This is how to perform a clean install of macOS Sierra. We’ll walk through how to create a bootable macOS Sierra installer on USB and why you may want to perform a clean install of macOS Sierra.
Apple changed the name of OS X to macOS this year. We’ll cover performing a clean install of macOS Sierra from OS X El Capitan, but it will also work if you are coming from an older version of OS X.
Many users will only need to upgrade to macOS Sierras, but if you suffer from a slow Mac on OS X El Capitan or you have a lot of files and apps that you want to wipe for a fresh start a clean install is a good idea.
macOS Sierra Clean Install vs Update
Performing a clean macOS Sierra install means wiping your Mac and starting over from scratch. Anything you don’t have backed up will disappear with no way to recover it on your own.
A normal macOS Sierra update installs right on top of OS X El Capitan and keeps all of your files and apps in place so that you don’t lose anything.
No matter which option you do, we recommend that you have a current Time Machine backup so that your data is safe.
What You Need to Perform a Clean macOS Sierra Install
Make sure that your Mac can run macOS Sierra and then you’ll need the following items.
- Download the macOS Sierra installer from the App Store.
- A 16GB Flash Drive that you can erase.
- USB C Adapter if you have a MacBook
- Time Machine Backup
You’ll need to download the macOS Sierra installer from the Mac App Store once it arrives on September 20th.
How to Make a macOS Sierra Installer on USB
Once you download the macOS Sierra installer do not proceed and install macOS Sierra. Instead you should close the file and proceed to create a bootable macOS Sierra install drive.
Make sure your USB drive is name “Untitled”. To do this Open Finder, right click on the USB drive name on the left and then choose Rename.
You can either make a bootable macOS Sierra installer USB drive with Terminal or with Install Disk Creator. The Install Disk Creator file is free and this is an easier option for most users.
To use Install Disk Creator, Open the app. If prompted allow the app to run.
Choose your USB drive that we just named Untitled. Click Select the OS X Installer and then choose the macOS Sierra Installer you just downloaded at the start of this guide. Now click Create Installer. If prompted enter your password. Wait while this completes.
You can also use Terminal to make a bootable macOS Sierra Installer. We recommend using the utility above unless you are experienced with Terminal.
You now have a bootable macOS Sierra installer on USB that you can use to perform a clean macOS Sierra install.
Perform a Clean macOS Sierra Install
Now that you are all prepared, it’s time to actually perform a clean install of macOS Sierra.
Plug your USB drive in to your Mac. Turn off your Mac. Now turn your Mac on and hold the Option/alt key.
Click on the Install macOS Sierra USB drive to the right of the screen. Click on the Up Arrow.
Now you will need delete your hard drive to perform a clean macOS Sierra installation. To do this choose Utilities -> Disk Utility from the menu bar.
Click on your hard drive, normally it is Macintosh HD. Click Erase and then make sure you choose Mac OS Extended (Journaled) as the format.
Name the hard drive, we recommend Macintosh HD. Then click Erase.
Once that completes you are ready to install macOS Sierra on your empty hard drive. You should see an installer screen with Continue at the bottom. Click on it and follow the on-screen prompts to finish your clean macOS Sierra installation.