How to check CPU and memory usage on a Mac

Check CPU usage

1. Open the CPU tab

   In Activity Monitor, click CPU at the top of the window.

2. Sort by % CPU

   Click the % CPU column header so the busiest processes are at the top. Watch for a few seconds. Short spikes are normal; something that stays high for minutes is worth a look.

3. Read the totals at the bottom

   System is CPU used by macOS processes. User is CPU used by apps you opened and the processes they started. Idle is capacity that isn’t being used. A mostly idle Mac is a healthy resting state.

4. Keep an eye on it from the Dock

   Choose View → Dock Icon and pick a CPU option to turn Activity Monitor’s Dock icon into a live CPU graph.

Check memory (RAM) usage

1. Open the Memory tab

   Click Memory, then click the Memory column header to sort the largest processes to the top.

2. Look at Memory Pressure first

   The graph at the bottom shows how well your memory is keeping up. Green means your Mac is using its RAM efficiently. Yellow means it might eventually need more. Red means it needs more RAM for what you’re doing right now.

3. Then read the breakdown

   The panel next to the graph lists Physical Memory, Memory Used, Cached Files, Swap Used, and the parts of Memory Used: App Memory, Wired Memory, and Compressed.

Memory pressure vs. “memory used”

Many people open the Memory tab, see that 15 GB of 16 GB is used, and assume something is wrong. Usually nothing is. macOS tries to put all of your RAM to work, because unused memory doesn’t make a Mac faster. Apple’s guide says this directly: having unused memory doesn’t necessarily improve performance.

Memory Pressure is the better signal. Apple describes it as how efficiently your memory is serving your processing needs, based on free memory, swap rate, wired memory, and file cached memory. A Mac with nearly all its memory in use and green pressure is doing fine. A Mac with yellow or red pressure is spending effort making room.

Here’s what the other numbers mean, in Apple’s terms:

• App Memory is memory used by apps.
• Wired Memory is memory the system needs to operate. It must stay in RAM and isn’t available to other apps.
• Compressed is memory macOS has compressed to make more RAM available. When memory gets tight, macOS compresses memory from inactive apps first. Compressing is faster than writing to disk, so some compressed memory is normal.
• Cached Files are files macOS keeps in otherwise unused memory to make things faster. macOS can reuse this memory for apps when they need it.
• Swap Used is space on your startup disk used to hold memory that doesn’t fit in RAM. Reading it back from disk is slower than RAM, so heavy swap use makes switching apps feel slow.

Check usage from Terminal

If you prefer the command line, top is built in.

• top -o cpu lists processes sorted by CPU use. Press q to exit.
• top -o mem sorts by each process’s physical memory footprint.
• sysctl vm.swapusage prints how much swap is in use.

For a friendlier interactive view in Terminal, see our comparison with htop.

Reading the list without guessing

Activity Monitor shows processes, which aren’t always the same as apps. A few patterns make the list easier to read:

• Helpers belong to their app. Browsers and Electron apps split work into helper processes. All the Google Chrome Helper (Renderer) rows add up to Chrome’s real total.
• System processes run your Mac. WindowServer draws everything on screen, and kernel_task is the core of macOS. High CPU in kernel_task can be macOS keeping the chip from getting too hot.
• Background indexing is temporary. mds_stores and mdworker are Spotlight. They often run hard after an update and then settle.

Our process library explains more names you might see. If your Mac already feels slow, start with this guide.