You leave your laptop and, coming back, find it still brightly lit or at least on? Find out here how to investigate which applications, processes or browser tabs may be at fault and preventing sleep on a Mac.
First, Give Me Your Hand and Swim
If you are a sea otter, you lie back and drift in a lake’s waters to—sleep.
If you are a sea otter, you also spend most of your time alone—except mating season, of course. Then, you tend to hold on to your neighbors, especially during sleep, and can be seen famously asleep holding hands drifting through the lake.
Now, this might raise suspicions why sea otters so far have been neglected as mascots for any version of OS X or macOS… when sometimes they, too, only sleep when you hold their hand. Let’s find out what keeps your Mac awake:
How to Find Out What App Is Preventing Sleep on a Mac
Using Activity Monitor
Time needed: 5 minutes
To find out which application, process, thread, or Safari tab is preventing your Mac from sleeping using Activity Monitor:
- Open Activity Monitor.
Where: You can find Activity Monitor in the /Applications/Utilities folder, or under Other in Launchpad.
Search: A quick way to launch Activity Monitor is through Spotlight, of course; press Command Space, start typingacti…, and select Activity Monitor. - Go to the Energy tab.
- Ensure the Preventing Sleep column shows.
No such column: Select View | Columns | Preventing Sleep from the menu if you cannot see it.
Only active: Select View | Active Processes to see all (and only) processes that are currently active and most likely to prevent sleep. - Look for Yes in the Preventing Sleep column.
Dig down: Do expand applications with sub-processes (such as Safari) to see their preventing sleep.
Sort by sleep prevention: Click the Preventing Sleep column header to put all the applications that keep your Mac from going into sleep mode on top.
With Safari, you can identify the very tab or window that is preventing sleep using Activity Monitor. With other browsers such as Firefox or Google Chrome, look for media playing if the application as a whole shows Yes for Preventing Sleep.
Looking for a bit of the opposite? How to turn off the screen on a Mac (without sleeping it)
Find Out What Is Preventing Sleep Using Mac Terminal
You can also—and more precisely—find out what processes are stopping your Mac from entering sleep mode, and what prevent the display from turning off using the Terminal prompt:
- Open Terminal.
- Type
pmset -g. - Press Enter.
- Find the delays for entering sleep and turning off the display as well as which processes prevent either in the following lines:
– sleep: if any processes prevent sleep mode, they will appear as (sleep prevented by ___).
– displaysleep: Processes stopping the screen from turning off appear as (display sleep prevented by ___).
Turn off the screen: You can still turn off the display manually, of course.
To see detailed information about the assertions:
- Type
pmset -g assertionsat the Terminal prompt. - Press Enter.
Assertions: You can also pull up an ongoing log of new sleeping blocks as they happen withpmset -g assertionslog.
How to Find Out What App Is Preventing Sleep on a Mac: FAQ
I see lots of “Safari Web Content (Cached)” processes taking up memory; can I quit them?
While it is not necessary to do so, you can safely close these processes:
- Highlight all processes you want to quit.
In a sweep: Hold down Command to select multiple processes or Shift to select a range; click the Process Name column to sort by name.
Find them: Press Command Control F and type(Cached)to see only the cached Safari processes. - Select View | Quit Process from the menu.
- Select Quit (you do not need to force quit these processes).
Will the Chrome Task Manager help me identify which page is preventing sleep?
No, unfortunately it will not.
As the tab at fault will typically be playing media, your best bet is Chrome’s media hub. To see which tabs play media:
- Click the media hub button next to the Chrome address bar.
- See the tabs and windows with media, paused or playing.
Do I have to use the Energy tab in Activity Monitor?
No, you can add the Preventing Sleep column to any Activity Monitor tab.
(How to find out what app is preventing sleep on a Mac tested with macOS Sonoma 14.2, Ventura 13.1, Monterey 12.0, Big Sur 11.0, and Catalina 10.15; updated January 2024)