How to Clean Install MacOS Mojave

Oct 3, 2018 - 24 Comments

How to clean install macOS Mojave

Performing a clean install of MacOS Mojave may be desirable to some Mac users. A clean install means erasing all data on a hard drive, and then installing a fresh new installation of MacOS Mojave to that Mac. The idea is that a clean install starts fresh, sort of like how a new Mac comes when you first open the box, with no customization, no third party apps, no user accounts, no user data, preferences, settings, caches, no personal files or data, it’s basically just a new clean installation of MacOS Mojave, and nothing else.

While the vast majority of Mac users should simply prepare for and update to macOS Mojave as usual from a prior MacOS system software release, thereby preserving their apps, customizations, personal files, and all else, this walkthrough is intended for users who want to erase a Mac completely and start over fresh to perform a clean install of macOS Mojave 10.14.


To perform a clean install of MacOS Mojave on a Mac, you’ll need the following:

Remember, a clean install will erase everything on the Mac, including all personal files, photos, movies, apps, any customizations or settings, or anything else. A clean install starts new, with absolutely no personalization or your data on the computer. Thus it becomes critical that you have separately backed up your personal data and anything important to you, as failure to do so will result in permanent data loss.

How to Clean Install MacOS Mojave

Warning: This process will erase everything on the Mac, and then perform a new clean install of macOS Mojave only. No personal files, data, or apps will be preserved or included on the Mac, unless you restore that data separately.

Do not proceed without sufficient backups of your important data and computer.

  1. Complete a full Time Machine backup before starting this process. It’s recommended to have a Time Machine backup, in addition to any manual file backup of your personal data that you wish to keep. Be certain you have backed up any important files, personal data, pictures, etc – do not skip a full backup
  2. Connect the bootable macOS Mojave installer drive to the Mac via a USB port
  3. Reboot the Mac, then immediately start holding the OPTION key on the keyboard
  4. Hold OPTION key until you see a boot selection menu appear on screen, then choose the “Install macOS Mojave” drive (this is the bootable USB installer) from the choices
  5. At the “macOS Utilities” screen, select “Disk Utility”
  6. In Disk Utility, choose “Macintosh HD” (or whatever your Mac hard drive is named that you want to format and clean install Mojave onto), then select the “Erase” button
  7. Erase the Mac to clean install macOS Mojave

  8. Choose “Macintosh HD” as the drive name, then go to “Format” and select “Mac OS Extended (Journaled)” or APFS depending on which file system format you use, then choose “Erase” – WARNING: ALL DATA ON THE MAC WILL BE PERMANENTLY ERASED
  9. Once the drive has finished erasing and formatting, quit out of Disk Utility
  10. Back at the ‘macOS Utilities’ screen, now select “Install macOS” from the available options
  11. Clean install macOS Mojave

  12. At the “Install macOS Mojave” splash screen, choose “Continue” and then select “Macintosh HD” as the destination to install macOS Mojave, and then choose “Install” to begin the clean macOS installation process
  13. MacOS Mojave will install fresh on the otherwise empty drive and computer, let this process complete, when finished macOS Mojave will boot up as if it were a brand new Mac

When the Mac has finished installing macOS Mojave, the computer boots up into a fresh clean install of macOS Mojave as if it’s a new computer, thus you’ll go through the standard setup process as if it were a new Mac. There are no personal files, no personal data, no apps, nothing on the Mac except for macOS Mojave and what comes with it by default. Thus, it’s a “clean install”.

A clean install of macOS Mojave showing a fresh desktop

At this point, you’ll probably want to setup the Mac as new, and then go about manually re-downloading apps, utilities, and other stuff you use to the Mac, as well as manually restoring any of your important personal files and personal data to the computer. Or you can skip all of that and just use the Mac with a clean install of macOS Mojave as if it were a brand new computer, without restoring or copying any data back to it. That’s entirely up to you.

So that’s how you clean install macOS Mojave. If you have any questions, comments, or other methods for performing a fresh install of macOS Mojave, share with us in the comments below.

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Posted by: Paul Horowitz in Mac OS X, Tips & Tricks

24 Comments

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  1. The Old Coot says:

    Not for the faint of heart. I once did this and promptly wish I hadn’t since it took months to find all the serial numbers I need for software.

    • Paul says:

      Indeed this is really not a recommended approach for most, unless you’re transferring ownership of a computer or selling it and want the new owner to be able to set it up as new. But even then, you can format and reinstall from Recovery Mode too. The clean install is really for specific use cases.

      Setting up a Mac as new with a clean install is a big undertaking!

  2. Edward says:

    All of this is fine except currently 10.14 Mojave has major Time Machine problems that are preventing thousands of users (including me) from backing up successfully, so beware! For more info look in support communities thread(s) – my ID their is “namuang26”.
    We hope that 10.14.1 will fix all this, but so far no indication of that or even acknowledgement of the problems from Apple.

    • MSterling says:

      +Edward, Can you elaborate on the TM issues. I have two alternating TM Ext. HD’s that seem to be both functioning correctly. I have already moved up to 10.14.1 beta 2. But did not experience any issues on 10.14 GM.

    • Thaw Malin iii says:

      Please tell us which community threads to look under. Time Machine, Mojave, etc. I have not been able to upgrade my MacBook Pro late 2016 touch bar from High Sierra to Mojave. Even doing a clean install and then adding just my account from my TM backup throws Mojave into darkness… I have worked through 8, yes 8, Apple Advisors and no one seems to figure out what is wrong. Apple Care even replaced my Logic board, top case with battery, flex cable keyboard, and something called Mylar BMU eDP TCON cable and still nothing will get me into Mojave with my Time Machine backup, or with just my TM backup of my account… Thanks for helping.

      • int says:

        Try doing a clean install of MacOS Mojave onto the MBP, then when setting up do a data transfer using the Time Machine backup to bring your stuff over?

        It sounds like maybe something in your user account is corrupt or messed up

    • Thaw Malin iii says:

      Please tell us which community threads to look under. Time Machine, Mojave, etc.

  3. Pilgrim says:

    I usually use TM and Carbon Copy Cloner for backups. If anything went wrong, which would be best for restoring to the previous state? I was thinking it would be CCC, but I have not had to do it so I’m not sure.

    Thanks!

  4. Leonbakhan says:

    I only do Clean Installations on my MacBook pro early 2015 RD.
    And so far has had no issues with Time Machine backup after installing macOS Mojave 10.14. I use Samsung SSD for TM backup.
    The only thing is after doing clean install leave the MB for the night and do a first back up after clean install without installing anything else.

  5. leonbakhan says:

    I only do Clean Installations on my MacBook pro early 2015 RD.
    And so far has had no issues with Time Machine backup after installing macOS Mojave 10.14. I use Samsung SSD for TM backup.
    The only thing is after doing clean install leave the MB for the night and do a first back up after clean install without installing anything else.

  6. Cal516 says:

    How do you restore your mail & calendar data after a clean install?

    • Leonbakhan says:

      I use mail app on the OS itself and again relog in.
      The mail is in sync with icloud and I have to do nothing.
      Everything gets updated itself.

  7. Goateed Geek says:

    This tip may help some of you.
    1- Download SuperDuper. Trial version works fine.
    2- Make a Read Only Disk Image (.DMG File) of your current installation.
    3- Do a clean install of Mojave.
    4- Mount the .DMG image you made previously.
    5- In Utilities, run the Migration Wizard and select the mounted .DMG file to import from.
    6- Al apps, settings etc. will be copied over to the clean install!
    7- Enjoy.

    • Frank says:

      That’s a pretty cool approach! But by using Migration Wizard that way, do you not gather all the accumulated junk from the prior system that you’re trying to avoid by performing a clean install of macOS Mojave? I have used Migration Wizard Mac to Mac many times and it works pretty well to setup a new Mac but I always suspect it brings over stuff you wouldn’t want too (caches, temp files, junk plists, preferences, application support clutter and bloat, etc)

      Personally I just want the following when setting up a new Mac, in terms of what’s coming from the old Mac: same apps, same app configurations, same system config, all personal files and photos

      I rarely do a clean install unless a computer is really misbehaving. I do reinstall MacOS from time to time out of essential troubleshooting too.

      • Goateed Geek says:

        Migration Wizard allows you 4 options to choose from such as Documents only… As to caches etc. I doubt much of that is copied, however I use CCleaner once a week to clear out the caches, cookies etc.

        FWIW, I used the steps above on 3 Macs in the past week, and they all run flawlessly.

    • Leonbakhan says:

      But that is not a perfect clean install.
      I take the trouble of :
      1. Backing up on my TM.
      2. logging out From the apps from my mac Book before upgrading.
      3. Doing a clean install
      4. Re installing the Apps from App store.
      Though this is a tedious process but practically and technically this is the cleanest of the Clean Install.
      And I do upgrade my iPhone as well as the iPad Pro almost the way.
      (Just before upgrading factory resetting the device, upgrading and then reinstalling the apps.)

    • James Allison says:

      Problem with time Machine is it’s not bootable, a clone made with Carbon Copy Cloner is.

    • James Allison says:

      Problem with time Machine is it’s not bootable, a clone made with Carbon Copy Cloner is. I think CCC is far superior to Super Duper

  8. Kurt says:

    Probably I’m very naïve here, but I’d simply like to get rid of old, obsolete stuff belonging to apps I’ve deleted a long time ago. Is there something in-between, that doesn’t force me to re-install apps I’m using right now? I always know where my towel is, but passwords and things like that, that’s a different kettle of fish …

    • Dan says:

      There are a few ways of doing this. Various “cleaner” apps will do things like delete caches, orphaned preferences and Application Support files. I use AppCleaner and CleanMyMac. Or you can manually go through the ~/Library for each user and /Library to bin unneeded files. You need to understand what files the cleaner is presenting to you, or where to find them yourself. If you have installer pkgs for apps, then Pacifist will tell you the BoM, listing everything that pkg installs.
      But in the grand scheme, this really doesn’t matter. Prefs and support files won’t be called if the app no longer runs. All they do is take up space, and pref files are tiny, although support files can be substantial.

  9. leonbakhan says:

    if you want the best..
    something has to be sacrificed for it..😍
    Also for Apps keep your passwords safely somewhere so that at the time of reinstallation you get them right.

  10. Pilgrim says:

    I assume that this process will also completely erase and remove a Bootcamp partition that is part of the mac’s startup drive. What’s the best way to get the bootcamp partition back up and running after a clean install?

    • Dan says:

      Bootcamp shouldn’t be affected. You will see a second partition under the Macintosh HD one named BootCamp. Leave that one alone.

  11. onutoda says:

    Everything worked fine when I’ve tried a clean install on my mac mini with a Samsung screen. Until step 4! Then the screen turned black and I couldn’t see the macOS Utilities screen. Any suggestions?

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