Restore the Yosemite installation image to the USB flash drive: Launch the Finder and locate the “Install OS Yosemite.app” file. Right-click (hold the “control” key and click) on it and select “Show Package Contents”. Open Contents, then SharedSupport, and double-click on the InstallESD.dmg (disk image) file to mount it. If you open the new bootable drive in the Finder, you'll notice that it appears empty, other than the Install OS X Yosemite app. The boot files are hidden, and the installer app allows you to upgrade without booting from the drive if you don't need to.

Update: Go to Install macOS Sierra Using Bootable USB Flash Drive if you want to install macOS 10.12 Sierra instead.

Update 2: The instructions below will work to manually create a Mac OS X 10.11 El Capitan USB installation drive. I needed to upgrade my sister’s 2008 Macbook Pro and found that the existing Mac OS X 10.6 Snow Leopard did not support the “createinstallmedia” tool; I got a “Failed to start erase of disk due to error (-9999, 0)” error. I followed the instructions below to successfully create a bootable installer for Mac OS X 10.11 El Capitan, which is the last version to support the 2008 Core 2 Duo Macbook Pro.

In this post, I will go over instructions on how to create a bootable USB flash drive containing the Mac OS X 10.10 Yosemite installer. These instructions will also work for Mac OS X 10.9 Mavericks (excluding a Yosemite-specific step) and differ significantly from the instructions for creating a Mac OS X 10.6 Snow Leopard installer. You will need an 8GB USB flash drive for Mac OS X Yosemite or Mavericks.

I tried several methods which failed to create a bootable USB flash drive before finding one that succeeded. The instructions I found that worked, using Disk Utility, were located at How to Make a Bootable OS X Mavericks USB Install Drive and How to Create a Bootable Install USB Drive of Mac OS X 10.10 Yosemite.

Download the Mac OS X 10.10 Yosemite

First, download the latest Mac OS X version, which is 10.10 Yosemite. It is the version currently available for download from the “App Store”. (If you want an earlier version like Mac OS X 10.9 Mavericks, you’ll need to get it from elsewhere.)

Launch “App Store” and search for “OS X Yosemite”. Download it. (It is 5.16GB in size.)

Note: If you run the Yosemite installer to upgrade your Mac, the downloaded installer file will be deleted automatically after the upgrade is completed. To keep that file, you will want to move it out of the Applications folder so it won’t be deleted after an upgrade. Launch the “Terminal” app and run this command to move the downloaded installer app to your user’s “Downloads” folder:

Create Bootable USB Flash Drive Installer

By default, the Finder will hide system files which we will need to see. Run these commands in the “Terminal” app to expose the hidden files:

Prepare the USB flash drive:

1. Plug in a USB flash drive of size 8GB or larger.
2. Launch the “Disk Utility” to format the USB Flash drive.
3. On the left-hand pane, select the USB drive (not the partition under it, if any).
4. Click on the “Erase” tab, select “Mac OS Extended (Journaled)” for “Format” and input a name like “Install Yosemite” (or anything because this name will be overwritten later).
5. Click the “Erase…” button at the bottom and then the “Erase” button in the popup dialog. This format operation should take less than a minute to complete.

Restore the Yosemite installation image to the USB flash drive:

1. Launch the Finder and locate the “Install OS Yosemite.app” file. Right-click (hold the “control” key and click) on it and select “Show Package Contents”.
2. Open Contents, then SharedSupport, and double-click on the InstallESD.dmg (disk image) file to mount it. A volume called “OS X Install ESD” will show up on the desktop and under DEVICES in the Finder.
3. In the “OS X Install ESD” volume, right-click on the “BaseSystem.dmg” file and select “Open” to mount it. (Double-click won’t perform any action because it is a hidden file.)
4. Use Disk Utility to clone the “BaseSystem.dmg” to the USB flash drive:
   1. Select the “BaseSystem.dmg” in the left-hand pane and click on the “Restore” tab. The “Source” field will be populated with “BaseSystem.dmg”.
   2. Drag the “Install Yosemite” partition under the USB flash drive to the “Destination” field.
   3. Click the Restore button and then the Erase button.
   4. The USB flash drive will be written with the contents of “BaseSystem.dmg” file. Depending on the speed of your USB flash drive, it may take several minutes or longer to complete this operation.
   5. Once complete, the “Install Yosemite” partition will be renamed to “OS X Base System”.
5. Use the Finder to navigate to the USB flash drive. You will see two “OS X Base System” volumes in the Finder’s left-hand pane. The USB flash drive is the last one.
6. Under the USB flash drive’s “OS X Base System” partition, open the “System/Installation” folder. You will see an alias file named “Packages”. Delete it because we will replace it with a “Packages” folder below.
7. Use a second Finder window to open the “OS X Install ESD” volume. (To open a second Finder window, you can use the Finder menu’s “File/New Finder Window” command.)
8. Copy the “Packages” folder from the “OS X Install ESD” volume to the USB flash drive’s “System/Installation” folder.
   
9. Required for Yosemite (not required for Mavericks): Copy the “BaseSystem.chunklist” and “BaseSystem.dmg” files from the “OS X Install ESD” volume to the USB flash drive’s root “/” folder. If you don’t do this, you will get an “undefined error 0” when attempting to install Yosemite.
10. The USB flash drive is now complete. You can use it to boot a Mac to install Mac OS X 10.10 Yosemite.
11. Unmount all the Yosemite installer volumes by ejecting them; you must eject “OS X Base System” before “OS X Install ESD”.

Re-configure the Finder to hide system files. Run these commands in the “Terminal” app:

Boot With USB Flash Drive

To boot a Mac with the USB flash drive:

1. Insert the USB flash drive.
2. While holding the “option/alt” key down, turn on the Mac to display the boot Startup Manager.
3. You should see one or two icons, one for the internal hard drive and/or another called “OS X Base System” for the USB flash drive. (The internal hard drive may not be visible if it does not have a bootable partition installed.)
   • Note: If you don’t see the USB flash drive’s “OS X Base System”, try removing and re-inserting the USB flash drive while viewing the Startup Manager screen. The USB flash drive should then appear after a few seconds.
4. Select the “OS X Base System” and hit the “return/enter” key to boot from the USB flash drive.

Hopefully, this post will help you to create your own bootable USB flash drive installer for Mac OS X 10.10 Yosemite or Mac OS X 10.9 Mavericks.

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.

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:

Os X Yosemite Download Apple

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.

Mac Os X Yosemite Download Usb Stick

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.

How to downgrade a Mac running later macOS versions

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 Yosemite Installer

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).

Os X Yosemite Download To Usb

Visit your local Apple Store to download older OS X version

Os X Yosemite Download Usb Boot

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.