Why is my Mac so slow? How to find the cause

Start here: a five-minute diagnosis

Rather than trying twenty tips, find out which resource is running short; that tells you which fix will work. You need Activity Monitor (in Applications › Utilities, or press Command-Space and type "Activity Monitor") and System Settings.

1. CPU. In Activity Monitor, click CPU and sort by % CPU. Is something near the top that you aren't using? The figure is per core: a single busy thread reads about 100% (we checked on macOS 27.0.1), so values above 100% are possible on any Mac with several cores. The Idle figure at the bottom is the share of the processor nothing is using.
2. Memory. Click Memory and look at the Memory Pressure graph at the bottom. Green is fine; yellow and red mean memory is short.
3. Storage. Open System Settings › General › Storage and look at how much space is available.
4. Heat. Is the Mac hot, are the fans loud, and is kernel_task high in the CPU list? That's your Mac slowing itself down to cool off.
5. Timing. Did it start after a macOS update, a migration to a new Mac or a big photo import? Then background indexing is the likely cause.

Whichever check stands out is the one to fix; the sections below follow the same order. Apple's own list (If your Mac runs slowly) is similar: low free space, an app that needs more memory, apps not made for your Mac, unused apps left open, and disk problems.

A busy app or process

If one app sits at the top of the CPU list while you're not using it, quit it normally first (File › Quit, or Command-Q). If it won't respond, select it in Activity Monitor, click the Stop button in the top-left corner of the window and choose Quit or Force Quit. Apple notes that Force Quit can lose unsaved work in files the app has open (Apple, Quit an app or process).

If the busy process is part of macOS, its name usually tells you what's happening:

• WindowServer draws everything on screen. See What is WindowServer?
• kernel_task high, with a warm Mac, means heat management. See What is kernel_task?
• mds_stores and mdworker_shared are Spotlight indexing. See What is mds_stores?
• photoanalysisd and mediaanalysisd analyze your photos. See What are mediaanalysisd and photoanalysisd?

An app that keeps returning to the top usually needs an update, or has a setting (sync, indexing, previews) that keeps it busy. For the other columns, see how to read Activity Monitor.

Memory pressure, not "free memory"

A Memory Used figure close to the total is normal: macOS keeps recently used files in spare memory to speed things up, and hands it back when an app needs it (Apple, View memory usage). Watch the Memory Pressure graph instead. Green is fine; Apple says yellow means your Mac "might eventually need more RAM" and red means it needs more (Apple).

When pressure is yellow or red, macOS compresses memory and swaps to disk, and everything feels sluggish. Sort the Memory tab by Memory and quit the biggest app you don't need, or close browser tabs. If you'd like a number, this Terminal command is read-only and shows how much swap is in use:

sysctl vm.swapusage

It prints one line such as vm.swapusage: total = 6144.00M used = 5211.94M free = 932.06M (encrypted). Some swap is normal; a large, growing figure while pressure is red is the sign. On Apple silicon the memory is part of the chip package and is chosen when you buy the Mac, so if pressure is red every day with your normal apps, the lasting fix is running fewer heavy apps at once.

Not enough free storage

Low free space on the startup disk is the first cause on Apple's list. macOS needs room for swap, caches and updates, and it slows down when it runs short. Check System Settings › General › Storage; the categories and the recommendations there are the safest place to start (Apple, Free up storage space on Mac).

Apple doesn't publish a minimum amount of free space, so treat any figure you read online as a rule of thumb rather than a spec. The practical signs you're too low are a red or nearly full bar in Storage settings, updates that won't install, and apps that fail to save. See how to free up space safely, and What is System Data? for the most confusing category.

Heat: your Mac slows itself to cool down

When the processor gets too hot, macOS limits how much of it busy apps can use. In Activity Monitor this shows up as kernel_task using a large share of the CPU. Apple explains that kernel_task does this to manage temperature, doesn't cause the heat itself, and backs off once things cool down (Apple, If kernel_task is using a large percentage of your Mac CPU). The fix is the source of the heat: quit the heavy app, keep the vents clear, use the Mac on a hard surface rather than a bed or cushion, and keep it out of direct sun. Why is my MacBook so hot? goes through the causes.

Background work after an update or migration

After a macOS update, a migration or a large import, macOS often re-indexes files for Spotlight and analyzes your photo library. Both can keep the processor busy for hours. For the People & Pets album, Apple says Photos on a Mac does its detection while you aren't using the app, and that it can "take up to a few days" depending on the size of your library (Apple). Leaving the Mac plugged in and awake, with Photos closed, gives it the chance to finish. See Spotlight indexing and photo analysis for how to check progress.

Too much starting at login

Apps that open at login, plus the helpers and updaters that run in the background, all compete for memory and processor time, and they're why a Mac can feel slow for the first few minutes after you log in. Open System Settings › General › Login Items & Extensions. Remove apps you don't need from Open at Login, and switch off helpers you don't recognize in the background section, which is called Allow in the Background on macOS 15 Sequoia and App Background Activity on macOS 26 Tahoe and macOS 27. How to stop apps opening at startup covers the helpers Settings doesn't show and which ones are safe to turn off.

Browser tabs and extensions

Every open tab can run scripts, play media and refresh in the background, and every extension runs on the pages you visit. A heavy page often shows in Activity Monitor under a helper's name rather than the browser's: Chrome's tabs run as Google Chrome Helper (Renderer), and Safari's pages run in WebKit processes. Close tabs you're not using and review extensions. In Safari, choose Safari › Settings, click Extensions and deselect the ones you don't use (Apple, Use Safari extensions on your Mac). In Chrome, open chrome://extensions.

Out-of-date apps and macOS

Updates often fix the runaway behavior that slows a Mac down. Check System Settings › General › Software Update for macOS, and the App Store for its apps (Apple, Keep your Mac up to date). Apps you downloaded from the web usually have a "Check for Updates" item in their app menu; see updating all your apps.

Apps built only for Intel processors run on Apple silicon through Rosetta translation. To find them, select an app in Finder, press Command-I and check Kind: "Application (Intel)" needs an update. On macOS 27 there's also a list in System Settings › General › About › Intel-based Apps. Apple says that from macOS 28, Rosetta will only work for certain older games, so these apps are worth replacing now (Apple, Using Intel-based apps on a Mac with Apple silicon).

What doesn't help

• Cache cleaners. Caches exist to make apps faster. Clearing them frees disk space for a while, then apps rebuild them, and things can be slower until they do. It's worth doing only when you're short of space. See how to clear cache, and when not to.
• "RAM cleaners". Forcing memory empty throws away the cached files Apple says are there to improve performance, and your Mac then reads them back from disk. If memory pressure is green, there's nothing to fix.
• Resetting NVRAM or the SMC. Apple says the NVRAM reset steps don't apply to Apple silicon "and aren't needed" (Apple), and that the SMC resets automatically; a restart does the job (Apple). More in Mac maintenance on Apple silicon.

Still slow? Safe mode, a new user account, then Apple

If none of the checks above points anywhere, narrow it down:

1. Restart. It clears swap and stuck processes, and it's free.
2. Try safe mode. On a Mac with Apple silicon, shut down, then press and hold the power button until "Loading startup options" appears. Select your startup disk, hold Shift and click Continue in Safe Mode. You'll see "Safe Boot" in the menu bar at the login window. Safe mode helps show whether software that loads at startup is the cause (Apple, Start up your Mac in safe mode). If the Mac is noticeably quicker there, look at login items and helpers.
3. Try a new user account. Add one in System Settings › Users & Groups with Add User. If the Mac is fast in the new account, the cause lives in your own account (login items, an app's settings), not in macOS or the hardware.
4. Check the disk. Apple lists disk problems as a cause. Run First Aid in Disk Utility.
5. Contact Apple if it's slow even in safe mode and in a new account.

How Tend helps

Tend puts the first three checks on one screen. The free Overview gives a 0 to 100 health score with plain-language findings, and Energy & Apps lists the busiest apps by CPU, memory and estimated watts, with Quit and Force Quit, plus 24 hours of history so you can see what was busy before the slowdown. Startup Items, also free, shows what starts with your Mac and switches helpers off reversibly. With Pro you can slow a heavy app down by running it at low priority, and on macOS 26 or later with Apple Intelligence, Ask Tend answers "why is my Mac slow right now?" from your Mac's own readings.

Questions

Related guides

Sources

• Apple, If your Mac runs slowly
• Apple, View memory usage in Activity Monitor on Mac
• Apple, Check if your Mac needs more RAM in Activity Monitor
• Apple, Quit an app or process in Activity Monitor on Mac
• Apple, Free up storage space on Mac
• Apple, If kernel_task is using a large percentage of your Mac CPU
• Apple, If you can't find pets in the People & Pets album in Photos (how long photo analysis takes)
• Apple, Use Safari extensions on your Mac
• Apple, Keep your Mac up to date
• Apple, Using Intel-based apps on a Mac with Apple silicon
• Apple, Reset NVRAM on your Mac and Reset the SMC of your Mac
• Apple, Start up your Mac in safe mode
• Apple, Login Items & Extensions on macOS 15 and on macOS 26

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