To launch Activity Monitor, type the application’s name into Spotlight or Launchpad. You can also find the application at “Applications -> Utilities -> Activity Monitor.app.”
Getting Acquainted with Activity Monitor
In the default view, Activity Monitor provides a table of all the currently-running applications and the amount of CPU “space” they’re taking up. It doesn’t just show user applications either – you’ll also see system processes and daemons, which is huge. You can’t easily see that information in many other places in macOS. Activity Monitor provides some much-needed visibility into what the heck your computer is doing.
At the top of the window you’ll find five tabs: CPU, Memory, Energy, Disk and Network. These tabs show resource use data for each of those categories. Click on a category to reveal the list showing their current allocation by process.
Along the bottom of the window you’ll see a graphical representation of the current resource allocation and some high-level statistics. For CPU you’ll see a split between system processes and user processes. As you change tabs, this graph will change to reflect relevant information.
Force-Quitting Applications
The most common use of Activity Monitor is probably force-quitting applications. Since Activity Monitor lets you see everything that’s currently running, it makes it easy to quickly identify applications that have hung or crashed and need to be put out of their misery. For easy identification, a hung application’s name will turn red, and the text “Not Responding” will appear in parentheses. This lets you know you need to force quit the application.
To do so, click on the application name and click the “Force Quit” button. You can also right-click on the application name and choose “Force Quit” from the context menu.
Finding Runaway Applications
Like any table view, you can click the name of a column to sort by that column’s criteria. For example, clicking “% CPU” will sort applications by the percentage of the CPU’s capacity that they’re using.
This quickly reveals resource-hogging applications and can reveal run-away applications that are using more than their fair share of system resources. If you notice that all your fans have suddenly started spinning, for example, you can review this sorted list for likely culprits.
Is It Time for More RAM?
Buying more RAM isn’t as popular as it once was for Macs since users can’t really upgrade it themselves anymore. However, if you’re buying a new Mac, checking the memory tab of Activity Monitor will help you figure out if you need more memory than you currently have. Click the “Memory” tab up top and take a look at the graph at the bottom of the window.
You’re looking for the Memory Pressure graph on the right. If that’s yellow or red, that means your system is running low on memory. You also want to check out the “Swap Used” field at the bottom of the center column. If that’s a high number, it means you computer is constantly using slow hard disk storage to fill in for insufficient memory. That slows your system down significantly, and it probably means you don’t have enough RAM to support your current workflow. If you see something more like the screenshot below, you’re in good shape.
Free Up Memory
Of course, if you can’t get more RAM, you can also quit RAM-hogging applications from Activity Monitor. Click the “Memory” column to sort by the most memory-intensive applications and then start shutting things down.
Find Applications Using Internet Bandwidth
If your Internet connection has suddenly ground to a halt, it might be because applications are using more than their share of bandwidth. Click the “Network” tab up top to reveal a table showing how much communicating each of your applications is doing. You can sort by “Sent Bytes” or “Received Bytes” to see which apps have been the most active.
Conclusion
Activity Monitor will help you keep a better handle on what your system is up to behind the scenes. If your computer is suddenly running slowly, you can figure out why and take the necessary steps to fix your workflow.
