One of the reasons many of us use a Mac is that most of the time, to coin a well-worn phrase, it just works. We don’t have to spend hours dealing with driver updates, fixing problems caused by bloatware, or trying to get rid of viruses.

Occasionally, however, even on a Mac, things do go wrong. In this feature we explain the best ways to diagnose what the problem is and we share the best fixes for some of the most common problems.

In this article we look at the following, click on the link to jump to that section:

• How to fix a Mac that won’t turn on
• How to fix a Mac that won’t start up
• How to fix a Mac with a flashing question mark
• What to do if you see a grey screen at startup
• What to do if you see a blue screen at startup
• How to repair a disk with Disk Utility
• How to repair your boot disk/startup disk with Disk Utility
• How to repair disc permissions
• How to fix a Mac that won’t shut down
• How to fix a frozen Mac
• What to do if you see the Spinning Beach ball
• What to do if your Mac is running slowly
• What to do if a USB port isn’t working
• What to do if your WiFi is slow or not working
• What to do if your Bluetooth isn’t working
• What to do if your MacBook is not charging
• What to do if your Mac is running out of power too quickly
• What to do when your Macs fans are too loud and your Mac is overheating.Mac DIY repair guide.
• We also have a separate article about graphics issues with the 2020 iMac.

How to find out what’s wrong with your Mac

Sometimes it’s not immediately obvious what the issue is that is causing your Mac to misbehave so you will likely have to run through a number of steps to isolate what is causing the problem. These steps will depend on whether your Mac is even switching on, of course, and we look at how to fix a Mac that won’t start up next.

The check list of things to look out for when diagnosing the problem are as follows:

1. Note errors

Are you seeing an error message? If you are, write it down (or if it’s easier take a photo using your iPhone, or screenshot). We have this article including Common Mac error messages so check to see if it is covered there, or you could do a quick search in Google to see if anyone else is seeing the same error and if they fixed it.

2. Say when

Note when the problem started. Was it just after you had installed a new program or added a piece of kit? Had you recently performed a software update?

3. Check software

Speaking of software, is your software up to date? Check that you are running the most recent version of MacOS, it might be that you have encountered a known issue that has been fixed.

4. Check peripherals

Establish if a particular peripheral is causing the issue: unplug everything that’s plugged into your Mac and see if that solves the issue.

5. Check disk space

See how much disk space you have available. Go to About This Mac > Storage. We’d always advise that you have 10% of the total disk space free. If you need to free up some space read this: How to make space on your Mac.

6. Check Activity Monitor

This will show you if something is hogging memory or CPU. Go to Applications > Utilities > Activity Monitor (or click cmd+space and start typing Activity Monitor). Click on Memory to see if there is something hogging memory. Then click CPU to see if something is hogging the CPU. We look in more detail at memory hog issues and how to fix them with Activity Monitor below.

7. Run Disk Utility

Applications > Utilities > Disk Utility (or click cmd+space and start typing Disk Utility) to see if there is an issue with your disk. Read about How to use Disk Utility here. Note that Disk Utility had a bit of a makeover in Mac OS X El Capitan and some of the processes changed.

8. Start in Safe Mode

You may also be able to diagnose problems with your Mac if you start in Safe Mode. When you start up in Safe Mode your Mac will not load startup items and some software. The mode also performs a check of your startup disk so it should be able to alert you to problems. Read about starting your Mac in Safe Mode here.

After shutting down your Mac wait 10 seconds and then press the power button. As soon as your Mac starts (you may hear a start up chime) press and keep holding the Shift key. Once you see the Apple logo you can stop pressing Shift.

9. Start in Recovery Mode

When Apple introduced OS X Lion in 2010 it made some changes to the way that Recovery Mode works. If you are running an older version of MacOS the method will be slightly different (but we imagine that there aren’t many people left using that version now). Since Lion, when MacOS is installed on a Mac a Recovery HD volume is created on your Start Up drive. This volume (which is normally hidden) can be used to boot from if you need to do things like repair the startup disk, reinstall MacOS and more.

To restart in the Recovery HD you just need to press and hold cmd+R when you start up your Mac and keep holding those keys until the Apple logo appears. It can take a while to finish booting up. Once it has you will see a desktop with a window containing Utilities open.

10. Add a new user and troubleshoot

You could also create a new user profile and use that to isolate the problem.

Because a fresh account typically contains nothing that would already be corrupted, you can isolate whether a problem is in your everyday user account or a system-wide issue–maybe even hardware related. Read about how to do that here: Use a new user account to help isolate your Mac problem.

Once you have run though these steps you should have a clearer idea about the nature of your issue. Read on to find out how to fix it.

How to fix Mac start up problems

How to fix a Mac that won’t turn on

There are a number of reasons why your Mac might not turn on. Before you call your IT guy do make sure it’s plugged in.

If once you have checked that it is plugged in, made sure that there is power going to the screen, and that the brightness on the screen is turned up, you can follow these How to fix a Mac that won’t turn on tips to fix the problem.

How to fix a Mac that won’t start up

A Mac that won’t start up is a little different to a Mac that won’t turn on. When a Mac won’t start up it will often display something on the screen, or you will hear something inside whuring away.

You may see a flashing question mark or simply a blue or grey screen. We look at both of those occurrences below. We also discuss fixes for a Mac that won’t start up here.

How to fix a Mac with a flashing question mark

If you started up your Mac and were greeted with a folder with a question mark in the middle it might mean that your Mac’s disk has failed. But before you panic, there may be another explanation, and you may be able to fix it.

That folder with a question mark inside indicates that your Mac can’t find the startup disk and therefore can’t boot. Fixing this issue will involve putting your Mac into Recovery Mode and choosing the correct startup disk (which is likely to be your Macintosh HD, unless you want to boot from an external drive).

However if you aren’t seeing your startup disk, or you can’t select it, it may If it’s necessary to repair your disk. To do so you can use Disk Utility – Applications > Utilities > Disk Utility (or click cmd+space and start typing Disk Utility).

If you follow the tips in this article: How to fix a Mac with a flashing question mark you will hopefully be able to help your Mac find, or fix, the startup disk.

What to do if you see a grey screen at startup

A blank grey screen may indicate that there is a problem with a firmware update. A grey screen with an Apple logo in the middle may suggest that there is a problem with some software.

In the former case you need to ensure that your Mac firmware is up to date and that should be a simple case of checking that you are running the latest version of MacOS.

To actually start up your Mac so that you can check this you need to start in Safe Mode (and having done so you may find that if your Mac is restarted it starts up fine the next time). We describe how to start up in Safe Mode below.

Once you have started in Safe Mode you can find out if your MacOS software is up to date by opening the App Store app and clicking Updates.

If that doesn’t solve the problem you may need to repair your startup disk or disk permissions using Disk Utility. We describe how to do that below.

What to do if you see a blue screen at startup

If you see a blue screen, or a blue screen with a spinning beachball this may indicate that there is a problem with your software or a startup item.

You will need to start your Mac in Safe Mode. If despite adding your user name and password the Mac still doesn’t start up you may need to check your login items. We describe how to do this above.

If your Mac won’t start up in Safe Mode you may need to repair your startup disk or disk permissions using Disk Utility, the methods for both are described below.

We have an article on what to do to fix a Blue Screen of Death on a Mac here.

Repairing disks and running First Aid

How to repair a disk with Disk Utility

Disk Utility had a bit of a makeover in OS X El Capitan and as a result the way that you repair a disk has changed slightly. The steps you need to take will depend on the version of MacOS you are running. We’re going to assume you are running a version that is newer than El Capitan since that version of Mac OS X launched in September 2015.

1. Open Disk Utility (in Applications > Utilities, or cmd+space Disk Utility).
2. Select the volume you wish to run First Aid on. This could be a external hard drive (if it’s your own Mac hard drive you will need to jump to the next section).
3. Click on First Aid.
4. Click Run. This will start the verification and repair process.
5. When Disk Utility has run it’s checks you will see a drop-down sheet showing the status. You can click on the triangle at the bottom to see more information.
6. If no errors were found you will see a green tick at the top of the drop-down sheet.
7. If there were errors Disk Utility will attempt to repair them. (In older versions you had to manually choose Repair Disk).

If Disk Utility is unable to repair the drive, or it believes that the disk is about to fail it will warn you. Should this be the case you should back up your data before it’s too late. Read this article on backing up your Mac.

How to repair your boot disk/startup disk with Disk Utility

You can run First Aid on your startup drive as above, but if Disk Utility finds any errors it won’t attempt to fix them.

If you are wishing to repair your Mac’s startup drive (the boot volume) you won’t be able to as Disk Utility can’t repair the mounted volume (the one that everything is running from). In older versions of Disk Utility you will see that the Repair Disk option is greyed out.

In this case you need to start up in Recovery Mode and repair the disk from there. This way things can run from the Recovery HD volume that was created when MacOS was installed. (Note if you have a Fusion Drive things are even more complex).

1. To start in Recovery Mode press cmd+R when you start up your Mac.
2. Once your Mac has booted up you will see a Utilities screen. Choose Disk Utility.
3. Select the disk you wish to repair from the menu and clink on First Aid. As above Disk Utility will run its checks and try and repair if it can.

The repair process may take a while.

How to repair disc permissions

When Apple released El Capitan in 2015 it removed the ability to repairing disk permissions.

The removal of the feature probably indicates that repairing permissions was one of those solutions given that didn’t really do a whole lot of good.

It is still possible to repair permissions using Terminal, but we won’t go into that here, following Apple’s lead and assuming that it won’t do any good and might actually cause more issues.

How to fix shut down problems and unresponsive Macs

How to fix a Mac that won’t shut down

If your Mac isn’t shutting down it may be still closing apps in the background, the advice here is to be patient, sometimes it can take a while to shut apps if data needs to be saved.

However, there may be an issue with an apps that is stopping your Mac from being able to close. Look in the Dock to see if there is a bouncing app icon, that would indicate that something needs attention. Perhaps it’s just Pages or Word asking whether you want to save a file.

You may need to Force Quit if something is causing a hold up and can’t be fixed – beware you may lose some data though. We have advice on Force Quitting here.

If you can’t Force Quit, press and hold the power button until the Mac switches off.

Note that when you restart you Mac it may ask you if you want to reopen all the apps that you had open previously. We’d advise that you say no to this option just in case something you had open causes the same problem again if it reopens.

How to fix a frozen Mac

If your problem is that your Mac has frozen in the middle of a task, or an app has become unresponsive, it is possible to Force Quit it by right clicking/control clicking on its icon in the Dock and choosing Force Quit.

Alternatively you can Force Quit an app by pressing Command+Alt+Escape at the same time.

You can also press command+ctl+eject on your Mac laptop to force reboot. Or hold down the power button to achieve the same thing.

Be aware that if you have to Force Quit or reboot your Mac you may lose some data. If you have a Time Machine back up you may be able to recover the date from that. Here’s how: How to use Time Machine to recover data.

We also have an in-depth guide that explains how to fix a frozen Mac here.

What to do if you see the Spinning Beach Ball

The colourful ball that graces your screen whenever your Mac is struggling has a few names, Apple calls it the spinning wait curser, but we like to call it the spinning beach ball.

The ball appears when your Mac is trying to do to many things at once. Or more accurately, when an application can’t handle all the things it is supposed to do, the beach ball will start to spin. It’s a little bit like it’s saying it’s a little bit busy with something right now and will get back to you. Perhaps it is hinting that you might like to go and throw a ball around in the garden for a bit.

Usually the beach ball only appears on screen for a few seconds. When it doesn’t many refer to the Spinning Beach Ball of Death (kind of like the Blue Screen of Death on a Windows PC, but not nearly as fatal). Should you be seeing the beachball for longer than you’d like check the CPU and RAM sections of Activity Monitor to see if there is a hog (more on Activity Monitor in the next section).

Another reason you may see the beachball is if you are running out of space on your Mac. As we said above, we always recommend that you have 10% of your total disk space free. If you are getting to the point where space is at a premium then it can slow down your Mac because there is less space for swap files.

It may be that an application or process is causing the problem. Have a look in Activity Monitor to see if anything is being particularly greedy. You can quit the application or process there. (But as we said earlier, it it’s a Root process, don’t touch it).

One app that often calls up the beachball is Safari. If you see the beachball when you are surfing the web it may be that the webpage you are browsing is problematic. It’s name may well appear when you look at Activity Monitor, if if does then close that web page.

Mac performance issues

Mac running slowly

If your Mac is running slowly don’t download a program that claims it will speed up your Mac, the first thing you need to do is to try and find out what is causing the slowdown. Follow these steps to find out.

There are a couple of things you can look at in Activity Monitor. Open Activity Monitor (in Applications > Utilities > Activity Monitor, or by clicking cmd+space and typing Activity Monitor).

There are five different tabs along the top: CPU, Memory, Energy, Disk and Network.

To find out if something is hogging the power or memory click on Memory.

The resulting window displays a list of all processes running on your Mac, as well as a graph of memory usage. If it’s green, all is good with your system (although you may still benefit from closing a few memory hogs so read on).

If it’s amber or red, MacOS is having trouble managing memory and could be the reason that your Mac is running slowly. This could be due to a memory-hogging application. To find out which apps or processes are misbehaving, organise the list by memory usage (arrow pointing down), and you can identify the culprit.

Make sure you ignore processes that have “root” listed as the user column, and focus on applications running from your user account. Don’t quit ‘root’ processes.

If an application is using more memory than other applications you can close it by selecting the app and closing it from its menu, or by clicking on it in Activity Monitor and then clicking on the X icon at the top left of the menu.

In the block at the bottom of the table you can check how much memory (RAM) you have and how much memory is being used. If the reason your Mac is struggling is because you don’t have enough RAM available you can upgrade your RAM – find out how here: How to upgrade a Mac.

An app may also be causing issues if it is hogging a lot of CPU.

Click on the CPU tab and you’ll see information similar to that in the Memory tab. The graph at the bottom shows user (in blue) and system (in red) CPU usage.

If you see an application which is using a significant chunk of CPU cycles, quit it and you should notice a performance improvement in your Mac.

If a root process appears to be hogging the CPU, don’t just quit it, it’s usually a symptom of another problem. Google the process name and find out what it does. One regular culprit is ‘kernel_task.’ It represents MacOS’s kernel and handles lots of low-level tasks. If it’s using more than a few % of processor cycles, it could be that you’ve installed a system extension, or other software that accesses the system, which is causing a conflict.

Some users have reported that the MacBook Air, when the ambient temperature is very hot, runs very slowly and this shows up as ‘kernel_task’ hogging CPU cycles. In that case the only sensible solution is to move it somewhere cooler.

We also have this article offering a few more tips on how to speed up a slow Mac. And we have this tutorial on how to defrag a Mac (and why it’s not necessary).

WiFi is slow or not working

If you are having problems with WiFi, with your connection to the internet dropping or disconnecting at random, or simply not working at all, there are a few steps to take to try and solve it.

Start by turning the WiFi on your Mac off and on again.

See if that works, if it doesn’t we have a collection of tips for fixing WiFi problems here.

Bluetooth isn’t working

If you are trying to use a Bluetooth accessory, like a keyboard or mouse, or if you are trying to use a feature that requires Bluetooth, like AirDrop, you may encounter problems such as the Bluetooth Not Available error.

Start troubleshooting by restarting your Mac, sometimes that is all that is necessary to fix this problem.

Next turn your Mac’s Bluetooth off and on again. To do this click on the Bluetooth icon at the top right of your Mac’s the menu bar.

Try connecting your Bluetooth gadgets again.

If they won’t connect, turn your Bluetooth device off and on, and try connecting again.

Next try moving any other Bluetooth devices away that might be interfering.

If you are still experiencing issues, the next step is to remove some files from your Preferences.

Open the Finder and choose Go from the menu, then Go to Folder. Type /Library/Preferences and click Go.

Find the com.apple.Bluetooth.plist file and delete it.

Next go back to the Finder and select Go to Folder and type ~/Library/Preferences/ByHost. This time locate the com.apple.Bluetooth.xxx.plist file (note that after Bluetooth there will be a collection of random numbers and letters).

When you restart your Mac these files will be generated again, and will hopefully work properly!

If the issue is with the bluetooth device you might find the following useful:

• How to fix a broken Bluetooth mouse
• How to fix a broken Bluetooth keyboard

Power issues

MacBook not charging

If your Mac laptop isn’t charging here are a few things to try out:

Plug it in to a different socket just to rule out an issue with the power point.

Use a different power cable – see if a friend can let you borrow one. If it charges with a different cable you know that’s the issue. If you take the Mac and the cable to an Apple Store Apple is likely to replace the cable free of charge.

If your MacBook still doesn’t charge, check to see if your cable charges another Mac laptop, at least then you can rule out the cable being at fault.

If your Mac still won’t charge there are a few other tricks you can try before you take your Mac to an Apple Store for a genius to check.

First you could try resetting the SMC of your Mac. That’s the the System Management Controller. To reset the SMC, first you’ll have to shut down your MacBook. Once it’s off, connect the MagSafe power adapter and hold down Control, Shift, Option and the Power button for around four seconds, before releasing all at the same time.

After resetting the SMC, press the Power button to start up the MacBook and see if the problem has been fixed.

If that hasn’t fixed it, then your battery may be at the end of its life and you should take your MacBook to Apple for servicing.

Incidentally, if you have an old MacBook with removable batteries you can reset the battery by fully removing it and re-inserting it. Doing so may fix the issue – but based on the age of your machine it’s possible that it’s just reached the end of its life.

Mac running out of power too quickly

If you click on the battery icon in the menu bar at the top of your Mac you can see if any apps are using significant energy. If you are trying to squeeze a little more battery life out of your Mac on an day away from a power point then close those apps.

For more information about the most power hungry apps and processes take a look at the Energy tab in Activity Monitor (which was a new addition in OS X Mavericks).

Activity Monitor shows you how much energy all open apps are using as well as how energy usage has changed over time. You can also see if any running apps are actually taking advantage of Apple’s App Nap feature.

App Nap was a feature Apple introduced in Mavericks that allows inactive applications to go to sleep, reducing power usage and prolonging battery life.

Loud fans, Mac overheating

If your fans kick in there could be an issue that is causing your Mac to overheat, or you might have a faulty fan.

There are various things you can do to help your Mac run cooler, including placing it on a stand, closing the apps that are causing the processor to overwork, and apps that will allow you to stop the fans kicking. We have a detailed guide to what to do when your Macs fans get too annoying here.

Wondering how many years your Mac should last for? Read: How long do Macs last? 

We have a separate article where we discuss everything you need to know about getting Apple products repaired.