How to do a clean install of Mac OS X

Want to install a fresh copy of Mac OS X on your Mac? Here's how to find, download and install a fresh copy of El Capitan, Yosemite or earlier versions of OS X

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  • OS X Yosemite Screen Clean install
  • how to clean install mac os x step 1 1333 Install file I
  • how to clean install mac os x step 2 800 Install file II
  • how to clean install mac os x step 3 800 Bootable USB disk I
  • how to clean install mac os x step 4 800 Bootable USB disk II
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How to do a clean install of Mac OS X

In this article we're going to show you how to perform a clean install of Mac OS X - we focus mainly on El Capitan and Yosemite, but approximately the same technique will work for earlier versions of OS X. This is often a handy option if your Mac is slow or otherwise misbehaving.

Before you start, remember to back up. Full instructions here: How to back up a Mac.

You'll need an 8GB or larger removable drive that hasn't got anything on it you need, and admin privileges.

We'll redownload the installer file for our chosen version of Mac OS X and store it on a removable drive: you'll need a USB flash drive with a capacity of at least 8GB. (We're going to erase it, so make sure it doesn't contain any valuable data.)

The drive you use needs to be formatted as a Mac OS Extended (Journaled) volume with a GUID Partition Table. To format the drive, go to Applications > Utilities and open Disk Utility. Select the drive and click Erase. (The name of the disk needs to be "Untitled", if the Terminal commands below are to work, so rename it if necessary.) Select Mac OS Extended (Journaled) as the format type. Click Erase.

Read next: How to install Yosemite and older version of Mac OS X

Next »

Next Prev OS X Yosemite Screen

In this article we're going to show you how to perform a clean install of Mac OS X - we focus mainly on El Capitan and Yosemite, but approximately the same technique will work for earlier versions of OS X. This is often a handy option if your Mac is slow or otherwise misbehaving.

Before you start, remember to back up. Full instructions here: How to back up a Mac.

You'll need an 8GB or larger removable drive that hasn't got anything on it you need, and admin privileges.

We'll redownload the installer file for our chosen version of Mac OS X and store it on a removable drive: you'll need a USB flash drive with a capacity of at least 8GB. (We're going to erase it, so make sure it doesn't contain any valuable data.)

The drive you use needs to be formatted as a Mac OS Extended (Journaled) volume with a GUID Partition Table. To format the drive, go to Applications > Utilities and open Disk Utility. Select the drive and click Erase. (The name of the disk needs to be "Untitled", if the Terminal commands below are to work, so rename it if necessary.) Select Mac OS Extended (Journaled) as the format type. Click Erase.

Read next: How to install Yosemite and older version of Mac OS X

 

Step 2 of 6: How to do a clean install of Mac OS X: Get the install file (El Capitan)

If you're reinstalling the latest version of OS X, our next step is easy: just go to the Mac App Store and search for its name. At time of writing, that means El Capitan. (For El Cap,we can save you a trip: just click here.) Hit Download.

Regardless of which version's installer you've download, you're likely to get a warning message at this point: 'Would you like to continue?' Click Continue, then enter your Apple ID and password. The installer is about 6GB, so downloading can take a while.

When it's finished downloading the installer will launch automatically, but we don't want to use it yet, so press Apple + Q (or rather Command + Q) to quit out of the installer. Find the installer file (which should have appeared in the Applications folder) and save it to an external flash drive.

 

Step 3 of 6: How to do a clean install of Mac OS X: Get the install file (Yosemite or earlier)

For older versions of OS X it's a bit harder to get the install file: Apple doesn't offer downloads of outdated OS versions through the normal store front, and searching for the name won't find what you're looking for. Instead, we'll use the Purchased section of the App Store. (This only works if you have installed the version before - it won't let you revert to an older version that you skipped.)

Make sure you're logged into the Mac App Store with the Apple ID you used to update to the version of OS X e're looking for, then click Purchased in the menu bar along the top. Scan down the list of apps you've purchased or download for free (which is in order of when you downloaded them) and find the name of your chosen version: Yosemite, Mavericks or whatever. Click download.

 

Step 4 of 6: How to do a clean install of Mac OS X: Create a bootable USB disk (part I)

Next we need to create a bootable USB disk so that we can install a new copy of OS X on the Mac from the flash drive. We've got full instructions on how to do that here - How to make a bootable Mac OS X install drive - but we'll run through the basics again. We're going to create the bootable drive using Terminal.

Connect the removable drive to your Mac, and make sure it's called Untitled - rename it if necessary. Make sure the installer (or at least a copy of it), called Install OS X El Capitan.app or similar, is in its default location in your main Applications folder (/Applications).

 

Step 5 of 6: How to do a clean install of Mac OS X: Create a bootable USB disk (part II)

Select the text of the following Terminal command and copy it (Command + C):

sudo /Applications/Install\ OS\ X\ El\ Capitan.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled --applicationpath /Applications/Install\ OS\ X\ El\ Capitan.app --nointeraction

Go to Applications > Utilities and double-click Terminal to launch it. Paste (Command + V) the copied command into Terminal and hit Return. Type your admin-level account password when prompted, and press Return again.

If you see the message 'To continue we need to erase the disk at /Volumes/Untitled. If you wish to continue type (Y) then press return', type Y and press Return; if not, don't worry. When the procedure is finished (it can take anywhere from a couple of minutes to half an hour), you'll see Copy Complete and Done.

 

Step 6 of 6: How to do a clean install of Mac OS X: Install from installer drive

Now we'll install a fresh copy of OS X from the installer drive.

With the boot drive connected, start up - or restart - your Mac while holding down the Option key (also known as Alt). This will take you to Startup Manager. Choose to install your chosen version of OS X from the drive. Select 'Disk Utility' and your hard drive, then Erase. Go back to the main menu and choose Install OS X.

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

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