid-open clamshell mode. If you have an external input device available, follow these steps:

  1. Run sudo nvram boot-args="niog=1"
  2. Run sudo pmset -a lidwake 0
  3. Reboot
  4. Unplug the external monitor
  5. Close the lid
  6. Plug in the monitor
  7. Trigger your external input device (or plastic card)
  8. Reopen the lid

Lid-open clamshell mode should now have been invoked.

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You know, you could just put the laptop into display mirror mode instead.... Just turn the brightness all the way off on the laptop display.

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  • 1
    Thats no option for me because the external monitor needs more pixels than the internal one …
    – Tobi
    Apr 23, 2012 at 8:41
  • @Tobi, oh well then, you'll just have to upgrade to Lion. What you are asking for cannot be done under Snow Leopard.
    – Old Pro
    Apr 23, 2012 at 10:34
  • What do you mean? What can Lion do in this case that SL can’t?
    – Tobi
    Apr 23, 2012 at 14:16
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    @Tobi, in Lion if you have an external display plugged into the laptop and the laptop is plugged into a power source, when you close the laptop lid the internal display is turned off without putting the laptop to sleep. Just like you want.
    – Old Pro
    Apr 23, 2012 at 16:39
  • Thanks. What happens if I reopen the lid (cause that’ll be better for cooling the Book)?
    – Tobi
    Apr 27, 2012 at 16:00
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While I haven't been able to find a command that will sleep the display natively, there is an app you download that will do it. There are two options from here.

  1. Install the app to the Applications folder and from Terminal or SSH run open /Applications/Sleep\ Display.app

  2. Right click on the app from the Downloads folder and click "Show Package Contents". Navigate to Contents/MacOS and copy the sleepdisplay file.

    Navigate to /usr/bin (you can use the ⇧+⌘+G shortcut and type the directory in) and paste the binary file. You will now be able to type the command sleepdisplay into Terminal or through SSH and the display will immediately go to sleep.

Hope this helps!

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    Thank you but this software affects all screens not only the internal one. It does the same as ctrl + shift + eject.
    – Tobi
    Mar 30, 2012 at 12:56
  • Just so you know, even if you find away to selectively put displays to sleep so that the built in display is asleep and the external display is not, it will still show up in Spaces as a useable desktop. If you really want to use your MacBook Pro's hardware with an external display and not use the built in display, I would suggest clamshell mode.
    – Matt Love
    Mar 30, 2012 at 13:53
  • The clamshell mode is what I use at the moment but I would like to switch off the internal display (as clamshell does) without putting the MacBook to sleep first.
    – Tobi
    Mar 30, 2012 at 13:57
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I wanted to do similar thing and this is what I found. Clamshell is the answer but an overlooked step of clicking a mouse button to switch on the external display worked. I found this at: http://osxdaily.com/2012/06/08/quickly-enter-clamshell-mode-with-an-external-display-in-mac-os-x/

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  • This does not answer the OP's question as your solution also works by first sleeping and then waking the Mac.
    – gentmatt
    Oct 30, 2012 at 11:04

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