Some MacOS High Sierra 10.13.x users may wish to downgrade back to macOS Sierra 10.12.x or even Mac OS X El Capitan. Mac users can downgrade from High Sierra to a prior Mac OS release, either by formatting the hard drive and clean installing Sierra or another prior system release, or by relying on a Time Machine backup made prior to the update to macOS High Sierra.

The downgrade method we’ll cover here uses a Time Machine backup to restore to a prior version of macOS and downgrade macOS High Sierra 10.13. If you do not have a Time Machine backup made with a previous version of Mac OS, this will not be possible to follow.

Why downgrade from macOS High Sierra?

For most users, they should not downgrade from macOS High Sierra. Downgrading system software is probably most appropriate as a last resort or a final troubleshooting method, if some particular problem with High Sierra is making the Mac unusable or incompatible with your workflow. There are mixed reports of some Mac users updating to macOS High Sierra and then experiencing a range of problems, from rapid battery life draining, inability for some apps to open, apps crashing, strange performance problems or overall performance degradation, problems with mounting and reading disks, problems with networking connectivity and wi-fi, amongst other issues that could be considered deal breakers.

Important: Keep in mind there is no official downgrade path for macOS. Downgrading macOS High Sierra is accomplished by formatting the target hard drive, thereby erasing everything on it, then restoring from a prior Time Machine backup, or by formatting and then clean installing a prior version of macOS system software onto the computer, and then manually restoring files from some other backup. For our purposes here we will be covering a downgrade by erasing, then restoring from a Time Machine backup made prior to installing High Sierra.

If you do not have a Time Machine backup made prior to installing macOS High Sierra, of the Mac when on Sierra or El Capitan, then you can not proceed with this approach.

How to Downgrade macOS High Sierra to a Prior Mac OS Version

Backup your Mac before beginning this process, it requires erasing the hard drive and removing all data.

1. 1. Connect the Time Machine backup volume to the Mac if it’s not already attached
   2. Restart the Mac and immediately hold down Command + R keys together to boot into Recovery Mode on the Mac
   3. When the “macOS Utilities” screen appears choose “Disk Utility”
   4. Pull down the “View” menu in Disk Utility and choose “Show All Devices”
   5. Select the hard drive with MacOS High Sierra installed on it, then click the “Erase” button in the tool bar
   6. At the erase drive screen, name the drive and select “Mac OS Extended (Journaled)” as the file system format, click “Erase” when ready – ERASING DESTROYS ALL DATA ON THE SELECTED HARD DISK, DO NOT PROCEED WITHOUT A BACKUP
   7. When the drive finishes formatting, exit Disk Utility to return to “macOS Utilities” screen
   8. At “MacOS Utilities” select the option to “Restore from Time Machine Backup”

1. Select the Time Machine backup drive connected to the Mac as the backup source and choose to continue with the restore process
2. At the Time Machine “Select a Backup” screen, choose the most recently available backup that has the version of MacOS you want to restore (macOS Sierra is versioned as 10.12.x, Mac OS X El Capitan is 10.11.x) and select Continue
3. Choose the destination to restore the Time Machine backup to, this will be the hard drive you formatted earlier
4. Now choose “Restore” to confirm you want to restore the hard drive to the Time Machine backup

The restore of macOS will begin, this can take quite some time depending on the size of the backup, the speed of the hard drive, amongst other factors. Be prepared to wait a while, and let the entire process complete uninterrupted.

When the restore from Time Machine completes, the Mac will boot back up to the state and with the system version where the restored Time Machine backup was made.

Note that if the process of formatting the hard drive mentioned above is usually only necessary for Mac users who changed their file system to thew new AFPS file system available in macOS High Sierra. If the Mac file system was not changed then a regular old restore from Time Machine is possible without bothering with the additional step to format the drive, but nonetheless the data on the driven will be removed and replaced with the data on the Time Machine backup.