When you’re ready to install macOS Mojave, you’ll need to choose between two different install methods. The default is an upgrade install, which will update the version of the Mac operating system currently on your startup drive to macOS Mojave, while retaining your user data, apps, and other assorted information you may have stored on your Mac.
The second option is a clean install. This method completely erases all of the data on the startup volume and replaces it with the macOS Mojave operating system. When the clean install is complete, you’ll have a pristine startup drive, reminiscent of when you first got your Mac.
We’re going to show you both install methods, although we’ve combined them, since most of the steps are the same.
Preparing for Mojave
Before you begin installing Mojave, there are a few things to do to ensure your Mac and you are ready for the new operating system. Start by reviewing these guides to make the process an easy one: Mac 101: How to Get Ready for macOS Mojave
And while it’s unlikely you’ll encounter any problems while installing, this Rocket Yard Guide may help you solve a problem, should one occur: Mac Installation Errors You May Encounter and How to Fix Them
The App Store
The macOS Mojave installer is available from the App Store. You can find instructions for downloading the installer, as well as information about which Macs are able to run Mojave, plus some tips on common problems and how to avoid them, in the Rocket Yard Guide: How to Download macOS Mojave and Avoid Common Problems
The above guide also contains information on creating a bootable macOS Mojave installer. You’ll need the bootable installer if you intend to perform a clean install on the startup disk. You won’t need a bootable installer if you’ll be performing a clean install on a non-startup disk.
Even if you don’t need the bootable installer, it’s a good idea to create one, as a way to archive the installer as well as to make installing macOS Mojave on multiple Macs an easier process.
At this point, you’ve acquired the macOS Mojave installer from the App Store, and are almost ready to perform a clean or upgrade install. Before you proceed, be sure you have an up-to-date backup of your Mac.
If you’re ready to begin the install, I’ve broken the process into two sections: an Upgrade Install and a Clean Install.
Clean Install Preparation
Performing a clean install on your startup disk requires a few extra steps, including starting up from the bootable installer you made earlier, and completely erasing your startup drive. It goes without saying, but I’m going to say it anyway:
Warning: This process will completely erase your startup drive, causing all data stored on the disk to be lost.
Insert the USB bootable flash drive you made earlier into your Mac, and make sure it successfully mounts.
Restart the Mac while holding down the Option key. Keep the Option key depressed until you see the boot manager appear, displaying icons for all the disks you can start up from.
Select the USB bootable flash drive from the icons, and then press the return key on the keyboard.
Your Mac will start from the bootable installer. The startup process can take a bit longer than usual, depending on how fast the USB device is. Eventually, you’ll see the macOS Utilities screen.
Select the Disk Utility option, then click or tap the Continue button.
Disk Utility will launch. Make sure you select the correct volume in the sidebar. If you’re performing a clean install, the usual name for the startup disk is Macintosh HD, though it may be different if you’ve customized the startup drive name, or are performing a clean install on a different volume. You can use the instructions in How to Use macOS Sierra Disk Utility to Partition, Erase Drives for erasing a drive.
When you’re finished with Disk Utility, select Quit Disk Utility from the Disk Utility window.
From the macOS Utility screen, select Install macOS, then click or tap the Continue button.
From here until the system setup process, the installer for upgrade or clean works the same.
If you’re performing an upgrade install, that is, installing macOS Mojave on top of an existing Mac operating system on your startup drive, you should be ready to begin.
Launch the macOS Mojave installer if it isn’t already running. You can find the installer in your Applications folder (/Applications), with the name Install macOS Mojave.
The Mojave installer will launch, presenting its welcome screen. Click or tap the Continue button.
The software license agreement will be displayed; scroll through it if you wish, and click or tap the Agree button.
A sheet will drop down, asking if you really agree. Click or tap the Agree button.
The installer will display the disk that Mojave will be installed on. The default will be your startup disk, which is the correct disk for a standard upgrade install. If you’re installing to a different disk, click the Show All Disks button (not visible on Macs with a single disk) and make sure you select the correct disk. If you intend to perform a clean install on a non-startup disk that contains no Mac operating system, you can do so by selecting the appropriate disk and continuing with these instructions. No matter what type of install you’re performing, upgrade or clean, once the disk is selected, click the Install button.
You may be asked to provide your administrator password, and to allow an install assistant to be added to your Mac. Provide your password, and then click the Add Helper button.
The installer will start copying files to your Mac, and present a progress bar. Once the initial files are copied, your Mac will restart to complete the installation process. After your Mac restarts, you’ll see the Apple logo and another progress bar. This second progress bar will include an estimate of the time remaining for the install. You can expect to wait anywhere from 30 minutes to an hour or more before the installation is complete. Your Mac will then restart and start the system setup process.
At this point, the installation (clean or upgrade) is complete, and the only task left to perform is to configure the new system. The number of tasks that need to be completed varies; those doing an upgrade install will only have a few screens to walk through before they’re ready to use their Mac, while a Clean install will have a lot more steps.
It’s not possible to give you complete step-by-step instructions because which steps will be present is determined both on the type of install you performed, and which version of the Mac OS you started off with.
With that in mind, here are the setup steps you could see. Remember, you may not see all of them, so don’t be concerned with the order you see them in, or if any are missing.
The Welcome screen will display a world map. Scroll through the list of countries and select your location, then click or tap the Continue button.
Select a keyboard layout that matches the style of keyboard you’re using; click or tap Continue when ready.
Data & Privacy is a new icon included with macOS Mojave; this screen displays a bit of background information about the new Data & Privacy system. Click or tap Continue when ready.
The Migration Assistant options will be displayed. You can select transferring data from a Mac, a Time Machine backup, or a startup disk, as well as moving data from a Windows PC. You can also choose not to transfer any data at this time. Remember, you can always use Migration Assistant to move data at a later date. Make your choice, and click Continue.
Sign in with your Apple ID; you can enter your Apple ID and password to associate this Mac with your Apple account. This will allow you to share photos, contacts, and documents between other devices associated with your Apple ID. Notice the use of the Data & Privacy icon on this screen. Make your selections, and click or tap Continue.
If you entered your Apple ID, you’ll be asked to supply your password. Click the Continue button when ready.
You can choose to enable or disable two-factor authentication. If you choose not to enable this security feature, you can enable it later with the Internet Accounts preference pane. Make your selection, and click Continue.
License terms will be displayed; when ready, click or tap the Agree button. A sheet will drop down asking you to verify that you have read the terms; click or tap the Agree button.
An administrator account will be created. Enter your full name and account name (Tip: Use an account name without spaces, such as your first initial and last name), a password, and a password hint. When you’re ready, click Continue.
Apple will offer to perform an Express Setup. This enables various options, such as Maps being allowed to determine your location, turns on Spotlight suggestions, and sends back anonymous analytics data to Apple. You can accept the express setup by clicking or tapping the Continue button, or select the Customize Setting Options to override the express setup. If you choose to customize, you’ll be able to enable or disable location services, set the time and time zone, and choose to send or not send analytics.
Finally, you’re given the option to select a look or theme for your Mac: Light, the standard look the Mac has had forever, or Dark, the new look included with Mojave. Make your selection, and then click or tap the Continue button.
The setup assistant will complete the configuration and then display your macOS Mojave desktop. Enjoy your new macOS.