Does it seem like your Mac is running slowly? It’s always possible that you need more RAM, a speedy SSD to replace a slow spinning drive or even a new Mac. But you might just have a rouge app that’s hogging your Mac’s CPU. Here’s how to figure out if that’s the problem.
The key is in your Activity monitor bundled right into every Mac. Open your Applications folder and scroll down until you see the Utilities folder. Open that to find and double-click Activity Monitor. Activity Monitor can seem a bit hectic because it lists every “process” running on your Mac. You’ll see processes for activities like Mail and Safari, some apps use multiple processes and macOS itself relies on a ton of processes at once as well.
Notice in the picture below, at the top of the Activity Monitor there are buttons that provide access to different views: CPU, Memory, Energy, Disk and Network. Those views show the impact each process has on those aspects of the Mac. For now, I’ll focus on the CPU view that’s the default, but if you were trying to figure out why your MacBook Pro’s battery was draining so quickly, you’d look in the energy view for example.
At the bottom of the CPU view is a graph of CPU load, and numbers that correspond to how much of that load comes from the system and much from the (apps you’ve launched). As long as the sum of those numbers stays under 100% most of the time, you’re probably fine. But if you’re near or at 100%, you’ll want to hunt for rogue processes.
To identify them, click the % CPU column header to sort the process list by CPU power. If necessary, click again to change the direction of the sort so the arrow next to % CPU is pointing down, so those processes using the most CPU power are at the top. Be aware that the percentages in this column are by core (unlike the graph and numbers at the bottom), so a runaway app on a 4-core iMac could claim to be using as much as 400%in the % CPU column.
Now watch the list for a while. If one of the processes is sucking CPU power, you’ll see it at the top of the list. If it matches an app you’ve launched, quit that app to give other apps a chance at the CPU. That often solves your problem quickly. In the most extreme case, the process name will be in red, which means it’s not responding, at which point you can force quit it by selecting it and then clicking the X button at the left of Activity Monitor’s toolbar.
Equally likely, though, is that the top process will be one you don’t recognize immediately, like backupd (Time Machine). mds or mdworker (spotlight), photolibraryd or photoanalysisd (Photos), or kernel_task_ or WindowServer (core mac OS functionality). You can’t (or at least shouldn’t) quit these processes manually, but at least you’ll know that things are slow due to a Time Machine backup running, Spotlight indexing new files etc. If one of these processes has gone nuts, the best solution is to restart your Mac.
If you can’t identify a single rogue app, or if the slowdown doesn’t seem to be related to any app, you might just need to have your Mac evaluated by a service technician or it just might be time to upgrade to a new Mac