Why is my Mac so slow? 10 checks that find the cause

By Anil Gautam · Updated 4 October 2026

A slow Mac almost always comes down to one of a few causes: one app working hard, too little free memory, background indexing after an update, heat, a nearly full disk, or a slow connection that only looks like a slow Mac. Work through these checks in order. Each one takes a minute or two, and you change only one thing at a time.

1. Restart if it has been days

macOS is good at running for weeks, but apps are not always as tidy. Memory leaks, stuck helpers and half-finished updates build up. If your Mac has been on for several days and everything feels sluggish, save your work and choose Apple menu › Restart. It is the cheapest test there is: if the Mac feels fast afterwards, the cause was something that built up over time, and you can watch for it to return.

If an app refuses to quit, a restart also clears it. WhySlow shows how long your Mac has been running and suggests a restart when an app is stuck or uptime is long.

2. Find the app that is working hard

Open Activity Monitor from Applications › Utilities. Choose View › All Processes, open the CPU tab and sort by % CPU. Watch for a minute. Launching an app, exporting video or installing an update produces a normal burst of work. What you are looking for is one app that stays near the top while you are not using it.

Numbers above 100% are normal on modern Macs: 100% means one full processor core, so a busy app can show 300% on a Mac with many cores. If one app stays busy, save your work and quit it normally, then reopen it and repeat the task. Updating the app often fixes a runaway process for good.

Some names at the top belong to macOS, not to an app. Don’t force-quit a system process just because its name is unfamiliar. kernel_task slows other work down when the Mac is hot. WindowServer draws everything on screen. mds_stores builds Spotlight’s search index. Look the name up first; the process library explains 85 of the most common ones.

3. Check memory pressure, not “memory used”

In Activity Monitor’s Memory tab, look at the Memory Pressure graph at the bottom while the slowdown is happening. macOS deliberately fills spare memory with cached files, so a big “Memory Used” number with green pressure is normal and healthy. Yellow or red pressure, a growing Swap Used figure and a delay when you switch apps together mean your Mac is short of memory for what you have open.

The usual culprits are many browser tabs, a virtual machine, a local AI model or a large creative app. Close one heavy thing you are not using and compare. Each Safari tab runs as its own com.apple.WebKit.WebContent process, so tabs add up quickly. Read what memory pressure, compression and swap mean before deciding you need more RAM.

4. Let indexing finish after an update or migration

After a macOS update, a migration to a new Mac, or copying lots of files, several background jobs start at once. Spotlight rebuilds its index with mds_stores and mdworker_shared. Photos scans your library for faces and objects with photoanalysisd. iCloud Drive syncs with bird and cloudd. Apple says Spotlight indexing can take hours or days, depending on how much there is to index.

These jobs run fastest when the Mac is plugged in and you are not using it. Leave it on overnight and judge the next day. If one keeps running for days, see each process page for what to check.

5. Keep your Mac cool

When a Mac gets hot, macOS protects it by giving kernel_task more CPU time so other apps get less. Activity Monitor then shows kernel_task using a lot of CPU, which looks like the cause but is really the cure. Apple explains this in its kernel_task article linked below.

Find the workload behind the heat: a video export, a game, a busy browser tab or a virtual machine. Use the Mac on a hard surface, keep the vents clear, and avoid sunshine and soft bedding. On a laptop, check System Settings › Battery: Low Power Mode trades some speed for less heat and longer battery life, and powerd manages it.

6. Tame browser tabs and extensions

A modern browser is often the heaviest app on a Mac. Every tab is its own process, and pages with video, chat apps or live dashboards keep working in the background. In Chrome, open Window › Task Manager to see which tab or extension is busy; in Safari, look for com.apple.WebKit.WebContent entries in Activity Monitor, then close tabs one at a time to find the busy page.

Close duplicate tabs, bookmark what you want to read later, and disable extensions you don’t use. Then compare. WhySlow’s Browser panel finds duplicate tabs across Chrome-family browsers and can close the ones you pick, after asking.

7. Trim login items and background helpers

Apps install helpers that start at login and keep running: updaters, sync clients, licensing services. One by one they are small, together they slow startup and use memory all day. Open System Settings › General › Login Items & Extensions and review both lists. Turn off what you don’t need; you can always turn it back on.

Updaters are a common example: Google Software Update and Microsoft AutoUpdate wake up regularly to check for new versions. They are harmless, but if an app is gone, its helper should go too. WhySlow lists background items and explains what each one belongs to.

8. Free up storage space

macOS needs free space for swap, caches and updates. When the startup disk is nearly full, everything slows down and updates can fail. Open System Settings › General › Storage to see what is using space and follow its recommendations. WhySlow warns when less than 15 GB is free.

Back up before deleting anything, and delete only files you recognize, such as old downloads, videos and disk images. Avoid deleting unknown files from System or Library folders. After you delete files, macOS may spend a little time catching up; deleted clears purgeable space and fseventsd records the file changes.

9. Install updates, then let them settle

Apple fixes performance problems in macOS updates, and app developers do the same. Check System Settings › General › Software Update and the App Store, and update the apps you use every day. While an update downloads and prepares, softwareupdated can be busy for a while.

After a major update, expect a day of extra background work (see check 4). If your Mac is still slow a few days after an update, that is worth reporting to Apple with details of what feels slow.

10. Make sure it is the Mac, not the connection

If typing, switching apps and opening local files feel normal, but websites, streaming and cloud apps pause, your Mac is probably fine and the network is slow. Try another website and another device on the same Wi-Fi. In Terminal, the built-in networkQuality command measures your connection’s speed and responsiveness.

Move closer to the router, or use a cable, and test again. Developers have extra suspects: a virtual machine, Docker or a runaway node process can use a lot of CPU and memory in the background. Docker Desktop lets you limit both in its Resources settings.

Still slow? Rule out software, then hardware

Start up in safe mode: it loads only what macOS needs and skips login items. On a Mac with Apple silicon, shut down, press and hold the power button until you see “Loading startup options”, select your startup disk, then hold Shift and click “Continue in Safe Mode”. On an Intel Mac, restart and hold Shift until the login window appears. If your Mac is fast in safe mode, something that starts at login is the likely cause; go back to check 7.

If it is slow even in safe mode, run Apple Diagnostics to test the hardware: on Apple silicon, hold the power button until startup options appear, then press Command-D; on an Intel Mac, restart and hold D. Take the result to Apple or an authorized service provider. If memory pressure is often yellow or red during your normal work, more memory may help; how much you can add depends on your Mac model.

How WhySlow speeds this up

Most of these checks mean reading numbers in Activity Monitor and searching for unfamiliar names. WhySlow does that reading for you: it samples your Mac’s activity, names the likely cause in plain English, explains every process, and suggests a specific next step. Explanations are free; one-click fixes cost $7 once.