Apps can keep a Mac from going to sleep if their functionality calls for it. A browser may prevent an app from going to sleep if it’s downloading a file. Similarly, an app that is playing media may also prevent macOS from entering the sleep state since users will not interact with the device while watching something. These types of apps are obvious examples but if you suspect an app is keeping your Mac from sleeping, but you cannot figure out which one it is, you can check Activity Monitor.
View apps keeping Mac awake
Open Activity Monitor. You can open it from the Launchpad, or you can use Spotlight search to launch it. Go to the Energy tab and you will see a column called ‘Preventing Sleep’. Look through this column and if there’s an app entry that reads ‘Yes’ in this column, it is preventing the Mac from sleeping. The screenshot below shows that the Mac isn’t being kept awake.
We ran an app called Amphetamine which is a popular app for keeping Macs awake. Once the app was running and active, we returned to the Activity Monitor and sure enough, it was listed in the Energy tab as an app that was preventing the Mac from going to sleep.
If you find an app is preventing sleep there are a few things you can try. First, check what the app is doing. If it’s an activity that will be interrupted should the system go to sleep, wait for the activity to complete or cancel it if that’s an option.
If the app isn’t doing anything that would require your Mac to remain awake indefinitely, check the app’s settings. Mac apps don’t accidentally prevent sleep so it’s possible the app has a setting that where it prevents sleep. If it does, you can turn it off.
If neither of the above two methods work quit and relaunch the app. It may fix the problem. You should also check if the app is actively communicating with another app and in doing so, preventing your Mac from going to sleep.
macOS runs a tight ship when it comes to sleeping a system. It runs on desktops as well as on MacBooks where battery life is important and therefore, it won’t allow the system to remain awake when it isn’t being used. To that end, it isn’t easy to force macOS to stay awake so if your Mac won’t sleep, there is definitely something behind it and not just a system fluke.