How to Fix Big Sur “Installation Failed” Error on Mac

Apple MacBook Pro

A lot of Apple users have been waiting for the public release of macOS Big Sur since it was announced during Apple’s Worldwide Developers Conference (WWDC) last June 22, 2020. Later on, Apple has made the beta version available to developers and members of the Apple Beta Software Program.

Finally, Apple has released macOS Big Sur to the public last November 12, 2020, and several Mac users were quick to upgrade to the latest version of Mac’s operating system (macOS 11). Upon opening their Macs, users were notified of the update available and they excitedly jumped to hit the Upgrade Now button.

However, a lot of Mac users reported experiencing the Big Sur “Installation Failed” error on Mac after the release. The instances were varying for most users, but most of them resulted in getting “Installation Failed” when updating to Big Sur. The affected users were left with either a rolled-back version of macOS or a bricked Mac.

Getting “Installation Failed” When Updating to Big Sur

The Big Sur “Installation Failed” error on Mac was caused by a lot of people downloading the update at the same time. Imagine hundreds of thousands of Mac users accessing the Apple servers to download the 12GB installation files for macOS Big Sur. That would definitely cripple any server.

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Apple must not have expected the demand for Big Sur, but it should have been part of their preparations for the launch. Users are not sure what exactly happened on Apple’s side, but Apple’s System Status website reflected the issue the server was having. Here’s what was posted on the website:

macOS Software Update – Issue
Today, 10:00 AM – ongoing
Some users are affected

Users may not be able to download macOS Software Updates on Mac computers. The issue is currently being investigated.

Because of this problem, a huge number of Mac users were not able to successfully install macOS Big Sur. In some cases, the download of the installation files took several hours, only for it to fail in the end. Some users were not even able to initiate the download while others were able to go through the installation process, only to be greeted by the Big Sur “Installation Failed” error on Mac. The most unlucky ones got their Mac bricked after the failed installation.

Although Apple has rectified the issue and the System Status website indicates that the problem has been resolved, there are still several Mac users who reported getting this error. Why is that so?

Causes of Big Sur “Installation Failed” Error on Mac

The first appearance of this error was mainly caused by the surge of Mac users updating their Macs at the same time. Since too many users are accessing the same resources, the Apple servers were not able to accommodate all requests, leading to installation failure. Either the installation files were not downloaded completely or the connection to the server has been cut off. Apple resolved the issue on its own, but a lot of users are still experiencing the same error.

In this case, the problem does not have anything to do with Apple’s servers since all issues have been addressed. If you’re getting the same error after Apple has resolved the issue, then the reasons behind your error must be something else. It is possible that macOS is reverting to the old installation files previously downloaded to your Mac.

It is also possible that your internet connection is not stable enough to allow you to successfully download the installation files. When the download gets interrupted, the files are either incomplete or corrupted. This can cause your upgrade to fail.

Whatever the reason is, upgrading to macOS Big Sur should not be as complicated as others make it to be. As long as your Mac is eligible for the upgrade and there’s no major issues with your macOS, then you should be able to upgrade just fine. But if, unfortunately, you encounter this error, below are the things you can do.

Before You Start

Upgrading to macOS Big Sur is a big task that might result in disaster. To prepare you Mac and minimize the chances of errors popping up, here are some things you can do befor installing the upgrade.

  • Remember to back up your files before you update to macOS 11. You can use Time Machine or other backup methods.
  • Plug in your MacBook pro into AC power, especially for a major update like this one.
  • Get connected to internet. Make sure you have a stable internet connection.
  • Deactivate any proxy or VPN you are using before downloading the update.
  • Remove third party ‘kext’ files that might cause issues during the upgrade.

What To Do About Big Sur “Installation Failed” Error on Mac

If you’re getting “Installation Failed” when updating to Big Sur, the first thing you need to do is check your Mac if it is eligible for the upgrade. Here are the macOS devices capable of running macOS 11:

  • MacBook: Early 2015 or newer
  • MacBook Air: Mid 2013 or newer
  • MacBook Pro: Late 2013 or newer
  • Mac Mini: Late 2014 or newer
  • iMac: Mid 2014 or newer
  • iMac Pro
  • Mac Pro: Late 2013 or newer
  • Developer Transition Kit (2020)

If you noticed, Big Sur has dropped support for most Macs released in 2012 and 2013. So if your Mac was released in this time range, then you’re better off sticking with Catalina.

But if you have a newer Mac that should be compatible with Big Sur and you’re getting this error, here are the solutions you can try:

Fix #1: Free Up Enough Storage Space.

Sometimes the upgrade fails to proceed if there is not enough space on your Mac. A clean installation of Big Sur requires 12.5 GB of free space, but you need to make room for other files. Ideally, you need to have 15-20 GB of free disk space for the upgrade to be completed successfully. However, there are users who reported getting errors even with more than 20 GB available storage. In this case, try to free up as much space as you can. You can use a Mac repair app to delete junk files and claim back precious storage. Once you have enough space, try running the upgrade again.

Fix #2: Reset SMC.

Apple recommends resetting the SMC before installing any update to prevent installation failure.

To do this:

  1. Shut down your Mac.
  2. Make sure your cable is plugged in.
  3. Hold Shift + Ctrl + Option + Power buttons for about 10 seconds.
  4. Click the power button and wait for your Mac to boot up.

After restarting, try installing Big Sur again.

Fix #3: Reset NVRAM or PRAM.

Another solution you can try is resetting your Mac’s NVRAM or PRAM. To do this:

  1. Shut down your Mac.
  2. Hold Option + Command + P + R buttons for about 20 seconds.
  3. Wait for your computer to restart.

After restarting, try installing Big Sur again.

Fix #4: Remove Old ‘Install macOS..’ Files.

If you have attempted installing Big Sur before, make sure to delete old installation files from the Applications folder. Your Mac might be calling upon these old installation files, causing the upgrade to fail.

Fix #5: Check the Date and Time.

If your system time and date are incorrect, it can get in the way of the upgrade. Double-check your Mac’s date and time by following the instructions below:

  1. Go to Apple menu > System Preferences > Date & Time.
  2. Tick off Set Date and Time Automatically.
  3. If the option is already checked, uncheck it then reboot your Mac.
  4. Go back to the Date and Time panel and check the option again.
  5. Next, try re-installing macOS Big Sur.

Fix #6: Do a Fresh Install.

If you still can’t install Big Sur successfully after following the steps above, you might need to do a fresh install. To do this:

  1. Shut down your Mac.
  2. Press Power + Command + R keys to open the macOS Utilities screen .
  3. Click Reinstall macOS.
  4. Select Disk Utility > Erase HDD.
  5. Install macOS Big Sur.

Wrapping Up

macOS Big Sur involves a major overhaul of the macOS operating system. Aside from new features, it also includes major changes in the UI and other aspects. But if the upgrade keeps failing, it would probably be better to wait until the latest macOS version becomes more stable before you upgrade.

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