Even though Mac High Sierra improved some great feature like better photo editing tool, speedier Safari, and smarter Notes, there may well be reasons why you want or need to go back to an older version of the Mac operating system. It could be that the many of your favorite apps are 32-bit and High Sierra does not support that; maybe you need to run an older version of macOS for testing; or perhaps, you just quite like macOS Sierra.

Unfortunately, uninstall High Sierra or downgrading to an old version of macOS is not that simple as think: first uninstall High Sierra and then reinstall macOS Sierra. The rule is that once you click, install and run High Sierra, it won’t allow you to downgrade it that way. But it is still possible to downgrade your Mac with the steps below.

Step 1 Clean up your Mac’s drive

Sounds irrelative? Here’s the reason. Compared to macOS High Sierra, the regular macOS Sierra requires more space on the drive to operate, thus you should clean your Mac to leave more space. You can:

1. Uninstall the apps you don’t use. Go to Applications and delete the one you barely use.

2. Clean browsing cache.

3. Clean up large attachment files in Mac Mail

4. Manage your storage. Click About my Mac on the left top of the screen. Click Storage->Manage, then you can see everything that takes your big Mac space and remove it. In this case, I would delete this video.

Step 2 Backup your Mac

The downgrade process will erase everything that you work on Mac High Sierra from your hard drive entirely. You could use an external hard drive or cloud backup like Google Drive, iCloud to back up a copy of it. Also, backup your Mac should be a part of Mac user’s habit.

Step 3 Erase High Sierra

This is much simpler than you think.

1. Connect to Time Machine by clicking the Spotlight search, typing Time Machine, and choosing the prompted option.

2. Restart your Mac in Recovery Mode by pressing Command + R.

3. At the macOS Utilities screen, press Disk Utility.

4. Click Continue and then choose Startup Disk.

5. Click on Erase. Choose a new disk name (mine is Macintosh HD and yes, I am not creative) and select Mac OS Extended (Journaled) format at the Format menu.

6. Now that restart your Mac by pressing Alt/Option and select the boot drive you created.

Step 4 Restore the backup you saved before

After the installation process is finished, use Time Machine or the external disk you manually used to back up your Mac to restore the data.

If you’re restoring from Time Machine, you’ll again have to reboot, press Command+R and go to Disk Utility. Choose the most recent backup and click on Continue.

Downgrading High Sierra could carry with a number of problems if you do not back up the document that you have run in High Sierra. Make sure you have a copy of everything that is important to you. Also, you ought to have some patience handling and waiting for the whole process.