[FIXED] The macOS Installation Couldn’t be Completed


By Jack Lin

Update on

The macOS Installation Couldn't be Completed
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I get a message saying that “the macOS installation couldn’t be completed” during an update.

Frankly, I am clueless about what has happened here. What I know is that the installation is not completed. In fact, I was trying to install an update on my MacBook Pro, but it did not succeed. Even after a restart, the same message appears, and I don’t know what to do.

I am more than happy if anyone can assist me and get this installation completed.

The above is an extract of a query posted by a MacBook Pro user. If you are reading this article because you experience the same, continue reading the solutions we offer below.

“The macOS installation couldn’t be completed” – What Does it Mean?

Before looking at the solutions to address this issue, let’s learn more about the issue itself. If you see the “the macOS installation couldn’t be completed” message, things can be pretty disturbing. This is particularly true if you are a novice user. Well, if you see such a message, it can be due to several reasons.

The macOS Installation Couldn't be Completed

Listed below are the possible reasons behind the “the macOS installation couldn’t be completed” message.

• The Installer of Your System is Corrupted

If the macOS installer is corrupted and you cannot complete the installation, you might see the above error message.  

• The Installation Process is Interrupted

Due to various reasons, your installation can be interrupted at some point or another. It can happen as a result of the files that are located on other mounted drives.

• The Disk You Try to Install the macOS is Malfunctioning

Sometimes, the disk on which you intend to install macOS can experience some errors. If that’s the case, failures on OS installation can be expected. Interestingly, it is among the most common reasons behind this error message.

• Lack of Space on the Disk

The other major reason behind this error message is the lack of free space. Just like in the previous case, a lack of disk space can prevent your OS from installing properly. As a macOS user, you should know that your disk should have at least 8GB of space.

Besides, click here to learn more about how to repair Windows 10 without CD and fix the iTunes backup now greyed out.

How to Fix The macOS Installation Couldn’t be Completed With Ease

#1 – Create a Backup of Your Data Before Starting the Process

Now, let’s move to the process of solving the “the macOS installation couldn’t be completed” error. As the first step, you are supposed to create a backup of the available data on the Mac.

This step is compulsory to avoid potential data losses due to some unfortunate incidents. The best approach is to save your data on an external device so you can retrieve them later on.

If you can start the Mac, as usual, you can copy all the important files to a USB drive. However, if you cannot start the Mac because of the installation error, follow the steps below.

In this case, you will have to create a bootable USB drive using a professional tool like Recoverit. And this tool can also fix the Lenovo stuck on the boot menu issue.

Steps to Prepare to Recover Data on a Mac

Below is the step-by-step guide to preparing your Mac for the data recovery process.

Before everything else, you are supposed to find another MacBook and have Wondershare Recoverit installed on it.

Start by Creating a Bootable Media

After launching the software, you should click on the option “Recover from Crashed Computer.” In this case, you should plug an empty USB drive into the new Mac. That will let you create a new bootable USB device.

Recoverit Data Recovery
Choose the Drive and Define a Format

Now that the USB drive is selected as the “Bootable Media Drive,” it will be formatted by Recoverit. This is to eliminate potential errors and gain maximum compatibility. You should be patient and wait for the process to be completed.

Choose the Drive and Define a Format
Boot the Faulty Mac using the Bootable USB

Now that you have done the groundwork. Let’s move to the booting process of the Mac. Just plug the bootable USB drive into the faulty Mac. Then, boot it from the USB drive.

Start the Data Recovery Process

Once the bootable device is connected to the Mac and booted with it, you can proceed to recover data. You can copy the files from your faulty Mac to the functioning hard drive. Select the hard drive and click on “Start Copy.”

Now, the software will take a couple of minutes and fetch data. Once the copying process is completed, you can see the message “Copy files completed.”

Boot the Faulty Mac using the Bootable USB

After saving all the files you want, you can fix the respective Mac on which the installation failed. You can use the methods mentioned below to fix your Mac and get it back in action.

Also, the message “your screen is being observed” on your Mac can stun you if you are a novice user. Here, let’s figure out the reasons and best solutions for that.

#2 – Restart the Mac and Try to Install the Update Again

In most cases, you can solve this issue simply with a restart. As you may already know, most of the minor glitches related to macOS can be fixed with a restart. To do this, you should choose the Apple menu at the top right.

Then, select the option called “Restart.” If not, you can even press and hold the power button and shut down the Mac. Then, you should turn it on.

Restart and Install Update again to fix The macOS Installation Couldn't be Completed

#3 – Use a Combo Installer to Finish the Installation

As mentioned before, the macOS installation couldn’t be completed due to a corrupted installer as well. If that’s the case with your Mac, use a combo installer and overcome it.

To do that, you should go to the support website of Apple and download their Combo installer. In fact, a Combo installer is a tool that can install your macOS updates more smoother.

Use a combo Intaller to fix The macOS Installation Couldn't be Completed

#4 – Boot Your macOS Computer in Safe Mode

The next solution is to boot the respective Mac in Safe Mode. Mentioned below is the guide you can use to boot the device in Safe Mode.

  • As the first step, you should restart the Mac.
  • Then, once the Mac is booting, press and hold the Shift key on its keyboard.
  • You can release the shift key once the Apple logo is displayed on the screen.
  • You can see the Safe Boot on your menu bar – choose it.

#5 – Use the First Aid Feature to Repair the Disk

“The macOS installation couldn’t be completed” message can appear due to a disk error as well. Faulty disks often cause various issues when installing updates and other programs.

However, the good news is that this error can be fixed using a built-in feature called First Aid (Fix the 0x80040610 error on Outlook with ease).

Below are the simple steps you should follow to repair the disk and make it work again.

  • First, go to Applications and choose Utilities.
  • Then choose Disk Utility.
  • Now, go to the startup disk on which the macOS is already installed.
  • Then, run the option called “First Aid.
Run First Aid to repair disk to fix The macOS Installation Couldn't be Completed

As a result of running this utility, scanning will take place. If everything is perfectly in place, you will get a notification. This step is particularly necessary if the installation is halted due to a disk error.

#6 – Get Rid of the Login Items That Aren’t Required

It is always possible to remove unwanted login items. Some of those items can hinder the smooth installation of updates. So, once those troublesome login items are removed, you may be able to install the updates.

Mentioned below is how to do it.

  • First, you should go to “System Preferences.”
  • Go to “Users & Groups” and choose “Current Users.”
  • Then, go to Login Items.

You can see the login items that are already activated on your system now. Get rid of the items that are no longer needed.

By the way, here are the top solutions for Microsoft Word that keeps crashing Mac issues for your reference.

#7 – Reset PRAM

As you may know, PRAM is responsible for holding various settings and configurations for your Mac.

For instance, it saves the screen’s brightness, volume, resolution, etc. If there is anything wrong with the PRAM, it may lead to installation problems.

So, if none of the options have worked so far, reset the PRAM. To do that, restart the Mac and use the Option” + “CMD” + “P” + “R keys. Once the Apple logo is displayed, you can release those buttons, and PRAM will be reset.

Reset PRAM to fix The macOS Installation Couldn't be Completed

#8 – Reinstall Your macOS using Recovery Mode

If none of the solutions have worked, the last resort is to reinstall the macOS. Just restart the device and hold the Option” + “CMD” + “R keys. Wait for a while so you can hear the startup sound and see the Apple logo. Then, go to Utility and choose “Reinstall macOS.”

Reinstall Your macOS using Recovery Mode


  1. Why does my macOS installation keep failing? macOS installations can fail due to various reasons, including insufficient disk space, incompatible hardware, or network issues.
  2. How much disk space is required for macOS installation? The disk space required for macOS installation varies depending on the version and additional software. It is recommended to have at least 20 GB of free space.
  3. Can I install macOS on any computer? No, macOS has specific hardware requirements, and not all computers are compatible with the operating system. Check the system requirements before attempting installation.
  4. What should I do if I encounter network errors during installation? If you encounter network errors, try restarting your router, checking your connections, and disabling any firewall or antivirus software temporarily.
  5. When should I consider seeking professional assistance? If you have followed the troubleshooting steps and still cannot complete the installation, it is advisable to contact Apple Support or an authorized service provider for further assistance.


While macOS installations are typically smooth, encountering issues that prevent completion is not uncommon. By understanding the common reasons for installation failures and following the appropriate troubleshooting steps, you can overcome these obstacles and successfully install macOS on your computer. Remember, if you find yourself unable to resolve the issue, do not hesitate to seek professional help.


10 years of experience in information and computer technology. Passionate about electronic devices, smartphones, computers, and modern technology.