254: How To Format External Hard Drives On Macs Running OS High Sierra

Mike Murphy
3 min readSep 5, 2018

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Are you getting error messages formatting external hard drives?

How To Format Hard Drives in Mac OS High Sierra

The Tutorial Overview

You will learn how to format external hard drives on a Mac running OS High Sierra (10.13). There is a 2:30 minute video tutorial at the end if you learn better by watching. This tutorial was inspired by me getting error messages while formatting brand new hard drives that have always been reliable and have never had issues with. I managed a photography studio for 8+ years and formatted hundreds of hard drives (maybe thousands), so this was not new territory for me.

So, why was I suddenly getting these error messages from my favorite hard drives? By the way, LaCie are my go-to external drives & Western Digital when I’m low on funds.

Are you getting this error message when trying to format external hard drives on your Mac?

The culprit Mac OS High Sierra Operating System made one small change in Disk Utility that has caused many people to get error messages and this tutorial will show you the simple fix. For the life of me, I cannot understand why Apple would hide this setting by default.

How To Format A Hard Drive on Macs Running OS High Sierra 10.13:

Before you begin:
• Plug in External Hard Drive to Mac (USB or Thunderbolt)
• If possible, connect directly to computer instead of a hub.

  1. Open Disk Utility
    - Located in the Applications folder in another folder called ‘Utilities’
    - Open Finder…Click Go in the Menu Bar up top… Click Utilities
    - Or, Open Applications Folder…Click Utilities Folder…Open Disk Utility
  2. Click View Dropdown Menu, Select ‘Show All Devices’
    - Note: This is where ‘Show Sidebar’ is if you do not see drives
  3. Select Top Volume of Hard Drive you want to Format

4. Press Erase in Top Center

5. Name Hard Drive

6. Format:

  • Choose APFS or Mac OS Extended (Journaled)
  • APFS is the newer version of Mac OS Extended. Either one is fine for now.

7. Scheme:

  • Choose GUID Partition Map

8. Click Erase

9. Wait for green checkmark

10. Check Desktop Hard Drive is now formatted and mounted on desktop

11. Get Info: Select hard drive, press Cmd+i to get info if you want to verify everything looks good on drive.

12. All done. Let me know if you have any questions.

If you need help:

Email Me: mike@mikemurphy.co

Video Tutorial:

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Mike Murphy

Podcast & Tech Handyman. I make tutorials and help people figure things out. Email: mike@mikemurphy.co