Sonoma - Clamshell mode

I have a 2019 MacBook Pro. I just upgraded to Sonoma (14.0) and am using clamshell mode via USB-C and a CalDigit docking station... Clamshell mode worked fine with Ventura - once engaged it would sleep and wakeup via keyboard... With Sonoma, I can enter into clamshell mode, but after the system goes to sleep, I cannot wake it up via keystrokes. I need to open the MacBook, wake it up by depressing the finger print key, then close to enter clamshell mode again... it's a pain!


I did not see anything in the release notes about this mode being inactivated...


Any one else experience this?


Thanks for the help.

MacBook Pro 17″, macOS 10.12

Posted on Sep 28, 2023 7:58 AM

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18 replies

Sep 29, 2023 1:43 PM in response to mdp41

In my case the external display is connected to the MacBook via HDMI. When the lid is closed the MB goes to sleep (black screen external monitor) and wake up is not possible with the external keyboard. The lid needs to be opened to get to the login screen. This is different from Ventura where the MB, external display and external keyboard would remain “on” when closing the lid.

Sep 29, 2023 2:56 PM in response to mdp41

The separate article that Used to describe how to use your Mac in closed-clamshell mode has been removed. Apple has been hinting for some time that they have no love for that feature.


Readers here are not likely to have any magic bullets for you . It is entirely possible it is no longer supported.


ask Apple support:.


Official Apple Support

Oct 4, 2023 12:49 AM in response to mdp41

OK, So while on the phone to Apple Support, I recognised that the battery icon was NOT showing that the system was running on mains power, but the battery instead.


Mains power being the operating power source is signified by the power plug looking icon being over the top of the battery icon.... not the lightning icon which signifies charging as it does on all devices...


Clamshell mode will not operate unless there is a mains power source if lid is closed.


This is why the extended display works on battery power, but drops off when you close the lid. Giving the impression that clamshell is the issue.


By unplugging my multi hub (bon.elk ELK-80029-R . An approved hub as it is sold at Apple in Australia) and reconnecting it to power, the mains power icon was present and the clamshell mode therefore enabled....


I'm no expert, but i believe there may be a compatibility issue between Sonoma and some multi hubs. Mains power not flowing through as it did on Ventura for some reason.


I'll monitor this and see if reseting the multi hub (disconnect and reconnect power) fixes the clamshell issue next time it occurs.


If so, i might try a new multi hub and see if that resolves the issue.


If others can please confirm the above and suggest a multi hub which has worked well for them that would be great??

Oct 4, 2023 2:23 AM in response to dpcalleja85

In my case the MacBook Pro '21 (MB) is charging according the battery icon in the status bar. However, the MagSafe 3 charger LED in the connector remains red iso green during charging.


Anyway, still while charging, clamshell mode does not work. When closing the lid, the external display which is connected through HDMI, enters standby mode. So no video signal is coming from MB.


Replacing the MagSafe 3 charger with a USB-C charger doesn't show any difference. Closing the lid still brings the external display into standby mode.

Oct 4, 2023 8:46 AM in response to ZeoN-PowerTec

I was having an issue with my 2019 16" MacBook Pro and my 4K LG monitor where the screen was staying blank when in clamshell mode after upgrading to MacOS Sonoma, but I found a solution on Reddit from two years ago that solved it! Maybe it'll help someone else too. (I was also having an issue where the external display wasn't working at all, even when not in clamshell mode, but that's another story.)


Here's the solution that worked for me, edited a bit to apply to Sonoma and what worked in my specific situation:


  1. Open your MacBook lid so you're in dual screen mode.
  2. Open the "Displays" tab in System Settings.
  3. Choose your external monitor to view its settings. Then click "Advanced" and toggle on "Show resolutions as list."
  4. Hover your mouse over the resolution that says "(Default)" next to it. For me it was 1920 x 1080.
  5. Close your MacBook lid, and go into clamshell mode. Don't move your mouse/trackpad--the cursor needs to stay in the same place.
  6. Give your MacBook a few seconds to make sure it's in clamshell mode.
  7. Then click your mouse/trackpad.


As long as the display settings window stayed in the same place, and as long as you didn't move your mouse around, you will have been able to select the default option for clamshell mode even though you couldn't see anything on your external monitor. After doing that, the screen should come to life!


The first time I tried this, clicking my mouse on the blank screen in the place where the default resolution was supposed to be didn't seem to work, so I opened my MacBook back up and noticed the Settings window was gone, so I closed and opened Settings back up and tried again, clicking a bit sooner too, and then it worked! It made everything larger at first, since the default resolution/size for this 4K monitor was 1080p, but after choosing that and my screen coming back to life, I was able to switch back to the 1440p size setting, and everything works now as it should! :)

Oct 13, 2023 1:23 PM in response to mdp41

I got some new monitors and encountered the same issue. I seem to have solved it by making one of my external monitors the "main" one - which is done by moving the dock to it (by navigating to the monitor with your mouse and then keep moving "down" at the bottom, and the dock will show up).


After doing that, I closed my MacBook and the monitors did not go to sleep - clamshell mode is working great now.

Nov 1, 2023 3:12 AM in response to mdp41

I tried Kadzzy's solution, no dice, I'm using a Dell 2K external monitor on hdmi. Nothing has changed in my setup, including the adapters, and clamshell mode was dead since the upgrade to Sonoma. I read in another post however (I don't remember where, reddit I think) about getting the OS to "Detect Displays" - with the new preferences panel, you now need to do the following:


1) connect external display.

2) open Displays preference panel.

3) press the 'option' key.

4) the "Night Shift" button now becomes the "Detect Displays" button, you press this.

5) Make sure the Macbook is charging/waiting to chargae (lightning bolt on the battery icon or powerplug icon on the battery icon).

6) close the laptop lid.


For some unknowable reason, this worked for me. Either it was remembering a display configuration incorrectly, or there's been an update to the hdmi version that's confused things.


A co-worker had a similar problem, but he was using a charger that wasn't providing enough power, and the macbook would sleep when in clamshell mode. It was intermittent because this was happening only when he had an external hdd connected, and it was just enough to throw him over the threshold. He switched to a 90w power supply from 60w, and he was okay.


Good Luck

Sonoma - Clamshell mode

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