Macs, whether they’re Macbooks or iMacs, or a Mac Mini are used with external monitors. The features on macOS tend to work almost flawlessly if you’re using Apple manufactured hardware but anything that hasn’t been manufactured by Apple, or that doesn’t carry its stamp of approval may, or may not work with all of macOS’ features. Night Shift is a feature that was added a while ago to reduce blue/white light on the screen by tinting it a warm color. It’s a great feature but it seems that it doesn’t always work with external monitors. Here’s how you can fix Night Shift not working on external monitors.
Fix Night Shift for external monitors
There are three different ways you can fix this problem. It is highly unlikely that it is a hardware related problem so unless you have an exceptionally old, square monitor, Night Shift should work on your external monitors.
The first fix you should try, and this tends to have a high success rate, is to disconnect the monitor from your Mac, and then connect it again. Make sure Night Shift is turned on when you do this. When you connect the external monitor again, it should be tinted a warmer color. To that end, you should also examine the cable and any connectors you’re using to connect the monitor to the Mac. If they’re damaged, they may be interfering with the feature.
This fix is solely for MacBooks. Run the MacBook in clamshell or closed-display mode. This often leads to Night Shift being triggered on the external monitor. Once Night Shift starts working with the external monitor, you can run your MacBook with the lid open if you want.
Nocturnal is a free, open-source app that allows you to control Night Shift from the menu bar. It can basically turn on Night Shift without you having to go through the System Preferences app and it works great with external monitors. Download Nocturnal and run it. Allow it to tint your external monitor and let it run for a while. Disable it, and then enable Night Shift. This will likely fix Night Shift not working with the external monitor. You can remove the app if you want but it does give you a great, quick way to manage the tint of the screen directly from the menu bar so there’s no harm keeping it around.
One of the three fixes here should force enable Night Shift on your external monitor. If the first trick is what did the job but you have to keep repeating the step each time you boot to your desktop, you should try getting new cables/connectors.