I have recently purchased a Dell S2340l monitor to extend my MBPr late 2013 screen. So far I can say it's a great monitor, colors are great, but still in the test phase...

Whatsoever, I really love that the MBP auto-adjusts the screen brightness depending on the light in the room. Therefore, my question: is there any possibility that this feature can be extend to the secondary monitor as well?

2 Answers 2


Lunar is a macOS app that can do exactly that.

Its Sync Mode can detect the automatic brightness changes that macOS does to the built-in display, and sync those changes to the external monitors in a way that the perceived brightness is matched across all monitors.

Disclaimer: I am the developer of Lunar

  • 1
    What a crazy set of great and useful apps. KUDOS
    – mrmut
    Commented Feb 9, 2023 at 7:07
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    7+ years after I posted this question, your answer made my day. Very well done sir :clap: :clap:. Considering that you are in Brasov and I am in Bucharest, we should meet for a coffee lol Commented Feb 11, 2023 at 21:52

I don't know about auto adjustment but the way around is you can creat a sort cut or using this app you can change it if there no hard button or program available for you monitor. Use this app. You can adjust brightness and also set shortcut for it



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    This app that you've linked really doesn't address the OP's question / need, which is to have the external monitor AUTOMATICALLY adjust brightness based on the light in the room... just like the built in screen does.
    – Charlie74
    Commented Dec 18, 2015 at 21:35

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