Why is my Mac so slow?

The two-minute check

1. Open Activity Monitor: press Command-Space, type Activity Monitor and press Return. Click CPU, then click the % CPU column header until the biggest numbers are at the top. Anything that stays near the top for half a minute is slowing everything else down.
2. Click Memory and look at the Memory Pressure graph at the bottom. Apple’s meanings: green, your Mac is using its memory efficiently; yellow, it might eventually need more; red, it needs more memory than it has. Swap Used next to it is disk space standing in for memory.
3. Open System Settings, General, Storage. The bar at the top shows how much space is left on the startup disk.
4. Click Disk in Activity Monitor if the Mac stalls while opening files: it shows which processes are reading and writing the most.

% CPU counts each core as 100%, so one process can show 150% or more on a Mac with several cores. A high Memory Used number on its own is normal; Apple says free, unused memory doesn’t by itself make a Mac faster. Memory Pressure is the number to watch.

Common causes, and what to do

An app or a browser tab using the processor

A runaway app, a heavy web page or a background job leaves less of the chip for what you’re doing. Busy tabs show up under the browser’s name; in Chrome, the ⋮ menu, then More tools, then Task manager shows which tab.

What to do: close the tab or quit the app. If it won’t quit, select it in Activity Monitor and click the Stop button (the X in the toolbar). Apple’s list also says to quit apps you aren’t using.

Not enough memory for what’s open

When apps need more memory than is free, macOS compresses memory and then swaps to the disk, and everything feels laggy: switching apps, typing, scrolling. Yellow or red memory pressure, and Swap Used that keeps growing, are the signs.

What to do: quit apps and close tabs you don’t need; the Memory tab sorted by Memory shows the biggest. If it’s red with your normal set of apps, the Mac needs more memory than it has. Apple’s page shows how to check whether yours can be upgraded: hold Option, choose System Information from the Apple menu, then Memory.

The startup disk is almost full

Low free space on the startup disk is the first cause on Apple’s list. macOS needs room for swap, caches and updates. See Why is my Mac storage full? for what’s taking the space and how to free it.

Slow with plenty of storage

Then it isn’t the disk. Go back to the CPU and Memory tabs: a busy process or yellow memory pressure is the usual answer. If both look calm, read on.

Slow all of a sudden, or right after an update

After a software update or upgrade, Spotlight re-indexes the Mac, which Apple says can take hours or even days. It shows up as mds, mds_stores and mdworker in Activity Monitor. Photos also analyzes your library in the background. Leave the Mac plugged in and awake until it’s done. A sudden slowdown on any other day is usually one new busy process, which the CPU tab shows.

Too hot, so macOS holds it back

When a Mac gets hot, macOS slows the processor to cool it down. If kernel_task is near the top of the CPU list, that’s happening: Apple says it makes the CPU less available to the processes using it intensely. It isn’t the cause; the busy app under it is. See Why is my Mac so hot?

Apps that aren’t made for your Mac

Apple lists incompatible apps as a cause. On a Mac with Apple silicon, apps built only for Intel run through Rosetta; Activity Monitor’s Kind column (right-click the column headers to add it) shows Apple or Intel for each process. Check whether the developer has a newer version.

Too much starting at login

Apps that open at login or run in the background take memory and CPU from the start. Open System Settings, General, Login Items & Extensions, remove what you don’t need from Open at Login, and review what’s allowed in the background.

Still slow

• Restart. It clears out whatever has built up since the last one.
• Install macOS updates from System Settings, General, Software Update.
• Run First Aid on the startup disk in Disk Utility: Apple lists disk problems as a cause.
• Start up in safe mode once. It doesn’t load login items or third-party extensions, so if the Mac is quick in safe mode, something that starts with it is the cause.

Apple silicon and Intel Macs

• Safe mode starts differently. Apple silicon: shut down, hold the power button until startup options appear, select the startup disk, then hold Shift and click Continue in Safe Mode. Intel: hold Shift right after you turn it on, until the login window.
• Rosetta only exists on Apple silicon. On an Intel Mac, every app runs without translation.
• MacBook Air with Apple silicon has no fan, so when it gets hot it slows down instead of getting louder. A slowdown during a long export on an Air is often just that.

Keep an eye on it from the menu bar

Activity Monitor answers “which app” once you open it. Multimeter keeps the totals in the menu bar, so you see the slowdown coming:

• CPU: total use across all cores, every 3 seconds on power. Yellow above 70%, red above 90% by default.
• Memory: the same Memory Used figure Activity Monitor shows, as a percent of your Mac’s memory; its menu says, for example, “12 GB of 32 GB”. Yellow above 80%, red above 90%. Multimeter doesn’t show memory pressure or swap, which are the better signs of trouble; Activity Monitor’s Memory tab has them.
• Disk space: how full the startup disk (or any drive) is, warning at 85% full and critical at 95%.
• Thermal pressure: whether macOS is slowing things down to stay cool.

Each meter can send a notification when it goes critical. Five live meters use about 3% CPU, and they pause while the displays sleep. Multimeter shows totals, not per-app lists.