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I have a plasma TV attached to my Mac Pro. I use it maybe once a week, to watch movies. Rest of the time it just stays connected to my Mac. The problem is that Spaces in bird eye’s view always displays a box for the plasma, which makes my main display’s box too small.

Is there a way to disable the secondary display without actually unplugging it?

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8 Answers 8

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12

Sorry this happens to be a year later, but I was just looking for a way to disable my secondary display and came across SwitchResX. It has a taskbar menu item to quickly disable any connected monitors.

I'm not sure if this will solve your Spaces issue, but it might be worth a try.

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  • Ooops. I have found this SwitchResX some time ago and already have forgotten about my question here on SuperUser. Thanks for your answer. SwitchResX indeed is the solution that works.
    – Ilya Birman
    Aug 20, 2010 at 8:05
  • As of today, this is now a commercial product invalidating the answer.
    – leye0
    Feb 19, 2014 at 3:33
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    I find that this keeps the monitor active just blacks out the screen. It doesn't actually turn off the monitors.
    – Andy
    May 2, 2017 at 18:24
  • @Andy exactly, it also means that GPU still has to render the main screen, which makes my system slower overall when I connect to my 2 external monitors at home. It's really annoying. Though it still runs faster compared to just leaving it on
    – MuhsinFatih
    Dec 1, 2019 at 6:01
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Since SwitchResX is not free, I have developed a simple free alternative, that allows you to turn off a specific Monitor.

https://github.com/Eun/DisableMonitor/releases

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  • Is there a 10.8-compatible app for this?
    – yellow-saint
    Jul 15, 2014 at 20:04
  • I'am not sure if it works on 10.8 just try it out. Tell me if it works for you.
    – Eun
    Jul 16, 2014 at 7:11
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    Ok, I added a new Release for support 10.6+, please try this version.
    – Eun
    Jul 17, 2014 at 9:05
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    @BradParks, sorry for necrocommenting, but it may be a good idea to clarify to people that may stumble on this answer in the future: that "this software may cause damage" report apparently is related to this github issue. And honestly (and as some comments on that issue also point out) I find it extremely unlikely that a piece of software would cause this kind of damage (fry a thunderbolt port). It's more likely to be a coincidence, specially considering there was only this one report. It's kind of baffling the maintainer put that on README.
    – Fernando Figueiredo
    Sep 28, 2019 at 17:00
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    Didnt work on macbook pro 2020. While I tried to disable the external monitor, both of my display went off and it froze the touchpad as well. Didn't break anything for me, just had to force restart my computer. May be it is not supported to newer macos. An update would be very helpful. Thanks.
    – hsuk
    Sep 9, 2020 at 18:11
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+100

The only thing I can come up with which worked for me was to turn on mirroring (in the monitor menu in your menu bar, or in the screen preferences pane) and then turn off the secondary display. Spaces will then only show one display.

When you want it back (for watching movies, etc.), turn on the display and turn off mirroring.

This solution feels very kludgy to me, so I'm hoping there's a better answer (like 3rd-party software or a hidden pref which can be set via Terminal). But it should suffice for the short term.

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    My main display is 2560 at 1600, while plasma is 1920 at 1440, so if I enable mirroring, it will use the lowest for both. So this one does not work for me, unfortunately.
    – Ilya Birman
    Aug 22, 2009 at 5:23
  • I haven't tried this one yet, but does just turning off the plasma work?
    – John Rudy
    Aug 22, 2009 at 16:11
  • It does not, for me at least.
    – Ilya Birman
    Aug 23, 2009 at 8:10
  • I'll keep an eye out for software that might be able to take care of this, but if no one else has an answer at this stage, I'm fearing we might be at the end of the rope on this one. :(
    – John Rudy
    Aug 24, 2009 at 1:01
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    You can toggle it using an app, or command line tool too!
    – Brad Parks
    Apr 12, 2018 at 11:48
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mirror-displays is a command-line utility to toggle mirroring that works flawlessly for me on Catalina. It hasn't gotten an update in about 3 years but it still seems to be somewhat maintained.

Because it toggles mirroring on when you run it, then off when you run it again, I've set up a zsh alias in ~/.zshrc:

alias flippy="mirror && mirror"
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1

I found a different approach which works for my use case - showing a single monitor when connecting remotely to a multi monitor setup using Screen sharing.

All you have to do is enable "Display Mirroring", and the mac will automatically make it so all apps that were on different monitors are now on the one monitor.

More info in this similar question on AskDifferent stack exchange

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1

I use gfxCardStatus to force my laptop to only use the integrated graphics card. This doesn’t support external displays, which requires the discrete GPU.

I’m connected to a Thunderbolt 2 display, and everything else included the Ethernet works. Perfect for accessing the device from elsewhere using Apple Screen Sharing.

Note: It might be worth pointing out that 1) I have an Intel Mac and I don't know how the Apple Silicon devices behave, and 2) this means the discrete card isn't available for apps.

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  • So you are sating that using gfxCardStatus to force your MacBook to only use the integrated GPU would solve the core issue of “How do you disable a secondary display on a Mac?” since with only the integrated GPU in play the secondary display won’t show up in Spaces anymore?
    – Giacomo1968
    Sep 8, 2022 at 21:56
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    Yes, that's exactly what I'm saying: with the discrete card enabled the external monitor is active and I see both displays (scaled very small!) in Screen Sharing. With the integrated card enabled, the external screen remains off/asleep and I only see the laptop's built-in display in Screen Sharing. I've added two possible caveats as a note in my original post.
    – Clam
    Sep 15, 2022 at 19:02
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i'm dealing with the same issue

MBP 16" + 27" monitor on my desk, and the need to control it via remote desktop

Remote desktop is not easy to use with multiple monitor (you see only one at a time, you can't drag and drop between screens, you can't move windows between screens, etc)

Turning on miroring is a solution but i really would like to find a way to disable the external monitor

One solution, a weird one but i have no other solution at the moment, is to plug the monitor to a remote controlled electric plug, and to switch on/off this plug via an app wich can be scripted (a one clic solution)

It cost 5 to 10$ (or €) and a bit of work to make it "one-clic"

There can be some issue : the wifi need to be live, the plug need to work without bug, and some monitors need a physical press on their "power" button to wake-up

Maybe i'll try that one day

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-6

disconnect the second display and then click "detect displays" that did for me

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    That will work, but it doesn't answer the question. The questioner is looking for a solution "without actually unplugging it". Since it's a Mac Pro, the external display connector is likely not very accessible.
    – Doug Harris
    Aug 19, 2010 at 18:48

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