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How to do a clean install of macOS Sierra

Sometimes it’s nice to do some thorough housecleaning on your Mac. This could mean doing a “clean install.” A clean install is a software installation in which any previous version — and all its files — are completely eradicated.

The alternative to a clean install is an upgrade, in which elements of a previous version remain. For example, when I did an upgrade of macOS Sierra on my Macs, elements of Mac OS X El Capitan remained. If I had done a clean install, those elements would be history.

If you decide to do a clean install on your Mac, back up all your important files in case something goes wrong. So if you want to do a clean install of macOS Sierra, first create a bootable drive of the operating system, then:

  • Make sure your Mac is online.
  • Click on the Apple icon ().
  • Choose Restart from the drop-down menu.
  • Hold down Command-R when you hear the startup chime — and keep holding ‘em until your Mac reboots.
  • Click on Disk Utility in the OS X Utilities selector.
  • Click Continue.
  • Select your Startup Disk.
  • Click on the Erase tab at the top of the window.    
  • When your Mac’s startup disk is formatted, return to the Utilities window and choose “Install macOS.”
  • Select your startup drive when asked where to install the OS.
  • Follow the onscreen prompts to complete the installation.
Dennis Sellers
the authorDennis Sellers
Dennis Sellers is the editor/publisher of Apple World Today. He’s been an “Apple journalist” since 1995 (starting with the first big Apple news site, MacCentral). He loves to read, run, play sports, and watch movies.