Did the latest Mac OS X upgrade turn your trusty old Mac into a central heating boiler? Not a problem. Boot the Mac from the Mac OS X Install CD and revert it back to an older version of Mac OS X. It’s a bludge. Oh, you lost your only copy of the CD? Er... Hold on a sec. *dial mobile* Hallo, ist da die Feuerwehr?

Apple rendered the practise of upgrading Mac OS X with antiquated technology obsolete. The introduction of the App Store—and the inevitable discontinuation of internal CD drives—made it easier for users to perform OS upgrades. Following Mac OS X 10,6 Snow Leopard, all OS upgrades can be downloaded from the App Store for free. Receipts of OS upgrades that have been downloaded are stored on users’ Apple accounts. This means these OS upgrades can be downloaded again anytime.

There is another way to revert back to an older version of Mac OS X: Internet Recovery Mode. Unfortunately, it only works on Macs that came with Mac OS X 10,7 Lion and later. Pressing and holding Shift Option Command R (⇧⌥⌘R) at startup will not work on older Macs that have been upgraded to the latest supported OS. Instead, older Macs will boot into non-Internet Recovery Mode, but it can only reinstall the OS that is already installed.

If you’ve been downloading Mac OS X upgrades from the App Store since day one, you can heave a sigh of relief. Thankfully, it is not an audacious task to create your own physical Mac OS X Install media.

What you will need:

  • Previous version(s) of Mac OS X on the App Store
  • Flash drive with a capacity of at least 8 GB

That’s it. Let’s get started resurrecting your Mac!

One of my employee accidentally upgraded my iMac, which came with Snow Leopard, to Mac OS X 10,12 Sierra. It couldn’t handle the surge in performance. I reverted it back to Lion. I recreated the process on my husband’s Mac Pro to pen this piece. No, the employee didn’t get sacked.

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Step 1 — Launch App Store from the Apple menu () or Applications folder. Click the Purchases button and search for the earliest version of Mac OS X (Lion in this case). Click the Install button to proceed with the download. The file size depends on the model of the computer, and it is at least 3 GB in size. Grab a cuppa, this can take a while. If the Install button is greyed out, the file is already on the hard drive, and proceed to the next step.

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Step 2 — Once the download is complete, the file is saved to the Applications folder. Quit App Store and open the folder or simply press ⇧⌘A. Search for a large file called Install Mac OS X Lion.

Step 3 — Right click the Install Mac OS X Lion file and select Show Package Contents. This will reveal a folder containing all files associated with the installer file.

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Step 4 — Open the Contents folder then open the SharedSupport folder. Buried deep in the folders is a disk image file called InstallESD.dmg. A disk image is a copy of the entire contents of a “mounted” volume within the hard drive.

Before proceeding to the next step: Choose New Finder Window from the File menu or simply press ⌘N. This will open a separate window so that the SharedSupport folder won’t go anywhere. In the new window, open the Utilities folder or simply press ⇧⌘U and launch Disk Utility.

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Step 5 — Place the SharedSupport folder over the Disk Utility window. Drag and drop the InstallESD.dmg disk image file into Disk Utility’s sidebar on the left under mounted volumes (hard drives, CD drives, etc.). If done correctly, InstallESD.dmg will appear there.

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Step 6 — Close the SharedSupport folder and return to Disk Utility. Select InstallESD.dmg in the sidebar and click the Open button in the toolbar at the top of the window. The process can take about five minutes. Feed your Tamagotchi pet and keep it some company.

Step 7 — Once the process is complete, the disk image’s volume is mounted in the Finder under the name of Mac OS X Install ESD. A new window displaying the volume’s contents will appear over the Disk Utility window. The window is not at all necessary and can be closed. Do not eject this volume, and return to Disk Utility. If done correctly, the newly mounted volume will appear under InstallESD.dmg in the sidebar as shown in the picture above.

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It is possible to create a bootable DVD, external hard drive or flash drive. However, recent Macs don’t have CD drives. External hard drives with existing data will need a new partition. Partitioning a hard drive creates a secondary storage for other uses. Flash drive are faster and easier. This guide will use a flash drive. It is critical to backup everything on the flash drive.

The next step is to check whether the flash drive is formatted with a GUID Partition Table. It is a disk architecture that is common to Intel-based computers. Not to worry, most, if not all, flash drives are formatted with it.

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Step 8 — Plug in the flash drive and select the drive—not the partition of the drive—in Disk Utility’s sidebar as shown in the picture above. Take a look at the Partition Map Scheme at the bottom. If it says GUID Partition Table, proceed to the next step.

Select Mac OS X Install ESD in Disk Utility’s sidebar. The volume should already be there in the Source field on the right. Otherwise, simply drag and drop it into the field and proceed to the next step.

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Step 9 — Without selecting the flash drive in Disk Utility’s sidebar, drag and drop it into the Destination field on the right. Either the drive or the partition of the drive can be used.

WARNING: The next step will erase the contents from the flash drive. Backup everything on it or use a different flash drive. 

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Step 10 — Double check to make sure the Mac OS X Install volume is in the Source field and the flash drive is in the Destination field. Click the Restore button and proceed with the erase.

Step 11 — Enter the admin user’s password if prompted.

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Step 12 — Depending on the computer and read and write speed of the flash drive, the restoration process can take about five minutes. Play with a chatter ring to stay focused.

Step 13 — Once the restoration process is complete, look for the flash drive in the list of mounted volumes. The name of the flash drive partition should already be renamed Mac OS X Install ESD.

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Step 14 — Like in Step 7, a new window displaying the volume’s contents will appear over the Disk Utility window. Only this time the window displays the contents of the flash drive. Again, it is not at all necessary and can be closed. Select the flash drive in Finder and choose Eject “Mac OS X Install ESD” from the File menu or simply press ⌘E. Eject the other similarly named volume from earlier if it is there.

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Step 15 — Return to Disk Utility and right click the InstallESD.dmg disk image in the sidebar and select Remove. This will remove the eyesore from the Disk Utility’s sidebar for future uses.

The bootable Mac OS X Install flash drive is now ready for use, ta-da!

Back up everything on the Mac you want to revert back to an older version of Mac OS X. Shut down the computer and plug in the flash drive. Turn on the Mac and wait for the startup chime then immediately press and hold the Option key (⌥). You will be given the option to choose a startup disk. Use the arrow keys to select the “Mac OS X Install” volume and press Return (⏎). The Mac will boot into an old Mac OS X installer.

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Other Tips:

  • It is recommended to use the 7-pass erase option when erasing the Macintosh HD partition of the startup disk. This will overwrite unused space 7 times to ensure there is no corrupt file to disrupt the Mac OS X installation. This will take hours. Perform the erase at night when it is cool.
  • If you have a wireless keyboard, it is recommended to shut down the Mac instead of restart. Turn on the Mac and watch for the green indicator light on the keyboard. Press and hold the Option key as soon as the light comes on. This may take several attempts to get through.
  • Be warned, apps and their files backed up from the latest version of Mac OS X may become incompatible with the version you are reverting your Mac back to. Check for compatibility before proceeding.
  • If you upgraded your Mac from Snow Leopard to the latest supported OS, you will need the Snow Leopard Install CD or the Recovery CD that came with your Mac, to perform the downgrade. If the CD drive on your Mac is broken, you can use another Mac to make a bootable Mac OS X install drive.
  • If you used Time Machine to backup your Mac, you can only revert back to Mac OS X 10,5 Leopard or later. Although Time Machine is not supported on Mac OS X 10,4 Tiger and earlier, you can manually transfer your backup.
  • If you baulked at such a worrisome solution, Amazon is your bestie. You can buy a Snow Leopard install CD or drop a fortune on a collector item: Apple Mac OS X Lion Install flash drive.
  • Despite Apple’s claim that older Macs meet the minimum system requirements for latest Mac OS X upgrades; it doesn’t mean they can handle the surge in performance. They can become very hot to the touch, which can damage internal components.