How to Fix the MacOS "Installation Failed" Error

First, lets close the error window by clicking "Okay."

Next, double-check your Mac's storage. Sometimes installations won't complete if there isn't enough space for your MacOS installation.

Your Mac hard drive also needs to have enough storage for day-to-day functionality. That means that if you have 14 GB of space on your "Macintosh HD," and the upgrade is 13.5 GB, that isn't enough space to upgrade your Mac and maintain its functionality. Ideally, you want to have no less than 5 GB of free space on your Mac at all times, but the ideal amount of free space is roughly 10 percent of your storage capacity.

Check your Mac's storage:

1. Click the Apple Logo
2. Select "About This Mac"
3. Click "Storage"
4. Calculate the amount of space your hard drive has versus the size of the installation

If your Mac has plenty of storage, move on to the next step!

Ideally, you shouldn't have any apps open when you start a MacOS installation, but sometimes an app or two might be open and interrupting other processes. If you have any apps open, follow the steps below to close them! If you don't have any open apps, skip to the next step.

Close open apps:

1. Right-click the open app in your dock. If you have a trackpad, a two-finger click is the same as a right-click.
2. Then, click "Quit."

Repeat these steps for any open apps. You can always tell apps are open if they have a little dot below them in the dock.

Lastly, restart your Mac. To restart your Mac, try the steps below:

Restart your Mac:

1. Click the Apple Logo
2. Select "Restart"

After restarting your Mac you can easily restart your MacOS installation!