How To Fix It When MacOS Big Sur Installation Fails


Common Causes of macOS Big Sur Installation Failure

Installing a new operating system, such as macOS Big Sur, can be an exciting and beneficial upgrade for your Mac. However, sometimes the installation process doesn’t go as smoothly as planned. If you encounter installation failure, there are several common causes that could be contributing to the issue. Understanding these causes can help you troubleshoot and resolve the problem effectively.

1. Incompatible Hardware: One of the main reasons for installation failure is having incompatible hardware. Before installing macOS Big Sur, ensure that your Mac meets the minimum system requirements. Check if your Mac model is compatible with the new operating system.

2. Insufficient Storage Space: macOS Big Sur requires a significant amount of disk space to install. If your Mac’s storage is nearly full, the installation might fail. Make sure you have enough free space before proceeding with the installation.

3. Unstable Internet Connection: A stable and reliable internet connection is essential for a successful installation. If your internet connection is intermittent or slow, it can cause the installation to fail. Verify your network connection and try using a wired connection if possible.

4. Third-Party Security Software: Sometimes, third-party security software can interfere with the installation process. Temporarily disable any antivirus or firewall software before attempting to install macOS Big Sur.

5. Corrupted Installation Files: If the installation files for macOS Big Sur are corrupt or incomplete, the installation will likely fail. Verify the integrity of the installation files or try downloading them again from the official source.

6. Outdated Apps and Drivers: Ensure that all your apps and drivers are up to date before installing macOS Big Sur. Incompatible or outdated software can cause conflicts during the installation process.

7. Hardware Issues: In some cases, hardware issues such as a faulty hard drive or RAM can prevent the installation from completing successfully. Perform hardware diagnostics to identify and resolve any underlying hardware problems.

8. Insufficient System Resources: If your Mac doesn’t have enough available resources, such as RAM or CPU power, it can affect the installation process. Close unnecessary applications and processes to free up resources.

Remember to prepare your Mac for the installation by creating a backup of your data. This will ensure that your files are safe in case anything goes wrong during the installation process. Troubleshooting installation failures can be a complex process, but by identifying these common causes, you can take the necessary steps to resolve them and successfully install macOS Big Sur.

Checking System Requirements

Before attempting to install macOS Big Sur, it’s crucial to ensure that your Mac meets the necessary system requirements. Checking these requirements beforehand can save you from encountering installation failures and compatibility issues. Here are the key aspects to consider:

1. Compatibility: Verify if your Mac model is compatible with macOS Big Sur. Apple provides a list of supported Mac models on their official website. Ensure that your Mac is included in this list to avoid any compatibility issues.

2. Processor: Check the processor requirements for macOS Big Sur. It typically requires a 64-bit Intel processor or an Apple Silicon M1 chip. If your Mac has an older processor that is not supported, you may have difficulties installing the new operating system.

3. RAM: macOS Big Sur requires a minimum of 4GB of RAM, but Apple recommends having 8GB or more for optimal performance. Check the amount of RAM installed on your Mac and consider upgrading if necessary.

4. Disk Space: macOS Big Sur requires a significant amount of free storage space. Ensure that you have enough space available on your Mac’s internal storage before proceeding with the installation. Apple recommends having at least 35.5GB of free space for the installation.

5. Graphics Card: Verify if your Mac has a compatible graphics card for macOS Big Sur. Some features and graphical enhancements may require specific graphics capabilities, so it’s essential to check if your Mac meets these requirements.

6. Software Updates: Before installing macOS Big Sur, make sure your Mac is running the latest version of macOS Catalina or any other supported previous version. Applying any available software updates ensures that your Mac’s operating system is up to date and ready for the installation.

7. Internet Connection: A stable and reliable internet connection is essential for downloading the macOS Big Sur installer. Ensure that you have a fast and uninterrupted internet connection during the installation process to avoid any complications.

By thoroughly checking your Mac’s system requirements, you can ensure a smooth installation process and minimize the risk of encountering installation failures. It’s crucial to meet the minimum specifications outlined by Apple to ensure a compatible and optimized experience with macOS Big Sur.

Creating a Backup of Your Data

Before you proceed with the installation of macOS Big Sur, it is highly recommended to create a backup of your important data. This step is crucial because unforeseen complications during the installation process can result in the loss of your files. By creating a backup, you can easily restore your data in case anything goes wrong. Here are some essential steps to follow:

1. Choose a Backup Method: There are several backup methods available, including using Time Machine, cloud-based services like iCloud, or manually copying your files to an external hard drive. Choose the method that suits your preferences and needs.

2. Time Machine: If you have an external hard drive, using Apple’s built-in backup software, Time Machine, is a convenient option. Connect your external hard drive, go to System Preferences, and select Time Machine. Follow the prompts to set up Time Machine and start the backup process.

3. Cloud-based Backup: Services like iCloud provide automatic backups for specific files and settings. Enable iCloud backup by going to System Preferences and selecting Apple ID. Navigate to iCloud, then click on iCloud Backup and follow the instructions to enable automatic backups.

4. Manual Backup: If you prefer a more hands-on approach, manually copying your important files to an external hard drive is an effective method. Create a new folder on the external drive and copy your important files, such as documents, photos, and videos, into it.

5. Verify Your Backup: After the backup process is complete, it is essential to verify the integrity of your backup files. Make sure you can access and open the files from your backup location before proceeding with the macOS Big Sur installation.

Creating a backup provides peace of mind and ensures that your important data is protected. It allows you to restore your files in case of any unexpected issues during the installation process. Remember to keep your backup in a safe location, preferably separate from your Mac, to prevent potential data loss due to hardware failures or accidents.

Ensuring Sufficient Storage Space

One of the critical factors to consider before installing macOS Big Sur is ensuring that your Mac has sufficient storage space. macOS Big Sur requires a significant amount of disk space, and insufficient storage can lead to installation failures and other performance issues. To ensure a smooth installation process, follow these steps to free up space and make room for the new operating system:

1. Check Available Space: Start by checking the available storage space on your Mac. Go to the Apple menu, select “About This Mac,” and click on the “Storage” tab. It will show you how much space is currently available and what is taking up the most space on your hard drive.

2. Clean Up Unnecessary Files: Delete any unnecessary files, such as old documents, unused applications, and downloads. You can manually go through your files and folders or use macOS’s built-in tools like Finder’s Search feature or the “Storage Management” option in the “About This Mac” menu to identify and remove large files and applications.

3. Clear Temporary Files: Temporary files, caches, and system logs take up valuable space on your Mac. Use tools like CleanMyMac or Onyx to clear these files and optimize your storage. These tools can safely remove temporary files without deleting any critical system files.

4. Move Files to External Storage: Consider relocating large files, such as videos, photos, and music, to an external hard drive or cloud storage services like iCloud or Dropbox. This can free up a significant amount of space on your Mac’s internal storage while still allowing easy access to your files when needed.

5. Remove Language Files: macOS comes with language files for different languages, even if you only use one or two languages. Using a tool like Monolingual, you can remove unnecessary language files and recover substantial amounts of space on your hard drive.

6. Archive or Delete Old Emails: If you use the Mail application, delete unnecessary email messages or archive them to reduce the storage space used by your email client. This action can significantly free up space, especially if you have a large email archive.

7. Empty Trash: Remember to empty the Trash to permanently delete any files that you have previously deleted. These files still take up space on your hard drive until the Trash is emptied.

By ensuring sufficient storage space on your Mac before installing macOS Big Sur, you not only prevent installation failures but also optimize your system’s performance. Regularly maintaining a clutter-free hard drive will enhance your overall computing experience and allow for a smoother upgrade to the new operating system.

Fixing Internet Connection Issues

An stable and reliable internet connection is crucial for a successful installation of macOS Big Sur. If you’re experiencing internet connection issues during the installation process, it can lead to installation failures or slow download speeds. Here are some steps to help you troubleshoot and fix common internet connection issues:

1. Check Network Connections: Ensure that your Mac is connected to the correct Wi-Fi network or Ethernet cable. Double-check the network name, password, and any other authentication details. If you’re connecting through Wi-Fi, make sure you have a strong and stable signal.

2. Restart Modem and Router: Power cycle your modem and router by unplugging them from the power source for a few seconds, then plugging them back in. This action can help refresh the network connection and resolve any temporary issues.

3. Reset Network Settings: In some cases, resetting your network settings can resolve connection issues. Go to System Preferences, click on “Network,” select your active network connection, and click on the minus (-) button to remove it. Then, click on the plus (+) button to add it back and reconfigure your network settings.

4. Use a Wired Connection: If you’re experiencing a weak Wi-Fi signal or intermittent connection, try connecting your Mac to the router using an Ethernet cable. This can provide a more stable and reliable connection during the installation process.

5. Update Router Firmware: Check if there’s any available firmware update for your router. Updating the router firmware can address compatibility issues, improve network performance, and fix security vulnerabilities. Refer to the router manufacturer’s website or contact their support for instructions on updating the firmware.

6. Disable VPN or Proxy: If you’re using a Virtual Private Network (VPN) or proxy connection, temporarily disable them and try connecting directly to your network. Sometimes, VPNs or proxies can interfere with the installation process or cause connectivity problems.

7. Firewall Settings: Make sure your firewall settings aren’t blocking the necessary network connections for the installation process. Temporarily disable any firewall software or adjust the settings to allow the macOS Big Sur installer to access the required network resources.

8. Test with Another Device: If possible, check if other devices connected to the same network are experiencing any internet connection issues. If all devices are affected, the problem might be with your network provider or router settings. Contact your service provider for further assistance.

By following these troubleshooting steps, you should be able to fix common internet connection issues and ensure a stable network connection during the installation of macOS Big Sur. A reliable internet connection is crucial for a successful installation, so take the time to address any connection problems before proceeding.

Resetting SMC and NVRAM

If you’re experiencing hardware-related issues or encountering installation failures while installing macOS Big Sur, resetting the System Management Controller (SMC) and Non-Volatile Random-Access Memory (NVRAM) can help resolve some common problems. These two procedures can often fix issues related to power management, connectivity, and system settings. Here’s how to reset the SMC and NVRAM:

Resetting the SMC:

1. Shut Down Your Mac: Ensure that your Mac is powered off completely.

2. Disconnect Power: Unplug the power cord from the Mac and remove the battery if your Mac has a removable battery.

3. Press and Hold Keys: On a MacBook with a non-removable battery, press and hold the Shift, Control, and Option keys on the left side of the keyboard, then press and hold the power button simultaneously for 10 seconds. On a desktop Mac, unplug the power cord and wait for 15 seconds.

4. Reconnect Power: Plug the power cord back into your Mac if it was disconnected or reinsert the battery on a MacBook. Then, turn on your Mac by pressing the power button.

Resetting the NVRAM:

1. Shut Down Your Mac: Ensure that your Mac is powered off completely.

2. Press the Power Button: Turn on your Mac and immediately press and hold the Command (⌘), Option, P, and R keys together before the gray screen appears.

3. Keep Holding the Keys: Continue holding the keys until you hear the startup chime for the second time or see the Apple logo and progress bar appear and disappear for the second time.

4. Release the Keys: Let go of the keys and allow your Mac to boot up normally.

After resetting the SMC and NVRAM, check if the issues you were experiencing have been resolved. If the problems persist, it’s recommended to seek further assistance from Apple Support or visit an Apple Store for a more in-depth diagnosis.

It’s important to note that resetting the SMC and NVRAM should be done as a troubleshooting step and not as a routine maintenance task. Only perform these resets if you’re experiencing hardware-related issues or encountering problems during the installation process of macOS Big Sur.

Running Disk Utility

If you’re experiencing issues during the installation of macOS Big Sur, running Disk Utility can help diagnose and repair common disk-related problems. Disk Utility is a built-in utility on macOS that allows you to manage and troubleshoot your Mac’s storage devices. Here’s how to use Disk Utility to potentially resolve installation or disk-related issues:

1. Open Disk Utility: Launch Disk Utility by going to the “Applications” folder, then open the “Utilities” folder and select “Disk Utility.”

2. Select the Startup Disk: On the left sidebar of Disk Utility, select your startup disk or the disk where you want to install macOS Big Sur.

3. First Aid: Click on the “First Aid” button located in the toolbar or select “File” > “First Aid.” Disk Utility will check the disk for errors and repair them if necessary.

4. Wait for Verification: Disk Utility will start verifying the disk and displaying the progress. This process checks the disk for any issues, including file system errors or disk corruption.

5. Repairing Disk: If Disk Utility finds any errors, click on the “Repair Disk” button to attempt to repair the disk. If no errors are found, you can skip this step.

6. Checking Disk Permissions (Optional): You can also use Disk Utility to verify and repair disk permissions, although this feature is less relevant in newer versions of macOS. Select the disk in Disk Utility and choose “File” > “Get Info.” If there are any permissions issues reported, click on the “Repair Disk Permissions” button to fix them.

7. Restart Your Mac: After Disk Utility has completed the repair process, restart your Mac and attempt to install macOS Big Sur again. The repairs made by Disk Utility should help resolve any disk-related issues encountered during the installation process.

Running Disk Utility and repairing any disk errors can help ensure the integrity of your storage device and increase the likelihood of a successful installation of macOS Big Sur. However, if the installation issues persist or Disk Utility encounters problems it cannot repair, it is recommended to seek further assistance from Apple Support or visit an Apple Store for professional help.

Repairing File Permissions

In some cases, file permission issues on your Mac can cause difficulties during the installation of macOS Big Sur. Repairing file permissions using Disk Utility can help resolve such issues and ensure that the necessary files are accessible for installation. Here’s how to repair file permissions:

1. Open Disk Utility: Launch Disk Utility by navigating to the “Applications” folder, then open the “Utilities” folder, and select “Disk Utility.”

2. Select the Startup Disk: On the left sidebar of Disk Utility, choose your startup disk or the disk where you want to install macOS Big Sur.

3. First Aid: Click on the “First Aid” button located in the toolbar or select “File” > “First Aid.” Disk Utility will verify the disk and check for errors, including file permissions.

4. Wait for Verification: Disk Utility will go through the process of verifying the disk and checking file permissions. This may take some time, depending on the size of your disk and the number of files involved.

5. Repair Disk Permissions: If Disk Utility finds any file permission issues, click on the “Repair Disk Permissions” button to fix them. Disk Utility will attempt to reset the permissions for the affected files to their default state.

6. Check for Further Issues: Once the repair process is complete, Disk Utility may display any additional issues that were detected and whether they were successfully repaired. Make sure to review this information to ensure that all problems have been addressed.

7. Restart Your Mac: After repairing file permissions, restart your Mac and attempt to install macOS Big Sur again. The repair process should help resolve any file permission-related problems encountered during the installation.

Keep in mind that repairing file permissions is most effective in older versions of macOS, and newer versions handle permissions differently. However, it is still worth performing this step as a troubleshooting measure, especially if you’re encountering installation issues related to file permissions.

If you continue to experience difficulties with the installation of macOS Big Sur, it is recommended to seek further assistance from Apple Support or visit an Apple Store for expert guidance.

Updating Existing Apps and Drivers

Before installing macOS Big Sur, it is important to update your existing apps and drivers to ensure compatibility and optimal performance with the new operating system. Outdated software and drivers can cause conflicts and issues during the installation process. Here’s how to update your apps and drivers:

1. Update Apps:

  • Visit the Mac App Store: Open the Mac App Store and click on the “Updates” tab to check for available updates for your installed apps.
  • Update Individual Apps: Click on the “Update” button next to each app that has an available update. Alternatively, you can click on the “Update All” button to update all apps simultaneously.
  • Outside the App Store: Some apps may not be available on the Mac App Store. For those apps, check the developer’s website or use built-in update mechanisms to download and install the latest versions.

2. Update Drivers:

  • Visit the Manufacturer’s Website: Identify the hardware components that require driver updates, such as graphics cards, printers, or external devices. Visit the manufacturer’s website for each component to check for available driver updates.
  • Download and Install Updates: Follow the instructions provided by the manufacturer to download and install the latest driver updates for your specific hardware components. Make sure to download the correct drivers that are compatible with macOS Big Sur.

By updating your apps and drivers, you can ensure that they are optimized for macOS Big Sur and reduce the likelihood of incompatibilities or issues during the installation process. This step is crucial, as outdated software and drivers can lead to crashes, errors, and even system instability.

After updating your apps and drivers, it’s recommended to restart your Mac before proceeding with the installation of macOS Big Sur. Restarting helps ensure that any updated components are properly loaded and ready for the installation.

If you encounter any issues during the update process or are uncertain about updating specific apps or drivers, it’s recommended to contact the respective app developer or hardware manufacturer for support and guidance.

Disabling Third-Party Security Software

During the installation of macOS Big Sur, third-party security software could potentially interfere with the process and cause installation failures or other issues. Disabling or temporarily turning off your third-party security software can help ensure a smoother installation. Here’s how to disable third-party security software:

1. Identify Installed Security Software:

  • Make a list of the third-party security software installed on your Mac. This may include antivirus software, firewall software, or any other security tools you have installed.
  • Note down the names of the software and the respective developers or providers.

2. Refer to Documentation or Support:

  • Consult the documentation or visit the support websites of each security software to understand how to temporarily disable or turn off the protection.
  • Look for the specific instructions related to disabling or pausing the software’s features or services.

3. Disable or Turn Off the Software:

  • Follow the instructions provided by the security software to disable or turn off its protection features. This may involve navigating through the software’s user interface or accessing specific settings.
  • Disable any real-time scanning, firewall, or other active protection features that could potentially interfere with the installation process.

4. Confirm Disabling:

  • Once you have disabled the third-party security software, verify its status to ensure it is successfully turned off.
  • Some security software may display an indicator or provide a confirmation message indicating that the protection features have been disabled.

5. Enable the Software After Installation:

  • After you have successfully installed macOS Big Sur, re-enable the third-party security software by following the same instructions you used to disable it.
  • Ensure that you update the security software to the latest version compatible with macOS Big Sur to maintain optimal protection.

Remember that disabling third-party security software temporarily leaves your Mac potentially vulnerable to security threats. Ensure that you reinstall or enable the security software promptly after the macOS Big Sur installation is complete.

If you encounter any issues or need further assistance with disabling or re-enabling specific security software, refer to the support resources provided by the respective software developers or consult their customer support for guidance.

Performing a Clean Installation of macOS Big Sur

If you’re experiencing persistent issues with your current macOS installation or prefer a fresh start, a clean installation of macOS Big Sur may be the recommended approach. This process involves erasing your current system and performing a fresh installation of macOS. Here’s how to perform a clean installation:

1. Backup Your Data:

  • Before proceeding with a clean installation, it is crucial to back up all your important data to prevent any loss. Use Time Machine or another backup method to create a complete backup of your files.
  • Ensure that your backup is verified and secure before proceeding to the next steps.

2. Create macOS Big Sur Installer:

  • Download the macOS Big Sur installer from the App Store. It will be saved to the /Applications folder as “Install macOS Big Sur.”
  • Connect a USB flash drive with at least 16GB of free space to your Mac.
  • Open the Terminal application (found in /Applications/Utilities) and enter the command: sudo /Applications/Install\ macOS\ Big\ --volume /Volumes/Untitled (replace “/Volumes/Untitled” with the appropriate name of your USB flash drive).
  • Follow the prompts and enter your administrator password when requested.

3. Erase the Startup Disk:

  • Restart your Mac and hold down the Command (⌘) and R keys simultaneously until the Apple logo or spinning globe appears.
  • When the macOS Utilities window appears, select “Disk Utility” and click “Continue.”
  • In Disk Utility, select the startup disk and choose the “Erase” tab.
  • Provide a name for the disk (e.g., “Macintosh HD”) and select the appropriate format (e.g., APFS or Mac OS Extended).
  • Click “Erase” to erase your startup disk.

4. Install macOS Big Sur:

  • Close Disk Utility and select “Install macOS” from the macOS Utilities window.
  • Follow the prompts to install macOS Big Sur. Select your newly erased startup disk as the destination for the installation.
  • Wait for the installation process to complete. This may take some time, so be patient.

5. Restore Data from Backup:

  • After the installation is complete, your Mac will restart. Follow the on-screen instructions to set up macOS Big Sur.
  • During the setup process, you’ll have the option to restore your data from the backup you created earlier. Use Time Machine or the appropriate backup method to restore your files and settings.
  • Follow the prompts to complete the restoration process.

A clean installation of macOS Big Sur can provide a fresh start and resolve persistent issues. However, it is important to note that performing a clean installation will erase all data on your startup disk, so ensure that you have a complete backup before proceeding. Also, be aware that reinstalling your apps and reconfiguring your settings will be necessary after the clean installation.

If you need further assistance or encounter any difficulties during the clean installation process, consult Apple Support or visit the Apple Support Communities for guidance.

Contacting Apple Support or Visiting an Apple Store

If you have exhausted all troubleshooting methods and still face issues during the installation of macOS Big Sur, or if you encounter any other technical problems with your Mac, contacting Apple Support or visiting an Apple Store can provide expert assistance and guidance. Here are the steps to reach out to Apple for support:

1. Apple Support Website:

  • Visit the official Apple Support website by going to
  • Search for your specific issue or problem using keywords related to your situation. Apple’s support website contains a vast array of articles, guides, and troubleshooting resources covering various topics and products.
  • Review the provided resources and follow any applicable instructions to resolve your issue.

2. Contact Apple Support:

  • If you are unable to find a solution on the Apple Support website, you can proceed to contact Apple Support directly for personalized assistance.
  • On the Apple Support website, select the appropriate product, category, and region to access contact options.
  • Options may include phone support, live chat, email assistance, or scheduling a callback with an Apple representative.
  • Choose the contact option that is most convenient for you, and provide the necessary details to initiate the support request.

3. Apple Store Visit:

  • If you prefer face-to-face assistance or your issue requires hands-on service, schedule an appointment or visit an Apple Store.
  • Go to the Apple Retail website to find the nearest Apple Store or schedule an appointment in advance.
  • Describe your issue when making the appointment to ensure that the appropriate Apple representative is available to assist you.
  • Arrive at the Apple Store at the scheduled time and check-in with an Apple employee to receive the necessary assistance.

Apple Support and Apple Store representatives are knowledgeable and experienced in diagnosing and resolving Mac-related issues, including installation problems with macOS Big Sur. They can guide you through the troubleshooting process, provide recommendations, and offer solutions tailored to your specific situation.

Remember to provide as much information as possible about your issue when contacting Apple Support or visiting an Apple Store. Describe the problem, any error messages encountered, and the steps you have already taken to troubleshoot. This information will help the experts better understand and address your concerns efficiently.

Whether you choose to contact Apple Support online or visit an Apple Store in person, reaching out to them ensures that you receive the support you need to resolve any technical issues you may be facing.