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Make sure you have Install OS X El Capitan.app in your Application Folder 2. Select 'On an external drive' on the main MCPF window. Then, choose the disk you want to install the El Capitan installer on. Click install and prompt your password. Boot the computer you want to install El Capitan on with 'alt' held and select. If you are on an earlier version of OS X, you can download and install El Capitan from directly the App Store. OS X El Capitan on Mac App Store. Alternatively, if you currently on a later version of macOS and want to downgrade to El Capitan for some reason, you can officially do so only if you have purchased it earlier.

FIX This Copy of the Install OS X El Capitan Application Can’t be Verified. If the issue is with your Computer or a Laptop you should try using Restoro which can scan the repositories and replace corrupt and missing files. This works in most cases, where the issue is originated due to a system corruption.
When finished, OS X El Capitan will boot into a brand new clean install, running through the initial OS X setup process on the Mac as if the Mac was brand new. No files, no data, nothing will be on the Mac except for what comes with OS X El Capitan, that is what a clean install is for.

On this page:

Reinstall El Capitan on a computer alreadyrunning it

Upgrade from previous versions to OS X 10.11 (El Capitan)

From the Apple menu, select App Store....
When the App Store opens, search for and download El Capitan. If you don't already have an Apple ID, you'll need to create one. You can monitor the download process in the 'Purchased' section of the App Store.
Once the download is complete, the installer should automatically open.
If it doesn't, or you don't want to complete the installation at this time, you can come back later and double-click Install OS X El Capitan in your Applications folder.
Within the installer, click Continue, agree to the license agreement, and then choose the disk where you want to install El Capitan.
After you begin the installation, your computer may need to restart more than once before finishing, and then you may be asked to enter basic information.
From the Apple menu, select App Store..., and then install any available updates.

Reinstall El Capitan on a computer already running it

To reinstall or recover El Capitan, you must have an active internet connection. If you are on campus at IU, UITS recommends the wired Ethernet network instead of wireless. However, if IUSecure is your only option, see Connect to an IU wireless network in macOS if booted from your Recovery HD.

Reinstall while keeping files, applications, and settings

Restart your computer, and immediately hold down command-r until the gray Apple logo appears.
If prompted, select your main language and then click the arrow.
Click Reinstall OS X, and then Continue. Follow the instructions on the screen, and then choose your hard disk. Click Install, and enter your Apple ID information if prompted.
When the installation is complete, select App Store... from the Apple menu, and install any available updates.

Reinstall while erasing everything on your computer

Restart your computer, and immediately hold down command-r until the gray Apple logo appears.
If you see a screen asking you to select your main language, choose it, and then click the arrow.
Click Disk Utility, and then Continue.
In Disk Utility:
1. Click your hard disk in the left column, and then click the Erase tab.
2. Next to 'Format:', make sure OS X Extended (Journaled) is selected. In the 'Name:' field, give your disk a name. Click Erase.
3. Once it's completed, quit Disk Utility.
Click Reinstall OS X, and then Continue:
1. Follow the instructions on the screen, and then choose your hard disk.
2. Click Install. If prompted, enter your Apple ID information.
3. Once the installation is complete, you'll be asked to enter basic information, and have the option to transfer data from another computer or backup.
From the Apple menu, select App Store, and then install any available updates.

So, you’ve decided to download an older version of Mac OS X. There are many reasons that could point you to this radical decision. To begin with, some of your apps may not be working properly (or simply crash) on newer operating systems. Also, you may have noticed your Mac’s performance went down right after the last update. Finally, if you want to run a parallel copy of Mac OS X on a virtual machine, you too will need a working installation file of an older Mac OS X. Further down we’ll explain where to get one and what problems you may face down the road.

A list of all Mac OS X versions

We’ll be repeatedly referring to these Apple OS versions below, so it’s good to know the basic macOS timeline.

Cheetah 10.0	Puma 10.1	Jaguar 10.2
Panther 10.3	Tiger 10.4	Leopard 10.5
Snow Leopard 10.6	Lion 10.7	Mountain Lion 10.8
Mavericks 10.9	Yosemite 10.10	El Capitan 10.11
Sierra 10.12	High Sierra 10.13	Mojave 10.14
Catalina 10.15

STEP 1. Prepare your Mac for installation

Given your Mac isn’t new and is filled with data, you will probably need enough free space on your Mac. This includes not just space for the OS itself but also space for other applications and your user data. One more argument is that the free space on your disk translates into virtual memory so your apps have “fuel” to operate on. The chart below tells you how much free space is needed.

Note, that it is recommended that you install OS on a clean drive. Next, you will need enough disk space available, for example, to create Recovery Partition. Here are some ideas to free up space on your drive:

Uninstall large unused apps
Empty Trash Bin and Downloads
Locate the biggest files on your computer:

Go to Finder > All My Files > Arrange by size
Then you can move your space hoggers onto an external drive or a cloud storage.
If you aren’t comfortable with cleaning the Mac manually, there are some nice automatic “room cleaners”. Our favorite is CleanMyMac as it’s most simple to use of all. It deletes system junk, old broken apps, and the rest of hidden junk on your drive.

Download CleanMyMac for OS 10.4 - 10.8 (free version)

Download CleanMyMac for OS 10.9 (free version)

Download CleanMyMac for OS 10.10 - 10.14 (free version)

STEP 2. Get a copy of Mac OS X download

Normally, it is assumed that updating OS is a one-way road. That’s why going back to a past Apple OS version is problematic. The main challenge is to download the OS installation file itself, because your Mac may already be running a newer version. If you succeed in downloading the OS installation, your next step is to create a bootable USB or DVD and then reinstall the OS on your computer.

How to download older Mac OS X versions via the App Store

If you once had purchased an old version of Mac OS X from the App Store, open it and go to the Purchased tab. There you’ll find all the installers you can download. However, it doesn’t always work that way. The purchased section lists only those operating systems that you had downloaded in the past. But here is the path to check it:

Click the App Store icon.
Click Purchases in the top menu.
Scroll down to find the preferred OS X version

Instal Os X El Capitan