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I went through a similar question , but the answer was informing how to hide the monitor, but not how to disable it .

I do not want any new windows to creep into the laptop display when the external display is connected. I could not find any in the Display Settings(under System Preferences).

I dont want to close the lid because I think it impacts the air flow of the macbook/pro.

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Reducing heat by adjusting the lid

Having the lid closed or open does not impact the airflow of your MacBook Pro (MBP). Ambient air is never in short supply and the "exhaust" (where the hot air picked up by the blade fan(s) are expelled) is located at the back of the unit (the black stripe on the newer models and the grey stripe on the first generation machines).

Some claim that keeping the lid open allows the chassis to cool down, but these claims have never had any real data behind them (simply anecdotal evidence and unsubstantiated rumour). Personally, I have a 2006 MBP that was eventually relegated to being a desktop. I ran the system for well over a year with the clamshell open, and then closed, and saw no different in CPU/CPU temps (nor any variability in the other heat sensors) as a result. Moreover, the newer models have far more efficient blade fans and would suffer even less from the effects of heat (additionally, the new Intel chipsets run cooler than their predecessors). You can conduct your own testing of course. I had replaced the heat sink, re-applied a sane amount of Arctic Silver thermal paste, and used Lobotomo Fan Control daemon to monitor my system's temperature.

Disabling the internal display, properly

There are two ways to connect a secondary display to your notebook without enabling the default screen (note that this does not mean dimming it, but rather turning it off).

  1. The first is to connect the display with the lid closed when the machine is powered down. Once the external display is connected, turn the machine on—it will detect the secondary display while leaving the internal one turned off. This will alleviate the issues you have with "dragging things off the screen" as the system will constrain your desktop to the one, active monitor.
  2. The second is to connect the secondary display when your system is awake and active, and the clamshell open. Make sure the notebook is plugged in. Once you connect the secondary monitor, the system will recognize it. Once it does, close the lid on your notebook. The device will be put to sleep. Once that happens, move your mouse, or hit a key on your keyboard to wake it. Once it wakens, it will enable the secondary display, but not the internal one.

Additionally, you may set the attribute to leave the system in the sleep state even if the clamshell is opened. You can do this using pmset, a local utility found on OS X that actually handles all your power settings. You can accomplish this with the following command:

sudo pmset -a lidwake 0

The -a, -b, -c, -u flags determine whether the settings apply to battery ( -b ), charger (wall power) ( -c ), UPS ( -u ) or all ( -a ).

To reverse the command, set the 0 to a 1. These settings are persistent, in that, they do not need to be re-applied every time the machine's power is cycled and are saved to the file: /Library/Preferences/SystemConfiguration/

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The command pmset doesn't work on El capitan 10.10.2. Any alternative? – Fred K Dec 16 '15 at 16:01
"Once the external display is connected, turn the machine on" on a Mac laptop, that involves opening the lid/clamshell though. – Adrien Be Feb 8 at 5:45

You could also use a ThirdParty App like


DisableMonitor adds the missing feature to disable a monitor on a Mac. You can also easily disable, enable or change the resolution of a monitor. enter image description here

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Answers on Ask Different need to be more than just a link. It's okay to include a link, but please summarize or excerpt it in the answer. The idea is to make the answer stand alone. – patrix Sep 29 '14 at 13:32
Probably you have not noticed: this is an old thread, my thread is just for completeness, why writing more than necessary? – Eun Sep 29 '14 at 14:05
Answers are more likely to help other users if they explain a bit more about the solution you are proposing. Also please have a look at self promotion in the FAQ. – patrix Sep 29 '14 at 14:31
fwiw, this answer was all that I needed and following the link solved my problem. No further description was required. Up-voted. – Jeremy Baker Jun 7 '15 at 16:50
This application reduces the brightness of the monitor to 0, but it remains on! So probably it consumes more. Is there a way to completely turn off? – Fred K Dec 18 '15 at 10:13

Do as described here:

How can I turn off the screen on the macbook when I have an external monitor set up?

Then open the laptop.

In Snow Leopard this will do what you are asking for. The behaviour may have changed under Lion though. Which OS version are you using?

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I saw the answer, I wanted to see if there is a better way than this. – Sairam Aug 13 '11 at 11:09
Try the keystroke combo Ctrl-Shift-Eject. Does that turn off both monitors or just the internal one? – dan8394 Aug 13 '11 at 11:13
The above combination restores to the previous state – Sairam Aug 13 '11 at 12:23
Sorry Sairam - I don't understand you. State of what? – dan8394 Aug 13 '11 at 12:36
When I try Ctrl-Shift-Eject , it turns off both monitors and internal one . – Sairam Aug 13 '11 at 17:13

You can also make the external display the primary one. By default all new windows will appear on that one. To do this, go to system preferences > Display > geometry, and drag the miniature menu bar to the miniature external display.

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I tried that as well. Some applications I rarely use, tend to open windows on the laptop display. – Sairam Aug 15 '11 at 5:06

My suggestion is to set the displays to 'mirror' then turn the brightness down on your Mac.

Both your screens are the same so you won't lose any windows.

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mirroring wont give me the same resolution. even at 0 brightness, you can see the screen. My problem is that keeping it open blocks a view. hence need to close the lid – Sairam Oct 23 '13 at 3:59
up vote 1 down vote accepted

My question finally answered by running:

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

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Hi if this answered your query please accept the answer :) – macaco Oct 21 '11 at 17:51
It does not seem to work any more. I am using Macbook Pro (Retina, 13', Mid 2014) with 10.10.2. – Lex Li Feb 20 '15 at 4:10

for mac users trying to use hdmi to tv and having troubles turning off your screen on laptop and leaving screen on tv on, TURN THE BRIGHTNESS RIGHT OFF!!!! the laptop screen will go black but tv screen stays the same

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This doesn't prevent windows from begin dragged on to the turned off display. It's nice for saving power and bulb life of course, just not so much an answer to the problem here. – bmike Dec 28 '13 at 20:40
Also the screen doesn't go completely black. In low enough lighting the screen is still visible. – Arc676 Jan 7 at 13:29

When I had my MacBook Pro connected to an external TV, I used the magnet trick.
Placing a small weak magnet (I used one the size of a coin battery) near the bottom of the right speaker would make contact with the Reed Switch, tricking the MBP into sleep mode, with the lid open, while using the external display only.

While this worked fine for the time I had the external TV and I never read any reports about this technique damaging anything (there ARE magnets inside the MBPs), I would try a software based solution, first.

Some references:

iBook and PowerBook Clamshell Sleep Control
Location of magnet and Reed Switch for various Mac laptop models and instructions on how to use both a magnet to force sleep with the lid open or a thin piece of iron alloy to prevent sleep with the lid closed.

Reed Switches
Location of magnet and Reed Switch for the MacBook Pro 15" with pictures.

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