Updating your Mac takes long enough as it is. But that ordeal becomes even more time-consuming when the update fails and an error message says “macOS could not be installed on your computer.”
Don’t lose hope. Most of the time, you can fix this error using the troubleshooting steps below. It shouldn’t take long to work your way through them. We’ll even explain how to avoid these kinds of macOS errors in the future.
Why macOS Couldn’t Be Installed on Your Computer
There are a lot of different reasons a macOS installation might fail. Hopefully, the error message told you exactly what the problem is. That way, you know where to target your troubleshooting efforts.
Some of the most common reasons macOS can’t complete the installation include:
- Not enough free storage on your Mac
- Corruptions in the macOS installer file
- Problems with your Mac’s startup disk
- Incompatible hardware
Whatever the cause of your macOS installation error, it’s usually easy to fix for yourself. Follow the tips below to sort out the issue.
Before Troubleshooting Your macOS Installation Error
If your macOS installation couldn’t be completed, you might find yourself stuck in a loop where the installer reopens every time you restart your computer. Follow these quick steps to break out of that loop and protect your data before troubleshooting the error.
Step 1. Boot Up Your Mac in Safe Mode
Safe Mode stops various programs from launching upon startup, including the macOS installer. Booting your Mac in Safe Mode breaks you out of any startup loops and stops troublesome programs from running in the background.
To boot into Safe Mode, restart your Mac and hold down the Shift key while it powers on. Release the key when you see the Apple logo or hear a startup sound. It should say Safe Boot in the menu bar on the login screen.
Step 2. Create a New Backup Using Time Machine
It’s always important to back up your Mac before installing a major macOS update. These updates edit the core files in your operating system, so if something goes wrong you might need to completely erase your Mac to fix it.
Connect an external drive and use Time Machine to back up your Mac . Time Machine is the simplest way to protect all your data in incremental backups. These allow you to restore files from particular dates instead of keeping only the latest version of everything.
Step 3. Check Your Mac’s Compatibility in the App Store
Before getting started with our troubleshooting tips, take a moment to make sure the latest version of macOS is compatible with your Mac.
Open the App Store on your Mac and search for the version of macOS you want to install (for example, “macOS Catalina”). Click that app to view its details in the App Store and scroll down to the Information section.
Beneath Compatibility, the App Store tells you whether that software Works on this Mac or not. If it isn’t compatible, you can’t install that macOS version upgrade. It might be the first of many signs that it’s time to replace your Mac .
What to Do When the macOS Installation Couldn’t Be Completed
Now that you’ve backed up your Mac and made sure it’s compatible with the latest version of macOS, it’s time to try fixing your installation error with the troubleshooting tips below.
Since there are so many potential causes to this macOS error, any one of these suggestions might fix the problem. We’ll start with the quickest and easiest tips to save you as much time as possible.
1. Restart Your Mac and Retry the Installation
Sometimes, all you need to do to fix macOS errors is to restart your Mac and try again. Open the Apple menu at the top-left of your screen and select Restart from the dropdown menu to do so.
If your Mac is unresponsive, press and hold the Power button to force a shutdown. Don’t do this while the installation is in progress, though, since doing so can corrupt the files in your operating system.
2. Set Your Mac to the Correct Date and Time
It’s possible that the date or time on your Mac is wrong. When this is the case, it can lead to problems connecting with Apple’s servers, which might be the reason there was an error installing macOS.
Open the System Preferences and go to Date & Time to correct it. Click the Padlock and enter your administrator password, then choose to Set date and time automatically.
3. Create Enough Free Space for macOS to Install
A typical macOS installer takes up around 4-5GB of space on your Mac. But to complete a macOS installation, your computer actually needs about 20GB of free storage.
This is because the macOS installer needs extra space to unpack files and folders. Without that additional free space, the installer has no room to work and can’t complete the installation on your Mac.
Open the Apple menu and go to About This Mac > Storage to view the amount free space on your Mac. Click Manage Storage to see what’s using the most space and then follow our tips to free up more storage on your Mac .
4. Download a New Copy of the macOS Installer
The macOS installer on your Mac may have become corrupt somehow. It’s a good idea to move that installer to the Trash and download a new one to replace it.
We suggest you download your macOS installer directly from Apple’s support website. This way, you get the full combo installer, rather than the smaller version available through System Preferences or the App Store.
5. Reset the PRAM and NVRAM
The PRAM and NVRAM store various settings and preferences on your Mac, such as your screen brightness, sound volume, and display resolution. Errors with your PRAM or NVRAM might explain why macOS couldn’t be installed on your computer.
Fortunately, it’s easy to reset these settings without erasing any of your personal data. To do so, restart your Mac and hold Option + Cmd + P + R while it powers on.
Keep holding all those keys until you see a second Apple logo or hear a second startup sound, at which point the reset is complete.
6. Run First Aid on Your Startup Disk
Still seeing that the macOS installation couldn’t be completed? There might be disk permission or fragmentation errors on your startup disk. It’s easy to fix most of these kinds of errors using the Disk Utility app, which comes pre-installed on macOS.
Open Disk Utility from the Utilities folder in Applications. Select your Mac’s startup disk in the sidebar—usually called “Macintosh HD”—then click First Aid. When you Run First Aid, Disk Utility scans your disk for errors and repairs whatever it can.
7. Use Recovery Mode to Reinstall macOS
If macOS still won’t install properly, you might need to reinstall the whole operating system instead. You can do this using Recovery Mode on your Mac.
Restart your Mac and hold Option + Cmd + R while it powers on. Release the keys when you see an Apple logo or hear a startup sound, at which point a macOS Utilities window appears. Click Reinstall macOS to install the latest version of macOS.
This might take a while, since your Mac needs to download the new software first.
8. Erase Your Mac and Restore From a Backup
The last troubleshooting solution for any software-related problem is to erase your startup disk and reinstall macOS from scratch. With a new version of macOS on your computer, you can then restore all your data from a Time Machine backup.
If you don’t back up your Mac before you erase the startup disk, you will lose all your data: photos, music, files, and everything else.
Follow these instructions to erase and restore your Mac .
Use These Mac Utilities to Avoid Future macOS Errors
As you’ve seen, there are several reasons an error message might say macOS could not be installed on your computer. We’ve shown you how to troubleshoot these problems, but you have a better chance avoiding them if you keep your Mac in tip-top shape all the time.
Lots of free apps claim to help you do this. They offer to free up more storage or remove malware, but you shouldn’t be too quick to trust them. Take a look at our list of the best free Mac utilities that you can trust. Use them to find and resolve future issues before they ever become a problem.