Man using a MacBook with the "pinwheel of death" on the screen.

Is your Mac slow? Do you see the spinning pinwheel of death every day? Don’t put up with it! Here’s how to diagnose the issue so you can fix the problem.

How to Diagnose a Sluggish Mac

There are many reasons why your Mac might have performance issues. If you can figure out what’s wrong, you can take steps to rectify it. You can fix most common causes of a slow Mac yourself, and relatively easily. Here are some of the easier tips you can try to speed up your Mac.

Hardware issues, though, are the exception. If your Mac has a problem with a particular component, the fix becomes more complicated. Even desktop computers like the iMac are notoriously difficult to repair yourself—Apple uses heavy amounts of glue and solder in its manufacturing process.

In a worst-case scenario, you can always ask Apple to take a look. If you book a free Genius appointment at an Apple Store, they run a full set of diagnostics on your machine. From there, they should be able to recommend a fix for the problem. If you want Apple to repair your machine, you have to pay out of pocket if the warranty’s expired, unless you have AppleCare+.

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Remember, it’s free to book an appointment at an Apple Store, find out what’s wrong with your machine, and how much it will cost to fix. The company only charges you for repairs after it has your consent to make them.

RELATED: 10 Quick Ways to Speed Up a Slow Mac

App Crashes: How Software Can Slow Down Your Mac

When software isn’t working correctly, it can make your machine seem unresponsive. Sometimes, just the app that’s crashed exhibits this behavior; other times, misbehaving software might attempt to take your whole machine down with it.

If you suspect an app crashed, right-click its icon in the Dock, hold the Option key on your keyboard, and then click Force Quit. You can also use the keyboard shortcut Command+Option+Esc to force quit the current app.

If you’re not sure which app has crashed, or you think one crashed in the background, launch Activity Monitor. Click the “CPU” tab and view the “% CPU” column in descending order. This way, the apps using the most processing power appear at the top. If you spot anything using more than its fair share, click it, and then click the “X” to kill the process.

The macOS Activity Monitor.

Sometimes, performance issues are caused by memory leaks, where a particular task or process eats up all the available memory. To see the memory, click the “Memory” tab, and reorder the “Memory” column in descending to see similar results. You can kill processes the same way you would an app that’s crashed.

Processes that have completely crashed appear in red with the words “Not responding” next to them under Activity Monitor. You can kill these and restart them. If you encounter repeated issues with the same apps, you might want to consider using something else (or drop the developer an email).

Disk Space: Your Mac Needs Room to Breathe

Low disk space is another common cause of macOS slowdown. Without enough free space on your startup disk, macOS is unable to run maintenance scripts and background processes that keep your computer ticking along. Unfortunately, Apple doesn’t specify exactly how much free space is required to keep your Mac happy.

A general rule of thumb is to keep 15 percent of your startup disk free at all times. This figure applies mostly to laptops with small drives. An iMac with a 3 TB drive requires a much smaller percentage to satisfy macOS requirements. But it’s also much harder to fill up a 3 TB iMac than a 128 GB MacBook Air.

A macOS Storage Overview.

If you work with large files or create lots of temporary files (like for video or photo editing), you should keep as much free space on your drive as the total size of those temporary files.

To see how much free space you have on your Mac, click the Apple icon in the top-left corner, and then click About This Mac. Click the “Storage” tab to see a breakdown of your current disk usage. You can then free up space on your Mac.

System Resources: Are You Pushing Your Mac Too Far?

Your Mac has a finite number of resources available, limited by factors like processor cores, available RAM, and the presence of a dedicated graphics card. If you know how far you can push your Mac, it will help you avoid performance issues in the future.

Some common tasks that might push your Mac over the edge are:

  • Too many open tabs in your web browser.
  • Hungry software, like Photoshop, open in the background.
  • Playing graphically-intensive 3D games.
  • Working with huge video and photo files or rendering video.
  • Doing two or more of the above (or similarly intensive processes) simultaneously.

If you have hundreds of tabs open in a browser like Chrome, don’t be surprised if you encounter memory issues. If you switch to a Mac-optimized browser like Safari, it will help, but you still might need to curb your tab addiction.

Browsers, in general, can be a source of poor performance. Too many extensions and plugins negatively affect your browser’s responsiveness. And some web apps can tax your machine just as much as native ones. One example of this would be if you use a web-based spreadsheet tool, like Google Sheets, to crunch a lot of data.

The Activity Monitor CPU Load Graph.

To find out how your system is faring at any point, open Activity Monitor and check the “CPU Load” and “Memory Pressure” graphs on the CPU and Memory tabs, respectively.

Hardware Issues: Problems Under the Hood

Few computers hold resale value like a Mac. They’re built to last, and I can say that because I’m typing this on 2012 MacBook Pro. But problems can arise—particularly if your machine is showing its age. But there are some things you can check yourself.

Apple Diagnostics

Your Mac includes a basic diagnostic tool you can run yourself. Follow these steps to do so:

  1. Shut down your Mac.
  2. Press the power button to turn on your Mac, and then immediately press and hold D on the keyboard.
  3. When you see the screen that asks you to select a language, release the D key.
  4. Select a language, and then wait for the diagnostic tool to run.

Note: If Apple Diagnostics doesn’t start, try holding Option+D instead. You need an internet connection to do this because your Mac downloads Apple Diagnostics before it runs it.

Apple Diagnostics can only tell you so much in the form of a reference code. You can then check the reference code in Apple’s database, but don’t expect to learn too much. For example, you might discover there’s a problem with the computer’s memory, but you won’t know which stick of RAM is faulty or what’s wrong with it.

This tool is useful to rule out hardware issues, but it’s pretty useless for troubleshooting purposes. For a more detailed report, you’re better off booking a free appointment at the Genius bar. Of course, you won’t get detailed feedback about how to fix your Mac there, either.


You can check some components manually with the right tools. For example, MemTest86 is a free tool you can use to check your computer’s memory. Install it on a USB stick, start your Mac, and then run it. When you use a USB stick as the storage medium, you can test the RAM properly without the macOS overhead.

The memtest86 RAM health check software.


A failing drive can also cause issues. Most Macs have solid-state drives. These aren’t prone to failing abruptly the way standard hard disk drives are. Solid-state drives generally only fail after some advance warning. And when they do eventually die, data recovery is impossible. Follow the steps below to check the health of your SSD:

  1. Click the Apple logo in the top-right corner, and then choose About This Mac.
  2. Click System Report, and then choose Storage.
  3. Select your main drive (likely labeled “Macintosh HD”).
  4. Scroll down to “S.M.A.R.T. Status” and see what is written alongside it. If it says “Verified,” your drive is performing normally, with no issues. If it says “Failing,” this could be the source of your problems. Eventually, the drive will become “Fatal,” and you’ll have to replace it or your Mac.

A macOS System Overview SSD health check.

For a more detailed look at your drives, download DriveDx (it’s free to try). This utility should give you more information than Apple claims it will.

For ultimate peace of mind, be sure to back up your Mac regularly with Time Machine.


The CPU is the brain of your computer. There’s not a lot you can do to test it, though. If it’s not functioning correctly, you might encounter slowdowns, freezes, and sudden shutdowns. One way to glean more information is to benchmark it with an app like Geekbench. You can then use the Mac benchmark charts to see how it stacks up.

Geekbench Mac Benchmark Charts.

If your Mac has a dedicated GPU, you can test it with tools like Heaven or Cinebench. If your GPU has issues, you might notice unsatisfactory performance in 3D applications, onscreen artifacts and glitches, system freezes, or sudden shutdowns.

Unfortunately, there’s not a lot you can do to fix issues with the CPU or GPU. Any problems that arise there will likely require that you replace your Mac’s logic board. It usually makes more financial sense to just buy a new Mac rather than pay the premium to fix your old one.

Decline with Age: Is Your Mac Just Old?

Sometimes, performance issues have a very simple cause: age. As your Mac ages, expect its performance to decline. New software requires better hardware, while the hardware inside your Mac stays the same.

Most Mac owners shouldn’t encounter too many performance issues over the first three years or so of use. After that, things start to go downhill. Once you pass the five- or six-year mark, you’re going to have to consistently think about whether the software you run gets the most out of your machine.

About This Mac Overview for a 2012 MacBook Pro.

If you have an old Mac and you’d like to squeeze as much life out of it as possible, here are a few things you can try:

  • Switch to a lightweight browser. Safari is optimized for Mac, and it tends to offer better performance and lower energy usage than its rivals.
  • Favor Apple’s first-party apps. Like Safari, many Apple apps are optimized for macOS and Apple hardware. One striking example of this is Final Cut Pro, which drastically outperforms Adobe Premiere on older machines. You could also ditch Pages for Word, Lightroom for Aperture, or Evernote for Notes.
  • Be mindful of multitasking. Avoid overstressing the CPU or GPU unnecessarily. If you’re rendering a video, go make a cup of coffee until it’s done. If you have 100 tabs open, close 50.
  • Beware of outdated or sluggish software. Outdated apps might perform worse on modern macOS systems because they lack optimization. Avoid using Java-based apps that require the Java Runtime Environment, as it can tax the performance of your machine.
  • Keep macOS updated. Whenever possible, make sure your Mac is running the latest version of macOS. Apple focused on improving macOS performance over the last few iterations of its desktop and mobile operating systems. If your system isn’t up-to-date, you might be missing tweaks that could improve your experience.

When Should You Buy a New Mac?

The right time to buy a new computer is when you need one. If you’re encountering performance bottlenecks that prevent you from doing your job or doing the things you need a computer for, it’s time to upgrade.

If your machine constantly crashes or is sluggish due to a failing hardware component, it’s time to consider purchasing a new one. If you’re sick of juggling files and apps because your startup disk is too small, you might want to stop by the Apple Store.

Remember, your old Mac might still hold good resale value. Even ancient machines with problems fetch more money than you would expect. If you’re thinking about selling your old Mac, here are some tips to help you out.

Profile Photo for Tim Brookes Tim Brookes
Tim Brookes is a technology writer with more than a decade of experience. He's invested in the Apple ecosystem, with experience covering Macs, iPhones, and iPads for publications like Zapier and MakeUseOf.
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