How to perform a clean install of macOS on your Mac

“We’re going to show you how to perform a clean install of macOS,” David Price writes for Macworld UK. “This is often a handy option if your Mac is slow or otherwise misbehaving.”

“We’ll start by showing how to do this for the latest version of macOS (macOS Sierra, at time of writing), before moving on to the far tricker business of installing a clean copy of El Capitan, Yosemite or some earlier version of OS X,” Price writes. “You’ll need an 8GB or larger removable USB flash drive to hold the installer file for our chosen version of macOS. (We’re going to erase it, so make sure it doesn’t contain any valuable data.) You will also need admin privileges.”

Price writes, “Once installation is complete, you can restoring apps and settings from a Time Machine backup, or download them again manually.”

Read more in the full article here.

MacDailyNews Take: There’s nothing as sublime as a Mac with a clean installation.


  1. After a clean install you have to change a lot of bad default settings like:
    “natural”- read backward- scrolling, SW firewall turned off, Dock on the bottom, open safe files after downloading, store personal data in keychain, allow pop up windows, Crapple Music, etc.

    Then do not forget to uncheck syncing of calendars, notes and contacts to third party social networks unless you want them shared on Facebook and other servers of dubious security. You might want to turn off location services for a laptop unless you like being stalked for advertising. You also might want to make sure a laptop does not connect to any network until after you have OKed it.

  2. I have a niggling feeling that articles like these are “under the radar” sabotage to reset all your safeguards you have added over time. There is NO GOOD reason to “clean install” Mac OS. I have not done this for years and Apple themselves say this is unnecessary. Mainly it is a psychological benefit.

      1. When Apple first started to offer software through the App Store there was a big uproar about not being able to download the software for a “clean Install”. You could just update the software. Later Apple relented and allowed a download to a external drive. Apple relented not because it was technically superior to allow a clean install but just to “subside the mental grief” everyone was going through by not being able to “clean install”. Since then I have been to Apple stores and they basically tell you at the Genius Bar that a “clean install” buys you nothing over a straight “update”.

        1. But Apple offers OS recovery via partition or internet boot and these let anyone do a relatively-clean install. Apple has invested resources in preserving the clean install capability and it doesn’t seem to be for the purpose of placating a small group of IT enthusiasts. If they were willing to deal with the widespread outcry from removing floppies, DVDs, ports, etc. I think they would be willing to deal with the complaints of a minority of people who want to wipe and reload computer OSs. I’ll agree that it is usually unnecessary to perform a clean install, especially as users rely increasingly on sandboxed App Store apps that are forced to behave. I am, however, unaware of Apple saying that there’s no good reason to do a clean install. I sure wish we didn’t have to do clean installs, but that just doesn’t seem to be the case.

    1. I question the intentions of Mac utilities more than I would question the motives of a clean installation procedure. Apple has nobody to blame but themselves if the default security settings are poor, and Apple is doubly to blame if there is no guide to assist the user to make the wisest security choices for his situation. That would be wise software design, something Apple used to care about before they decided they wanted to store all your data for you for a monthly fee.

      Being able to do a Clean Install is extremely important for many reasons besides just maintenance. When moving a machine to another employee, a different project, or repurposing it for home media serving or whatever, it’s not a bad idea to clean it up. The best way to do that is, ta da, a clean OS install. Too bad Apple doesn’t have a particularly good way to FULLY delete unneeded apps and files, duplicates, and preferences, etc. Apple’s Finder acts more and more like Windows with every passing year — tons of hidden stuff and huge associated files with no way to figure out their use or importance.

      Example: it takes a 3rd party app like Monolingual to remove the thousands of language files that are installed by default. Apple does such a poor job allowing the user to select the language(s) he actually wants to see, you can easily be wasting megabytes of disc space for no reason. Bad preference, bad app file management. Apple doesn’t seem to care.

  3. Be prepared to lose some apps and more. Migration from a Time Machine backup did not include my Pages 4.3 and some other important stuff which was /Library. So double check if all you need is still there afterwards.

  4. Sometimes (and with great reluctance) you have to do a clean install of the OS. I tried deleting all remnants of Sophos anti-virus software from my wife’s Macbook Pro and could’t get the system to reboot. I reinstalled the OS but to get rid of the Sophos junk I’ll have to wipe the drive and start from scratch. I’m not looking forward to the aftermath such as reinstalling her music and so forth.

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