Softset

Performance

How to find which app is slowing down your Mac

Updated · Applies to macOS 14 Sonoma through macOS 27 Golden Gate

Short answer

Open Activity Monitor, sort the CPU tab by % CPU to find anything using a lot of processor time, then check the Memory tab's Memory Pressure graph: if it's yellow or red, look for the apps using the most memory. Quit or restart the worst offender.

“Slow” usually has one of three causes: something is using the processor flat out, the Mac has run short of memory and is swapping to disk, or the Mac is too hot and has slowed itself down. Activity Monitor can show you all three.

Open Activity Monitor

Press ⌘ Space, type Activity Monitor, and press Return. It’s also in Applications → Utilities.

1. Check the CPU tab

  1. Click CPU, then click the % CPU column header so the highest is at the top.
  2. Watch for a few seconds. A process at 100% means one full core; on a Mac with many cores, several hundred percent is possible.
  3. Note anything that stays high while you aren’t using it.

2. Check memory pressure

Click Memory and look at the Memory Pressure graph at the bottom. Green is fine, even if “Memory Used” looks high, because macOS deliberately uses spare memory. Yellow means it’s compressing memory to cope; red means it’s swapping to disk and everything slows. Sort by Memory to see what’s using the most. More in what memory pressure means.

3. Add up the helpers

Browsers and chat apps run many helper processes. Chrome can show dozens of “Google Chrome Helper (Renderer)” entries, one per tab or extension. Individually they look small; together they may be the biggest thing running. Choose View → All Processes, Hierarchically to see them grouped under their parent, or mentally add them up.

4. Check for heat

If the Mac is hot and slow and nothing is using much CPU now, it may be recovering from a heavy task. macOS reduces performance when it’s too hot. Keep vents clear, let it cool, and check the Energy tab for apps with high “Energy Impact”.

5. Check disk space

A nearly full startup disk slows everything, because macOS needs free space for swap and caches. Check System Settings → General → Storage. Aim to keep at least 10–15% free.

What to do about it