How to Fix It When macOS Big Sur Installation Fails

Update correctly with these fixes

If you're trying to install macOS Big Sur onto your MacBook, Mac mini or iMac, and the installation process fails, this can be for a number of different reasons. While it's an irritating error, it doesn't have to be a permanent problem with a mixture of quick fixes and more involved processes able to fix the problem. Here's how to fix it when macOS Big Sur installation fails on your Mac system. 

Why Won't Big Sur Install on My Mac?

There are a number of different reasons why Big Sur might refuse to install on your Mac. Some of these issues are very quickly resolved while others can require a more complicated fix. Here's a look at reasons why Big Sur won't install on your Mac.

  • The Apple servers are down. To download Big Sur, you need to be able to contact the Apple servers. If they're down, you can't install Big Sur, no matter what you do on your end. Check the live status of the servers to check the issue isn't with Apple.
  • You don't have enough space on your computer. If you don't have enough storage space on your Mac, you can't download the new operating system until you free up room. Big Sur requires at least 15GB of space according to Apple but typically, you'll need far more than that.
  • Your internet connection is unreliable. If your internet connection drops midway through the download or installation process, the installation can fail. Use an Ethernet connection wherever possible.
  • Your Mac is out of date. If your Mac is too old to run Big Sur, it won't download the new operating system. Check your Mac is compatible with the operating system first before trying any other fixes.

Why Does the macOS Big Sur Update Fail?

If you've installed macOS Big Sur but it won't update any more, the fix can be very simple providing you know where to look. It's important to narrow down the reasons why a Big Sur update fails before moving onto more permanent fixes. Here are some of the reasons why it can happen.

  • You lack storage space. If your Mac lacks storage space, it's unable to update Big Sur, even if the update is relatively minor. Clear some hard drive space as a priority. 
  • The Apple servers are down. When a new update has been launched, many users flock to update immediately which can lead to the servers being overloaded. Try at an off-peak time or on a different day.
  • Restart your Mac. Sometimes, simply restarting your Mac resets the connection and you're able to install a stubborn update without an issue again.

How Do I Fix a Mac Installation Error? 

If you keep suffering Mac installation errors, there are numerous ways you can fix the problem. These vary from quick fixes to solutions that require a bit more effort, so we've arranged the solutions in order of difficulty. Here's how to fix most Mac installation errors.

  1. Reboot your Mac. Try rebooting your Mac to fix most common issues. It often fixes any issues with updates or new operating system installations. 

  2. Clear storage space. Even if it seems like you have sufficient storage space on your hard drive, you might not actually have it available. Delete all unnecessary files to free up more room.

  3. Update your current operating system. If you're trying to install Big Sur and it won't work, try updating your current operating system with the latest incremental patches. This often solves the bigger issues.

  4. Delete the Install Mac OS11 file. If macOS Big Sur has only partially downloaded before failing, look for the Install macOS 11 file on your hard drive, delete it then try downloading it again.

  5. Log out of the App Store and log back in. Logging back into the App Store can sometimes fix issues with Big Sur not downloading correctly. 

  6. Use Recovery Mode. Restart your Mac and hold down Control + R before clicking Disk Mode to restart your Mac in Recovery Mode, then try installing the updates from here.

  7. Use the Apple website. It's possible to go to the Apple website to download the latest macOS updates rather than rely on the operating system itself to update. Try this method if nothing else works. 

  • How do I upgrade to macOS Big Sur?

    First, make sure your device will work with Big Sur. Then, go to the Apple menu > System Preferences and click Software Update. If this is your first time installing Big Sur, select Upgrade Now, and then follow the prompts.

  • How do I upgrade to macOS Catalina?

    To upgrade to macOS Catalina, go to the Apple menu > System Preferences and click Software Update. If macOS Catalina is an option, click Update Now. Or, click the box next to Automatically keep my Mac up to date to have your computer download updates as they arrive in the App Store

Was this page helpful?