There are a few reasons why you might want to download old versions of Mac OS X. Perhaps you are relying on software you have discovered doesn't work properly in the newest version. Maybe you are using software that requires Rosetta, Apple’s solution for translating PowerPC apps after the Intel transition, or maybe you just don't like the new version of MacOS that you have installed.

Another scenario is that you are a developer and you need to be running multiple versions of Mac OS X so that you can be sure that your software runs correctly on them. Either way, you have questions and we have answers. 

There are a number of reasons why you might need, or want, to install an old version of Mac OS X on your Mac. You may have discovered that software you use doesn't work in the latest version of MacOS. Or perhaps you just don't like the version of MacOS that you have installed.

Alternatively, you may be a developer who needs to run multiple versions of Mac OS X so that you can be sure that your software runs correctly on them.

In this article we will cover how to install old versions of Mac OS X. We have a separate article about how to download the old version of Mac OS X here, so if you are yet to get the version of Mac OS X you want pop over there for advice on how to get it...

Now you have downloaded the installer of the old version of OS X you need to install it on your Mac, but that won't be a straightforward process, we'll take you through some of scenarios you may encounter below.

How to install Mac OS X on a old Mac

If you are installing the old version of Mac OS X on an older Mac you shouldn't have too many difficulties.

However, because newer versions of macOS tend to drop support for older Macs, this might mean your older Macs  can’t support a newer versions of macOS. This is because the drivers for the hardware on your new Mac simply don’t exist in the old software, so it can't run.

We have an article about installing MacOS on an older Mac here.

If your Mac was released in 2012, for example, you can download any Mac OS X versions that were supported when that Mac launched, and any versions that have since launched and support that generation of Mac.

For a 2012 Mac, that list should include: Mountain Lion, Mavericks, Yosemite, El Capitan, and macOS Sierra. But you won't be able to download Lion, Snow Leopard or anything older than that. 

How to install Mac OS X if Mac is too new

If you need to run an older version of OS X - pre Snow Leopard - perhaps because you are a developer testing versions of an app on older operating systems, you will need to find an older Mac to run it on.

Perhaps not this old though...

How to download Mac OS X Mountain Lion, Snow Leopard and older Mac software: iMac G3

How to install an older Mac OS X if the version on your Mac is newer

If your Mac is running a newer version of the MacOS you won’t be able to install an older version on top of it. At least not in a simple way.

Here's the steps you need to take:

  1. Start by downloading the installer of the version of OS X that you require from the Mac App Store, you should find it in the Purchases section. Follow the instructions here.
  2. You'll use this installation file to create a bootable installer on an external storage device. This drive needs at least 12GB of space available. Read more about creating a bootable installer here.
  3. Next completely erase everything from your Mac, restoring it to factory settings.
  4. Now re-install the older version of the OS software using the installer you just saved to the external drive.
  5. Now recover your Mac using a Time Machine back up that predates the new macOS installation, assuming you have one.

We have more information about downgrading your version of the Mac operating system here.

These steps aren’t guaranteed to work as there are a number of reasons why you may not be able to install older software on a Mac. For example, if the Mac shipped with a newer version of the software installed than the one you are attempting to install.

A better solution might be to run the older version of Mac OS X from an external drive or in a partition. We’ll look at those options below.

How to run an older Mac OS X on a external drive

A great way to run an older version of Mac OS X is to do so via an external storage device.

We have an article about running Mac OS X from an external drive here. 

The version of Mac OS X that you want to run can be installed on the external drive. Then all you need to do is hold Option/Alt down when you start up your Mac you can choose to boot from that drive.

The article above explains how to install Mac OS X on the external drive using Terminal.

The benefit of this method is you don't need to wipe your Mac. The disadvantage is that teh older version of Mac OS X might run slowly if it's on a slow USB memory stick.

Another option is running the older version of OS X in a virtual machine like Parallels or VMware, we look at that next.

How to install an older Mac OS X in a virtual machine

Before we look at how to install a version of Mac OS X on a virtual machine we need to look at Apple’s end user license agreement. This is a legal mine field. Read about Apple's Terms and Conditions and the EULA here.

Since Mac OS X 10.7 versions of the Mac operating system are only licensed to be run in a virtual machine if the host Mac is running the same version. This means that installing an OS X 10.8 VM on a Mac running another version of OS X is a violation of the 10.8 software license agreement. The newest version of OS X that can legally be run in a virtual machine with a different OS X host is Snow Leopard (10.6).

The solution here is too run the server versions of the OS that you require, as long as you have the software license from Apple.

Despite this, VMware Fusion and Parallels do support OS X client as well as server versions.

Another thing to note is that Apple’s end user agreement does allow you to run the Mac OS on two virtual machines and on one computer, but these virtual machines cannot be used for business (unless you’re a registered Apple developer).

Also bear in mind - Macs cannot boot into an OS X version older than the one they shipped with when new, even if it’s on a virtual machine. If you want to run older versions of OS X on your Mac, you need to get an older Mac that can run them.

There are a number of software packages that make it possible to run multiple versions of the Mac OS (and even Windows) on your Mac. These include Parallels, VMware Fusion, Virtual Box. Find out which is best by reading: Parallels, VMware, VirtualBox and Boot Camp compared.

To install an older version of OS X on a Parallels VM download the installer of that version of the Mac OS, create a new VM on your Mac and install the old version of OS X on that VM.

To install an older version of OS X on a VMware Fusion VM the process is similar to that outlined above.

VirtualBox is free, where Parallels and VMware aren’t, but VirtualBox requires using Terminal commands to get OS X installed so it’s a bit more complicated.  

Apple’s Boot Camp also offers the ability to run Windows on a Mac, but you don’t need to run Apple’s Boot Camp to create a partition that will be used for another version of OS X. You can create a partition and install it there. We look at that option below.

Related to virtual machines, you can also run Windows and use Windows apps the same way, read: How to run Windows apps on a Mac and
How to install Windows on a Mac.

How to run an older version of Mac OS X in a partition

You can install as many client versions of OS X as you wish on your machine, you just need to create a separate partition for each version. You won’t be able to install a version of OS X that is older than the machine you are using though.

We look at how to run two versions of Mac OS X on separate partitions here.

For information about Apple's terms and conditions for using Mac OS X and MacOS read: Should you agree to Apple's terms and conditions