How to Downgrade macOS Sierra & Revert to El Capitan

For the vast majority of Mac users, macOS Sierra is a nice upgrade that goes without a hitch. For a small number of users, macOS Sierra presents a unique variety of problemsthat are impervious to all troubleshooting attempts, even reinstalling Sierra or a clean install. If you fall into the latter camp, or just decide that macOS Sierra just isn’t working out for you, you can downgrade from macOS Sierra to OS X El Capitan or Mavericks by using a Time Machine backup made beforehand.

This obviously requires a functioning Time Machine backup to work, one of of many reasons why setting up Time Machine on a sufficiently large external drive is one of the most important maintenance routines you can have on a Mac. The ability to prevent data loss, or roll back problematic software updates or OS upgrades is invaluable. 

Requirements to downgrade from macOS Sierra to prior Mac OS X

• Time Machine backup made prior to updating to macOS Sierra (either with Mac OS X El Capitan, Mavericks, Yosemite, or otherwise)
• A manual backup (separate from Time Machine) of any interim documents or data created between the time of the Time Machine backup and now*

* Remember, a side effect of rolling back with Time Machine is that any interim data will be missing unless you manually back up the files yourself before beginning the process (for example, if you restored from January 1 but it’s now January 15, you would lose files created or modified between those two dates unless you manually back them up before the restore). I personally get around this by creating a folder on the Time Machine volume and manually dragging and dropping important new documents into it, then just copy them back over to the restored Mac, but some users rely on iCloud Drive, DropBox, or other services. If you skip that, you’ll lose the interim data. 

How to Downgrade from macOS Sierra with Time Machine

1. Connect the Time Machine volume to the Mac
2. Reboot the Mac and hold down Command+R keys together to boot into Recovery Mode
3. At the “macOS Utilities” screen, choose “Restore From Time Machine Backup” and then click Continue
4. At the “Select a Backup Source” screen, choose your Time machine backup drive
5. At “Select a Backup”, navigate through the backups listed by date, time, and Mac OS version, choosing the most recent date with “10.11.6” (or whatever your prior Mac OS X release was) and click on Continue
6. At “Select a Destination”, choose the destination Mac drive to restore to, typically this is “Macintosh HD” then click on “Restore”
   • Optional: if FileVault is enabled, click on “Unlock” and authenticate to disable FileVault encryption before you can use the Restore function
7. Confirm that you wish to erase the target drive (“Macintosh HD” or otherwise) and restore it from the chosen Time Machine backup – this is irreversible, the drive will be formatted and erased and restored from the backup – click on “Continue”
8. Let the “Restoring” process complete, this can take anywhere from 30 minutes to several hours, depending on the size of the hard disk, the size of the backup, the speed of the computer, and the speed of the backup drive

Once the Mac has finished restoring from Time Machine, the prior version of Mac OS will automatically boot with all of the data backed up from that time period. 

In this example, that means the Mac is now back on MacOS X El Capitan 10.11.6, and macOS Sierra 10.12 is entirely removed from the Mac as the restore process effectively rolled back the Mac to before Sierra was installed. In case it wasn’t obvious, that is why Time Machine is called Time Machine, by the way, since it effectively lets a user step their OS and files back in time if need be.

Notes on Downgrading from macOS Sierra

Interim Files: Once the downgrade has complete and you’re back to El Capitan, Mavericks, etc, you’ll likely want to manually copy back over any of the interim files you saved from Sierra. If you skip this, you’ll simply be missing documents from the period of time where the El Capitan/Mavericks backup was made and when you installed Sierra. 

Re-Arming FileVault: If you used FileVault encryption, you had to disable it in order to restore from the Time Machine backup. FileVault will stay disabled after the restore is complete. This means you will need to enable FileVault on the Mac again after the downgrade has completed. Just do this through the System Preferences > Security control panel, and remember it requires a minor setup process and reboot as the drive encrypts itself.

Avoiding Potential Trouble with Safari 10 / WebKit?: If you are downgrading from macOS Sierra for troubleshooting purposes, specifically due to kernel errors, a billion com.apple.WebKit files open, or other persistent Safari and/or WebKit difficulty, you will likely want to avoid the Safari 10 update that will be available in the Mac App Store of El Capitan. If there is any bug with Safari 10 it will undoubtedly be fixed in a future software update, perhaps as Safari 10.0.1 or similar. To be clear, this is largely speculation based on personal extensive experience troubleshooting a highly problematic macOS Sierra setup, but a similar kernel file table is full issue has also been encountered by some users with El Capitan and Safari 10, suggesting a possible relationship.

What about MacOS Sierra 10.12.1? 10.12.2? 10.12.3, 10.12.x? For users who downgrade from the initial Sierra release for troubleshooting purposes, you’ll likely want to stay on the newly restored and stable release of Mac OS or Mac OS X for a while. When future macOS Sierra updates and bug fixes are released, perhaps as 10.12.1, 10.12.2, 10.12.5, or 10.12.x, it may be time to update to Sierra again. Some Mac users also like to stay on a specific stable release that works for them if they have no need for new features, a valid approach as well. 

Why downgrade macOS Sierra?

The vast majority of Mac users do not downgrade system software, and do not need to downgrade system software. With that said, for those individuals who choose to downgrade from a major system software release, they are typically doing so because of incompatibilities with required software, incompatibilities with third party apps or perhiphreals, or because of an overly problematic experience with the new OS release.

For me personally, I downgraded a specific MacBook Pro from macOS Sierra back to El Capitan because, despite significant troubleshooting efforts, clean installs, and re-installations of macOS Sierra, I could not get the Mac to maintain any degree of stability whatsoever with Sierra, and ultimately rebooting twice a day in between constant app crashes and freezes proved overly burdensome for my particular environment. It’s important to point out this type of experience is rare, and not at all what most people experience.

Is there a way to downgrade from macOS Sierra without Time Machine or without a backup?

Yes, but there are major caveats. Most of the time, it will lead to data loss. 

If you happen to have a USB installer drive from El Capitan or a prior release that is compatible with the Mac, you could format the Mac and perform a clean install of that Mac OS release. This will erase everything on the computer, including all files, data, photos, music, anything and everything. Losing all data is not acceptable to most users unless they make manual backups,.

Another method that would also result in data loss is using Internet Restore to reinstall Mac OS X, which downloads and attempts to reinstall the original version of Mac OS X which shipped on the Mac. 

Neither of these other approaches are going to be covered in this specific article, but you can learn how to clean install El Capitan here or clean install Mavericks here if interested.

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Did you downgrade from macOS Sierra using Time Machine? How did it go? Do you have any other tips or advice about downgrading macOS? Let us know in the comments below.

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