These advanced steps are primarily for system administrators and people who are familiar with the command line. You don't need a bootable installer to upgrade macOS or reinstall macOS, but it can be useful when you want to install it on multiple computers without having to download the installer each time.

To create bootable USB installer for Mac to Install Mac OS X El Capitan on Windows, on Mac or VirtualBox, you have to create bootable USB flash drive. Let’s get started on how to do it. First, you have to download TransMac software for Windows and install it on your computer. If you have a spare USB flash drive laying around, you should consider putting it to good use by creating a bootable installation drive for the OS X El Capitan Beta. Creating a bootable drive has many benefits and uses. For starters, it makes it easy to install a fresh copy of whatever operating system you have configured on the drive.

What you need to create a bootable installer

• A USB flash drive or other secondary volume formatted as Mac OS Extended, with at least 14 GB of available storage
• A downloaded installer for macOS Big Sur, Catalina, Mojave, High Sierra or El Capitan

Download macOS

• Download: macOS Big Sur, macOS Catalina, macOS Mojave or macOS High Sierra
  These will be downloaded to your Applications folder as an app called Install macOS [version name]. If the installer opens after download, quit it without continuing the installation. To get the correct installer, download from a Mac that is using macOS Sierra 10.12.5 or later, or El Capitan 10.11.6. For enterprise administrators, please download from Apple, not a locally hosted software update server.
• Download: OS X El Capitan
  This will be downloaded as a disk image called InstallMacOSX.dmg. On a Mac that is compatible with El Capitan, open the disk image and run the installer within, which has the name InstallMacOSX.pkg. It installs an app named Install OS X El Capitan into your Applications folder. You will create the bootable installer from this app, not from the disk image or .pkg installer.

Use the 'createinstallmedia' command in Terminal

1. Connect the USB flash drive or other volume that you're using for the bootable installer.
2. Open Terminal, which is in the Utilities folder of your Applications folder.
3. Type or paste one of the following commands in Terminal. These assume that the installer is in your Applications folder and MyVolume is the name of the USB flash drive or other volume you're using. If it has a different name, replace MyVolume in these commands with the name of your volume.

Big Sur:*

Catalina:*

Mojave:*

High Sierra:*

El Capitan:

* If your Mac is using macOS Sierra or earlier, include the --applicationpath argument and installer path, similar to the way this was done in the command for El Capitan.

After typing the command:

1. Press Return to enter the command.
2. When prompted, type your administrator password and press Return again. Terminal doesn't show any characters as you type your password.
3. When prompted, type Y to confirm that you want to erase the volume, then press Return. Terminal displays the progress as the volume is being erased.
4. After the volume has been erased, you may see an alert stating that Terminal would like to access files on a removable volume. Click OK to allow the copy to proceed.
5. When Terminal says it's finished, the volume will have the same name as the installer you downloaded, such as Install macOS Big Sur. You can now quit Terminal and eject the volume.
   

Use the bootable installer

Determine whether you're using a Mac with Apple silicon, then follow the appropriate steps:

Apple silicon

1. Plug the bootable installer into a Mac that is connected to the Internet and compatible with the version of macOS you're installing.
2. Turn on your Mac and continue to hold the power button until you see the startup options window, which shows your bootable volumes.
3. Select the volume containing the bootable installer, then click Continue.
4. When the macOS installer opens, follow the onscreen instructions.

Intel processor

1. Plug the bootable installer into a Mac that is connected to the Internet and compatible with the version of macOS you're installing.
2. Press and hold the Option (Alt) ⌥ key immediately after turning on or restarting your Mac.
3. Release the Option key when you see a dark screen displaying your bootable volumes.
4. Select the volume containing the bootable installer. Then click the up arrow or press Return.
   If you can't start up from the bootable installer, make sure the External Boot setting in Startup Security Utility has been set to allow booting from external media.
5. Choose your language, if prompted.
6. Select Install macOS (or Install OS X) from the Utilities window, then click Continue and follow the onscreen instructions.

Learn more

A bootable installer doesn't download macOS from the Internet, but it does require an Internet connection to get firmware and other information specific to the Mac model.

For information about the createinstallmedia command and the arguments you can use with it, make sure the macOS installer is in your Applications folder, then enter the appropriate path in Terminal:

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:

1. Click the App Store icon.
2. Click Purchases in the top menu.
3. Scroll down to find the preferred OS X version.
4. Click Download.

This method allows you to download Mavericks and Yosemite by logging with your Apple ID — only if you previously downloaded them from the Mac App Store.

Without App Store: Download Mac OS version as Apple Developer

If you are signed with an Apple Developer account, you can get access to products that are no longer listed on the App Store. If you desperately need a lower OS X version build, consider creating a new Developer account among other options. The membership cost is $99/year and provides a bunch of perks unavailable to ordinary users.

Nevertheless, keep in mind that if you visit developer.apple.com/downloads, you can only find 10.3-10.6 OS X operating systems there. Newer versions are not available because starting Mac OS X Snow Leopard 10.7, the App Store has become the only source of updating Apple OS versions.

Purchase an older version of Mac operating system

You can purchase a boxed or email version of past Mac OS X directly from Apple. Both will cost you around $20. For the reason of being rather antiquated, Snow Leopard and earlier Apple versions can only be installed from DVD.

Buy a boxed edition of Snow Leopard 10.6
Get an email copy of Lion 10.7
Get an email copy of Mountain Lion 10.8

The email edition comes with a special download code you can use for the Mac App Store. Note, that to install the Lion or Mountain Lion, your Mac needs to be running Snow Leopard so you can install the newer OS on top of it.

How to get macOS El Capitan download

If you are wondering if you can run El Capitan on an older Mac, rejoice as it’s possible too. But before your Mac can run El Capitan it has to be updated to OS X 10.6.8. So, here are main steps you should take:

1. Install Snow Leopard from install DVD.
2. Update to 10.6.8 using Software Update.
3. Download El Capitan here.

“I can’t download an old version of Mac OS X”

If you have a newer Mac, there is no physical option to install Mac OS versions older than your current Mac model. For instance, if your MacBook was released in 2014, don’t expect it to run any OS released prior of that time, because older Apple OS versions simply do not include hardware drivers for your Mac.

But as it often happens, workarounds are possible. There is still a chance to download the installation file if you have an access to a Mac (or virtual machine) running that operating system. For example, to get an installer for Lion, you may ask a friend who has Lion-operated Mac or, once again, set up a virtual machine running Lion. Then you will need to prepare an external drive to download the installation file using OS X Utilities.

After you’ve completed the download, the installer should launch automatically, but you can click Cancel and copy the file you need. Below is the detailed instruction how to do it.

STEP 3. Install older OS X onto an external drive

The following method allows you to download Mac OS X Lion, Mountain Lion, and Mavericks.

1. Start your Mac holding down Command + R.
2. Prepare a clean external drive (at least 10 GB of storage).
3. Within OS X Utilities, choose Reinstall OS X.
4. Select external drive as a source.
5. Enter your Apple ID.

Now the OS should start downloading automatically onto the external drive. After the download is complete, your Mac will prompt you to do a restart, but at this point, you should completely shut it down. Now that the installation file is “captured” onto your external drive, you can reinstall the OS, this time running the file on your Mac.

1. Boot your Mac from your standard drive.
2. Connect the external drive.
3. Go to external drive > OS X Install Data.

Locate InstallESD.dmg disk image file — this is the file you need to reinstall Lion OS X. The same steps are valid for Mountain Lion and Mavericks.

Download Os X El Capitan To Usb Adapter

How to downgrade a Mac running later macOS versions

El Capitan Direct Download

If your Mac runs macOS Sierra 10.12 or macOS High Sierra 10.13, it is possible to revert it to the previous system if you are not satisfied with the experience. You can do it either with Time Machine or by creating a bootable USB or external drive.
Instruction to downgrade from macOS Sierra

Instruction to downgrade from macOS High Sierra

Instruction to downgrade from macOS Mojave

Download Os X El Capitan To Usb Driver

Instruction to downgrade from macOS Catalina

Before you do it, the best advice is to back your Mac up so your most important files stay intact. In addition to that, it makes sense to clean up your Mac from old system junk files and application leftovers. The easiest way to do it is to run CleanMyMac X on your machine (download it for free here).

Download Os X El Capitan To Usb Windows 10

Visit your local Apple Store to download older OS X version

If none of the options to get older OS X worked, pay a visit to nearest local Apple Store. They should have image installations going back to OS Leopard and earlier. You can also ask their assistance to create a bootable USB drive with the installation file. So here you are. We hope this article has helped you to download an old version of Mac OS X. Below are a few more links you may find interesting.