Perform a Clean Install of OS X or macOS El Capitan

Complete the El Capitan install in a few easy steps

OS X (or macOS) El Capitan offers two installation methods. In this guide, we'll focus on the "clean install" method. It replaces the contents of a selected volume with a new, pristine version of El Capitan (10.11). That means it does not include any previous versions of the operating system, applications, or personal data that may have been present on the selected drive.

A clean install will erase all of the data on your startup drive, including user data, music, movies, and pictures. Make sure you have a current backup before proceeding.

Why Perform a Clean Install?

The clean install method is a good choice for testing a new OS on a dedicated drive or partition, or when you have been experiencing software related issues with your Mac that you have not been able to resolve. When the problems are severe enough, you may be willing to trade in your apps and data for the peace of mind of a clean slate.

Before proceeding, verify that your Mac is capable of running OS X (or macOS) El Capitan.

Back-Up Your Existing OS and User Data

By installing El Capitan on your current startup drive with the clean install method, you will erase everything on the drive. That includes OS X, your user data, and personal files.

Perform a clean install on a non-startup disk

No matter the method, you should have a current backup of the existing startup drive's contents. You can use Time Machine to perform this backup, or one of the many cloning apps, such as Carbon Copy Cloner, SuperDuper, or Mac Backup Guru. You can even use Disk Utility. Before proceeding with the installation, it's important to take the time to create a current backup.

It's a good idea to check the target drive for problems. Disk Utility can verify a disk, as well as perform minor repairs using the First Aid feature. When completed, return here to begin the installation process.

Types of Clean Installs

There are two types of clean installs you can perform: an install onto an empty volume, and an install on a startup volume.

Clean Install on Empty Volume

This involves installing El Capitan onto an empty volume, or at least one whose contents you don’t mind removing. The key point is that you're not targeting your current startup volume as the destination for the clean install.

This type of clean installation is easy because, since the startup drive isn't involved, you can perform the clean install while booted from the current startup drive. There's no special, custom-made startup environment needed. Just start up the installer and go.

Clean Install on Startup Volume

The second option, and perhaps the more common of the two, is to perform a clean install on the current startup drive. Because the clean install process erases the contents of the destination drive, it's obvious that you can't boot from the startup drive and then try to erase it. The result, if it were possible, would be a crashed Mac.

That’s why if you choose to clean install El Capitan on your startup drive, there's an extra set of steps involved: creating a bootable USB flash drive that contains the El Capitan installer, erasing the startup drive, and then starting the clean install process.

How to Perform a Clean Install of OS X (Or macOS) El Capitan

If you haven't yet downloaded a copy of El Capitan from the Mac App Store, do so now. Once the download completes, you can continue the clean install process.

If you've decided to perform the clean install on an empty volume, you can jump to the section titled, "Perform a Clean Install of OS X (or macOS) El Capitan."

How to Erase the Startup Volume

To perform a clean install of El Capitan on your Mac's current startup drive, you'll first need to create a bootable version of the El Capitan installer. Once you finish making the bootable USB flash drive, follow the steps below.

  1. Insert the USB flash drive containing the El Capitan installer into your Mac.

  2. Restart your Mac while holding down the option key.

  3. After a short delay, your Mac will display the OS X Startup Manager, which will display all of your bootable devices. This should include the bootable USB flash drive you just created. Use your Mac's arrow keys to select the OS X El Capitan installer on the USB flash drive, then press Enter or Return on your keyboard.

  4. Your Mac will start up from the USB flash drive that contains the installer. This can take some time, depending on the speed of the flash drive as well as the speed of your USB ports.

  5. Once the boot process finishes, your Mac will display the OS X utility window. Before we can clean install OS X El Capitan, we must first erase the current startup drive that holds the older version of OS X. Select the Disk Utility option, then select Continue.

  6. Disk Utility will start. OS X El Capitan’s version of Disk Utility looks a bit different than previous versions, but the process for erasing a volume is the same.

  7. In the left-hand sidebar, select the volume you wish to erase. This will likely be in the Internal category and be named "Macintosh HD," unless you renamed it at some point.

    OS X El Capitan Disk Utility screenshot
  8. Once you have the proper volume selected, select Erase from the top of the Disk Utility window.

  9. You'll be asked if you wish to erase the selected volume and given the opportunity to rename the volume. You can leave the name or enter a new one.

  10. Just below the volume name field is the format. Make sure OS X Extended (Journaled) is selected, then select Erase.

  11. Disk Utility will erase and format the selected drive. Once the process is complete, you can quit Disk Utility. You will be returned to the OS X utility window.

  12. In the OS X utility window, select Install OS X, then select Continue. The installer will start, although it may take a few moments.

Perform a Clean Install of OS X (Or macOS) El Capitan

If you chose to perform a clean install on your current startup drive, then you have erased your startup drive and started up the installer.

If you chose to perform a clean install on a new or empty volume (not your startup drive), then you're ready to start the installer, which you'll find in the /Applications folder. The file is labeled Install OS X El Capitan.

With that step performed, we have unified the two installation processes; going forward, all steps are the same for both clean install methods.

  1. In the Install OS X window, select Continue.

  2. The El Capitan license agreement will display. If you'd like, read through the terms and conditions, then select Agree.

  3. You'll be asked to confirm your agreement. Select Agree.

  4. The El Capitan installer will display the default target for the installation; this isn't always the correct target. If it is correct, select Install and skip ahead to Step 6; otherwise, select Show All Disks.

  5. Select the target disk for OS X El Capitan, then select Install.

  6. Enter your administrator password, then select OK.

  7. The installer will copy the needed files to the drive you selected and then restart.

  8. A progress bar will display; after a while, an estimate of the remaining time will display.

    Estimate to copy OS X El Capitan initial files
  9. Once all the files are installed, your Mac will restart and you'll be guided through the initial setup process.

How to Set up OS X (Or macOS) El Capitan

When the installation process is complete, your Mac will reboot, and the El Capitan setup assistant will automatically start. The assistant will help you through the process of configuring your Mac and OS.

  1. When the Welcome screen appears, select which country your Mac will be used in, then select Continue.

    OS X El Capitan Setup Welcome screen
  2. Select your keyboard layout, then select Continue.

  3. The Transfer Information to This Mac window will appear. Here you can choose to move existing data from a Mac, PC, or Time Machine backup to the clean install of El Capitan. Because you can do this at a later date using the Migration Assistant, select Don’t Transfer Any Information Now, then select Continue.

  4. Choose to enable Location Services or leave it off, then select Continue. A window will drop down asking you to confirm that you do not want to use Location Services. Select Don’t Use.

    Some apps, such as Find My Mac, require Location Services to be turned on. However, since you can enable this service from the System Preferences, it's not important that you enable it now.

  5. You'll now be asked to add your Apple ID and whether to allow your Mac to automatically sign into various services upon booting up. You can set the Apple ID sign in now, or do it later from System Preferences. Make your selection, then select Continue.

  6. If you chose to set up your Apple ID, a window will drop down asking if you wish to turn on Find My Mac. Once again, you can do this at a later date. Make your selection by selecting Allow or Not Now. If you chose not to set up your Apple ID, a window will drop down asking you to confirm that you don't want your Apple ID set to log you into various services. Select either Skip or Don’t Skip.

  7. The Terms and Conditions for using El Capitan and related services will display. Read through the terms, then select Agree. A window will display, asking you to confirm the agreement. Select Agree.

  8. The Create a Computer Account option will display. This is the administrator account, so be sure to note the username and password you selected. The window will look slightly different, depending on whether you chose to use your Apple ID or not. In the first case, you'll have the option to sign in to your Mac using your Apple ID. In this case, you only need to provide your full name and an account name.

    The account name will become the name for your Home folder, which will contain all of your user data. We recommend using a name with no spaces or special characters.

  9. If you decided not to use the Apple ID, or if you removed the checkmark from the Use My iCloud Account to Log In item, then you'll also see fields for entering a password and a password hint. Make your selections, then select Continue.

  10. Select your time zone by clicking on the world map, or choose the closest city from a list of major cities around the world, then select Continue.

  11. The Diagnostics and Usage window will ask if you wish to send information to Apple and its developers about problems that may occur with your Mac. The information is sent anonymously. You can choose to send information to Apple, just send data to app developers, send to both, or send to no one. Make your selection, then select Continue.

  12. The setup process is complete. After a few moments, you'll see the El Capitan desktop, which means you're ready to start exploring the clean installation of your new OS.