MacOS’s Activity Monitor will give you a list of all the apps you’re running, which is useful for closing down CPU-hungry processes. But it also throws in a bunch of system process, some of which may not be safe to quit. Here’s how to tell the difference.
Who Are All These Users?
First, you should look at who owns the process. Processes in macOS (and any other Unix-like operating system, including Linux) have owners, tying each process to the user account that started the process. And while you will recognize your user account, there’s a lot of other users on your computer, most of which are managed by the system.
You can see here, on a standard installation of macOS, there are over 250 users managed by the system, most of which start with an underscore:
Macs have so many user accounts because of the way permissions work in macOS, and each user has specific permissions. For example, _dock would have permission to access files related to the dock and not much else. This keeps your system more secure by keeping low-level system processes in their own containers.
Important: Since most of these are purely system processes, it’s best never to quit any process whose owner starts with an underscore.
It’s probably safe to close all processes under your user account name since most of them will automatically restart if they’re needed. However, you shouldn’t go too crazy closing everything to save on system performance, as the vast majority of the processes running on your machine are idle. It’s a lot better to leave them there for when they’re needed, instead of spending extra resources having to open them up again.
Processes with an icon next to their name denote apps, which are usually safe to close. You can sort by “% CPU” to view the apps taking up the most resources:
Some of these, like Google Chrome, will have helper processes used to improve performance. You’ll want to quit apps like Chrome from the Force Quit menu (Option-Command-Escape) rather than from Activity monitor.
One thing to note is that if the app has either of the two icons seen below, you should be more careful when closing it:
The icons to watch out for are a white sheet with a pencil, brush, and ruler in the shape of an “A,” or a shield.
The first is the default icon for an app without one, which may mean it’s a background process that doesn’t need a user-facing icon. The latter is an icon specific to user-level Apple processes, like Siri, Finder, and the Dock.
What is “root”?
Next up is root, which is the user account with the most system permissions. This is a weirder one because most of the root account’s processes system processes, but a few things you launch will launch as root—particularly things that need to access low-level system resources. These are harder to spot, as you’ll need to know what you’re looking for:
Here’s an example: ckb-next is a third party driver for my Corsair USB Mouse, so I know that ckb-next-daemon, running as root, is a helper process for that app. Were I to close it, my mouse would stop working. Generally, if you see something you recognize running as root, it might be safe to close, but most of the processes in this category are system things you shouldn’t touch.
Under the View menu in the top menu bar, you can change which processes will show up. You can choose to view only processes that have windows, which will show the same list as the Force Quit menu. You also can see processes started by you, by the system, and ones that are active or have gone inactive.
The useful part of these filter views is that you can then sort by “% CPU” on top of that. For example, you could view the longest running system processes by choosing “System Processes” as the filter and “CPU Time” as the sort.
Whatever you choose to quit, you can’t really harm your Mac by doing so, as whatever damage you may do can be fixed with a simple restart. In fact, the best way to clean up the process list is to restart your computer, which will clear out some unnecessary things. Look for apps that start running right as you log in and uninstall the ones you don’t need.