When connecting my 2017 15' macbook pro to a 4k external monitor it gets a little bit warmer (65° celsius, while it's only at 35 without the monitor) than I want it to be, even if it's just idling. Since I don't ever use the macbook screen as a secondary screen when connected, I thought I might turn it off completely and hopefully cool the machine down a little bit. Is there any way of doing this? I figured out I could just set the brightness to 0 but will this prevent the machine from actually rendering images?

  • I use an external apple 27" display with an external keyboard and mouse and I just close the macbook - everything continues just fine ...
    – Solar Mike
    Sep 30 '17 at 14:56
  • I thought about this as well but then again I'm worried that the display might get too hot as it directly covers the hottest spot. Sep 30 '17 at 15:36
  • Runs cooler - I used to use both at the same time either mirrored or extended and found it got hot - graphics working hard so went to just external and its fine and definitly 20 or so degrees cooler can tell by the fans as well
    – Solar Mike
    Sep 30 '17 at 15:41

If the idea was to just hide doubled picture on laptop display, you can just lower brightness level to 0 using fn + F1

  • This is the solution I went with. I have one external monitor so I set the display arrangement to Mirror Displays, then turned the brightness of the built-in monitor down to 0. Oct 17 '19 at 20:53

There is a possible ay to accomplish this you can first click on System Preferences by searching in spotlight or in the dock then click Misson Controls then Click on Hot Corners and click on one of the corners – it’s up to you which one. Once selected, pull down the menu next to it and choose Put Display To Sleep.Connect the external display to your MacBook and then move your mouse to the corner you selected above. It should turn off only the internal display. Close your MacBook lid and wait a couple of seconds. Lift the lid and it should stay off. You can use the trackpad and keyboard in this way as well.

  • 6
    I tried this - the 'Put display to sleep' hot corner sleeps all the displays, not just the internal one.
    – cam8001
    Jan 22 '18 at 22:17
  • 1
    This also puts all displays to sleep for me. I'm on macOS 10.14.6. Oct 17 '19 at 20:52

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