How to Perform a Clean Install of OS X Yosemite

OS X Yosemite is officially out and ready for the public. It’s the latest OS X version from Apple and it comes with a heap of new features, including an all new look and Handoff (which lets you go back and forth on your iPhone or iPad with certain tasks).

OS X Yosemite is available now in the Mac App Store for free.

While most users will be fine with the easy upgrade process that OS X has, some users prefer to start from scratch with a clean OS install whenever they’re upgrading to an all-new version. A fresh and clean install means your computer’s hard drive is completely erased and OS X Yosemite is installed to factory settings. This means that no apps are installed and no files are stored — just the default apps and files that come with OS X Yosemite.

Personally, I always do a clean install. There are just too many problems that could happen when simply just upgrading, and I have so many files that they could get disorganized and cause unnecessary slowdowns after I upgrade. Essentially, when you do a simple upgrade, the new OS gets installed, and then the installer picks up all the old files and dumps it on top of the newly installed OS, which could easily cause problems.


With that said, here’s how you can install a fresh copy of OS X Yosemite and start with a clean slate.

Be warned, though: Performing a clean install of OS X requires you to make a bootable install drive using a USB flash drive. You’ll be moving a lot of files around and dealing with Terminal. If this isn’t something you’re comfortable doing yourself, we’d suggest simply upgrading, or grabbing a friend who can help you perform a clean install.


First, you’ll want to make sure that OS X Yosemite is supported by your Mac. Some Macs as far back as 2007 support OS X Yosemite, but for a full list of supported Mac models, check out this list.

You’ll also want to back up everything before you begin the clean install. You can either use Time Machine to easily backup all of your files to an external hard drive, or you can manually pick and choose files that you want to keep, and then transfer them to an external hard drive or USB flash drive.

Next, download OS X Yosemite from the Mac App Store. It’ll download and save to the Applications folder automatically. Furthermore, after it’s finished downloading, it may automatically begin the install process. If this happens, just quickly cancel it.

Making the Bootable USB Drive

In order to install a clean and fresh copy of OS X Yosemite, you have to create a bootable install drive using either a DVD, USB flash drive or an external hard drive. For this tutorial, we’ll be using a USB flash drive, since not everyone has an optical drive on their Mac, and you most likely have a USB flash drive anyway. Just make sure it’s at least 8GB in size.


  1. Plug in your USB drive and open Disk Utility.
  2. Select the USB drive in the sidebar and click on the Erase tab.
  3. Select Mac OS Extended (Journaled) in the Format box and name it Untitled (It should already be named that).
  4. Click Erase and wait for the format to finish.
  5. When it’s done, close Disk Utility and open Terminal. Type in the following command and press Enter:

sudo /Applications/Install\ OS\ X\ --volume /Volumes/Untitled --applicationpath /Applications/Install\ OS\ X\ --nointeraction

This command will officially make the USB boot drive and it’ll take about 20 minutes to complete, give or take. While it’s doing its thing, don’t mess with Terminal or eject the flash drive. Once done, it’ll say Copy complete. Done.

Installing OS X Yosemite

Now that you have a bootable USB stick with OS X Yosemite on it, it’s time to install it. With the USB drive plugged in, reboot your Mac and hold down the Option/Alt key. This will bring up a menu where you’ll select an install drive. Choose the USB drive that you just made (usually called OS X Base System in this case and will be colored orange). Click on the arrow pointing upwards below the drive icon to get started.


Now, before you install OS X Yosemite, you’ll want to erase and reformat your hard drive, so at the Install OS X screen, go up to the menu bar at the top and click on Utilities > Disk Utility.


From there, follow these steps:

  • Click on your main hard drive in the left-hand sidebar.
  • Click on the Erase tab and make sure Mac OS Extended (Journaled) is selected in the Format field.
  • Give the hard drive a name. If you want to stick with the Mac naming convention, go with Macintosh HD.
  • Click Erase in the lower-right corner to begin the wiping process.


  • After that’s done, close out of Disk Utility, where you’ll be brought back to the Install OS X screen.
  • Click Continue to begin the OS X Yosemite installation process and follow the steps provided.
  • Enjoy OS X Yosemite!

This is a fairly complicated method for creating a bootable install drive, but we’re guessing that once OS X Yosemite has been out for a few months, there might be some third-party tools released that will make the bootable disk creation process a bit easier, similar to that of OS X Mountain Lion tools that easily created a USB install drive for you. For now, though, this seems to be the quickest way that works.