Installing macOS on your Mac computer involves downloading the macOS installer from the App Store, creating a bootable installer drive if needed, booting from the installer, selecting the target disk to install macOS, and going through the installation steps. This process usually completes without issues, but sometimes certain problems can prevent the macOS installation from fully completing.
Some common reasons for a failed macOS installation include insufficient storage space, incompatible or faulty hardware, corrupted installer files, drive formatting problems, and issues with the current macOS version being overwritten. Troubleshooting the specific error messages and issues you encounter is key to resolving installation problems.
Common Causes of Failed macOS Installation
There are several common reasons why a macOS installation may fail or encounter errors:
Insufficient storage space – The macOS installer requires a minimum of 8-10 GB of available storage space on the startup disk to complete installation. If your Mac’s startup disk is low on space, it can result in the installation failing.
Incompatible hardware – Apple designs each version of macOS to work with specific Mac hardware. Trying to install an incompatible version of macOS for your Mac’s model will fail. Check Apple’s documentation to verify your Mac model supports the macOS version you are trying to install.
Corrupted installer app – Sometimes download errors or interruption during the download can result in a corrupted installer app. Deleting the installer and re-downloading a fresh copy from the App Store can often resolve this.
Corrupted firmware – Firmware issues like corrupt NVRAM or SMC settings can also lead to failed installations. Resetting NVRAM and SMC before installing may help.
Time and date errors – The macOS installer requires the correct time and date to be set on your Mac. Incorrect time settings are a common cause of “An error occurred while preparing the installation” failures.
Third party software conflicts – Antivirus software, firewalls, VPN clients and other third party apps can sometimes interfere with the macOS install process. Temporarily disabling them may help.
Error Messages
During macOS installation, you may encounter various error messages that indicate the process was unsuccessful. Some common error messages include:
“An error occurred while preparing the installation” – This typically means your Mac couldn’t complete the installation due to insufficient storage space, incompatible hardware, or corrupted files. Restarting and trying again or booting to Recovery Mode to erase and reinstall macOS may resolve it.
“This copy of the Install macOS ________ application can’t be verified” – This occurs when the installer app is damaged or incomplete. Deleting the installer and downloading again from the App Store should fix it. Verify the new download’s integrity in Finder before retrying installation.
“Installation failed” with status code – Status codes like 1008F, 2001F, 2002F, 3000F indicate hardware/software incompatibilities. Checking Apple’s support guides to identify the specific cause is recommended.
“Not enough disk space” – Self-explanatory; you need more free storage space on the target disk to install macOS. Delete unused apps, files and run optimizations to clear space.
“macOS could not be installed on your computer” – General error that can occur from drive errors or incompatible/faulty hardware. Wiping the drive and reinstalling macOS may help isolate the problem.
Consult Apple’s list of common macOS and Mac update errors to troubleshoot messages not installing properly.
Checking Storage Space
Before installing macOS, it’s important to check that you have enough available storage space on your Mac’s hard drive. The amount of storage space required depends on the specific version of macOS you are installing.
For example, macOS Big Sur requires at least 35.5GB of available storage space [1]. Meanwhile, macOS Monterey requires at least 44GB of free storage [2]. In general, it’s recommended to have at least 15-20% free space available on your startup disk before installing macOS [3].
To check your available disk space on Mac, go to Apple menu > About This Mac > Storage. This will show you a breakdown of storage usage on your hard drive and how much free space is available.
If you don’t have enough free space, you’ll need to free up storage before attempting to install macOS. You can remove unused files and applications, store files on external storage devices, or upgrade your internal storage if needed.
Verifying Hardware Compatibility
Before installing macOS, it is crucial to verify that your Mac’s hardware meets the minimum requirements. Apple provides extensive resources to check compatibility, including detailed technical specifications for each macOS version and a list of compatible Mac models.
To find the system requirements, visit Apple’s macOS Catalina Technical Specifications page. This covers the processor, memory, storage, and graphics card needed. For example, macOS Ventura requires at least 8GB of memory and 20GB of available storage.
You can also use Apple’s compatibility checker to see if your specific Mac model supports the latest macOS. Models as far back as early 2015 can run Ventura, but older Macs may be limited to earlier versions like Mojave. Refer to Apple’s list of compatible Macs to verify your model.
If your Mac falls below the minimum requirements for processor, memory or storage, you may need to look into upgrading components before attempting to install the latest macOS release.
Downloading Latest Installer
One common cause of macOS installation failures is attempting to install an old, corrupted, or incompatible version of the macOS installer app. To avoid this, it’s important to download the latest stable installer directly from the App Store. The App Store ensures you get an official, uncorrupted installer signed and verified by Apple.
To download the latest macOS installer:
- Open the App Store on your Mac.
- Search for “macOS” and select the top result for the latest macOS version.
- Click “Get” and then “Download.” This will download the macOS installer app into your Applications folder.
Downloading directly from the App Store, rather than third-party sites, ensures you get a stable installer that hasn’t been tampered with or modified, avoiding potential installation issues. Having the latest installer also means compatibility with your Mac model and fixes for any bugs in previous versions.
Here are some official Apple Support links for downloading latest macOS installers:
How to download and install macOS
Apple – Support – Downloads
Creating a Bootable Installer
One way to troubleshoot a failed macOS installation is to create a bootable installer on an external USB drive. This allows you to perform a clean install of the operating system. To create a bootable installer, you will need a USB flash drive that is at least 12GB in capacity.
Use the createinstallmedia command in the Terminal app to make your USB drive bootable. The full command is:
sudo /Applications/Install\ macOS\ Catalina.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume
Replace “MyVolume” with the name of your USB drive. See this Apple support article for detailed steps.
The createinstallmedia tool will format the USB drive, make it bootable, and copy the macOS installer files to it. You can then boot from this USB drive on the problem Mac to perform a clean install or reinstall of macOS.
Performing a Clean Install
A clean install is the most thorough way to reinstall macOS and fix issues with a failed installation. Here are the steps to perform a clean install of macOS:
- Back up your Mac using Time Machine or another backup method. This will save your files and settings.
- Download the latest macOS installer from the App Store. Make sure it is compatible with your Mac’s model.
- Create a bootable USB installer drive:
- Insert a USB flash drive with at least 12GB of space.
- Launch Terminal and enter:
sudo /Applications/Install\ macOS\ Monterey.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume(replace “Monterey” with your OS name and “MyVolume” with your drive name).
- Restart your Mac and immediately press and hold Command-R to enter Recovery mode.
- In the Recovery window, select Disk Utility and click Continue.
- Select your startup disk from the sidebar and click Erase at the top. Choose APFS format and GUID partition scheme. Click Erase.
- Quit Disk Utility, select Install macOS, and click Continue. This will start the clean install process.
- Follow the onscreen prompts to select your disk and begin installation. Your Mac will reboot a few times during install.
- After install, you can restore data from your backup.
This complete clean install process will wipe your Mac and reinstall the operating system from scratch, fixing many issues from a failed update.
Troubleshooting Specific Issues
If you encounter a specific error message or issue when trying to install macOS, there are some common fixes to try:
If you see the error “This copy of the Install macOS Big Sur application can’t be verified. It may have been corrupted or tampered with during downloading,” try re-downloading the installer directly from the App Store. Corrupted or incomplete downloads can prevent installation.
For the error “An error occurred while preparing the installation,” try booting into safe mode and running the installer again. Safe mode loads a minimal set of macOS components which can bypass software incompatibilities.
If your Mac gets stuck on a progress bar when installing, allow it several hours to continue as the process can take a while. If it doesn’t progress, restart and try again. Failing drives or hardware issues can freeze an install.
For the message “This machine is not eligible for the requested build,” you likely have incompatible hardware. Check Apple’s requirements and your Mac’s specs. You may need an earlier macOS version.
With errors indicating low disk space, use Disk Utility to free up room on your startup drive by deleting unused apps, files, languages, and more. macOS installs need up to 20GB or more free space.
When to Seek Professional Help
In some cases, it may be necessary to seek professional assistance from an Apple technician or the Genius Bar to install or reinstall macOS. This is recommended when:
- You have attempted the installation multiple times with no success.
- The macOS installer cannot recognize or start up from your Mac’s startup disk.
- Your Mac won’t start up at all, even to macOS Recovery.
- You receive cryptic errors that are unresolved by support articles or online searches.
- A physical component of your Mac is potentially damaged or malfunctioning.
- You have attempted all other troubleshooting steps with no resolution.
In these cases, hands-on technical support can help diagnose any underlying hardware issues and perform advanced recovery options. Apple Geniuses have access to proprietary diagnostics tools and operating system installers that the average user does not. They can replace any failed components and potentially recover data from your original startup disk if needed.
While professional help comes at a cost, it may be the only way to get your Mac up and running again if you’ve exhausted all other options. The technicians can also advise whether your Mac may need to be replaced if any critical components like the logic board cannot be repaired.
