Using Activity Monitor to Find What's Slowing Down Your Mac

When your MacBook feels sluggish, the fans spin up or the battery drains fast, guessing at the cause wastes time. Activity Monitor on Mac shows you exactly what's using your processor, memory, battery and disk in real time. Once you know how to read it, you can spot a runaway app in seconds. Here's a practical tour of the tabs that matter most.

How to open Activity Monitor

1. Press Command-Space to open Spotlight.
2. Type "Activity Monitor" and press Return.
3. Or open Finder and go to Applications > Utilities > Activity Monitor.

Across the top you'll see tabs: CPU, Memory, Energy, Disk and Network. Click any column header to sort by it.

CPU tab: what's working the processor

1. Click the CPU tab, then click the "% CPU" column so the highest numbers are on top.
2. Watch for an app that stays very high while you're not actively using it. That's often a stuck process, a busy browser tab or a sync tool.
3. To quit it, select the process and click the Stop button (the X) in the toolbar, then choose Quit. Use Force Quit only if Quit doesn't work, and save your work first.

Some system processes use CPU briefly after startup or an update, such as Spotlight indexing ("mds" and "mdworker") or Photos analysis. That's normal and settles down. Don't quit processes you don't recognize; look them up first. "kernel_task" using lots of CPU is often macOS managing heat, which is a clue to check for overheating. Our guide on MacBook overheating and loud fans explains more.

Memory tab: is your Mac running out of RAM?

High memory use alone isn't a problem, because macOS uses free RAM for caching. What matters is the Memory Pressure graph at the bottom:

• Green: memory is being used efficiently.
• Yellow: memory is getting tight; macOS is compressing data.
• Red: your Mac needs more memory than it has and is relying heavily on the disk.

Also look at "Swap Used". Large, growing swap with yellow or red pressure means your Mac is regularly short on memory. Closing unused apps and browser tabs is the quickest fix. On most modern MacBooks RAM can't be upgraded, so a constantly red graph is useful information when you choose your next Mac.

Energy tab: what's draining your battery

The Energy tab ranks apps by their energy impact. Check the "Avg Energy Impact" column to see what's been draining the battery over time, not just right now. Apps you rarely use but that rank high are good candidates to quit or remove from login items.

Disk tab: storage activity

The Disk tab shows how much data each process reads and writes. Heavy activity from backup, cloud sync or indexing is normal for a while. On older MacBooks with a spinning hard drive, constant disk activity is a common cause of slowness, and an SSD upgrade can make a dramatic difference. Running nearly out of space also slows things down, so keep some free storage available.

Turning findings into fixes

• Quit or uninstall apps that constantly use high CPU or energy.
• Remove unneeded items in System Settings > General > Login Items (or System Preferences > Users & Groups > Login Items on older versions).
• Keep fewer browser tabs open and remove unused extensions.
• Update macOS and your apps.

For more ideas, see our guide on how to speed up a slow MacBook.

Still slow? Get help in Ottawa

If Activity Monitor looks normal but your Mac is still slow, the cause may be an ageing drive, overheating or a hardware fault. Fix Revolution offers SSD upgrades, macOS reinstallation and hardware repair, with pickup and drop-off anywhere in Ottawa and Gatineau. Most jobs are done in 1–2 business days. For MacBook repair in Ottawa, get a free quote or call 613-265-4349.

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