6 Steps to Format Mac Startup Disk with Disk Utility

Cassie Xie
Last updated: Sep 21, 2023
Summary: This post mainly introduces how to format Mac startup disk with Disk Utility.

If you want to format your Mac startup disk to fix severe problems and give your Mac a new fresh start, you can check the step-by-step guide below.

format Mac startup disk

How to Format Mac Startup Disk – 6 Steps

To format your Mac startup disk, follow the steps below.

Step 1. Back Up Data on Your Mac

Formatting the Mac startup disk will erase all data on the disk, including the Mac operating system and all your files. Before proceeding, make sure to back up all important data on your Mac to an external storage device or a cloud service.

Step 2. Boot Your Mac into Recovery Mode

Intel processor Mac: Press the Power button to turn on your Mac and immediately press and hold the Command + R keys simultaneously.

Apple M1/M1 Mac: press and hold the Power button until you get to the startup options screen. Click Options > Continue to access the macOS Recovery window.

Mac Recovery Mode

Step 3. Launch Disk Utility from macOS Recovery

Select Disk Utility in Mac Recovery Mode and click Continue to boot your Mac into Disk Utility.

Step 4. Format Mac Startup Disk

  • In Disk Utility, select your Mac startup disk from the left panel, usually named Macintosh HD or similar.
  • Click the Erase button at the top toolbar of Disk Utility.
  • Select the APFS format for the disk and choose the GUID Partition Map scheme.
  • Click the Erase button to proceed with formatting the Macintosh HD disk.

Step 5 (Optional). Reinstall macOS

After your Mac startup disk is formatted, you can exit Disk Utility and go back to the macOS Recovery window. Select the “Reinstall macOS” option to follow the on-screen instructions to reinstall macOS on the disk.

If you plan to reinstall macOS from another disk, make sure to have a macOS bootable USB installer or another startup disk available.

Step 6 (Optional). Restore Data

If you have made a backup for your Mac with Mac Time Machine or other methods, you may restore your important data.

When Need to Format Mac Startup Disk

Formatting Mac startup disk is a serious step that should only be taken in specific situations. Here are some scenarios where you might need to format your Mac's startup disk.

  • Severe disk issues that can’t be fixed, e.g., repeated crashes or freezing, severe data corruption, etc.
  • Stubborn virus or malware infection.
  • Intend to sell your Mac or transfer to a new Mac.
  • Optimize the system and improve performance.

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This post provides a step-by-step guide on how to format Mac startup disk with Disk Utility.

If you're unsure whether formatting is the right action for your situation, you may consider seeking advice from Apple Support or a professional technician who might recommend appropriate solutions.

For more Mac and iPhone tips, please visit https://www.drbuho.com/.

Cassie has been writing about technology for her entire career life - over 5 years. She enjoys diving into how Apple products work and then breaking it down in a way anyone can understand.