Updating to the latest version of MacOS doesn't have to be an all-or-nothing affair. You can install two different operating systems on your Mac and choose the one that suits you.

There are a few reasons why you might want to run two versions of the Mac operating system:

  • If you want to update your Mac to the latest software but you have legacy apps that may not run on it
  • If you are a developer and need to test your own apps on different versions of the MacOS 
  • If you want to try out a beta version of the Mac operating system

Here's how to set up your Mac so you can run two versions of the operating system on it:

  1. Back up your Mac
  2. Partition your hard drive
  3. Install the old version of Mac OS X in partiton 1
  4. Restore your Time Machine back up to that partition
  5. Install the new version of Mac OS X in partition 2

Back up your Mac

This is the first step because when you partition your Mac you will have to completely wipe it.

If wiping your Mac sounds like too much hassle to you, you could try installing MacOS on a external hard drive instead, we show you how here: How to run macOS from an external hard drive.

If you want to keep your current work, you need to create a backup of your Mac and ensure that it will fit on your smaller partitioned drive.

Partition your hard drive

You can partition the main hard drive into two separate drives and then install macOS Sierra on one and OS X 10.11 El Capitan on the other, for example.

We explain how to partition your Mac hard drive or SSD here.

Alternitively, create your partition by following these instructions:

  1. Boot Mac OS X into recovery mode (Hold down Option/Alt during startup)
  2. Use Disk Utility in recovery mode to wipe the main hard drive and split it into two partitions

Read about how to download MacOS here. We also have advice about downloading older versions of Mac OS X here.

Install the old version of Mac OS X in partition 1

  1. Use the Install option in Recovery to install OS X 10.11 El Capitan onto the main partition
  2. Recover your Time Machine backup into that partition

Install the new version of Mac OS X in partition 2

Follow the steps above to install the macOS Sierra, or the beta of the new version of MacOS onto the second partition.