Macintosh HD vs. Macintosh HD Data: Difference Between Them

Cassie Xie
Last updated: Jun 3, 2024

This article will explain what Macintosh HD and Macintosh HD Data volumes are in Disk Utility. You will learn the main difference between them and which one to erase when reinstalling macOS, downgrading macOS, performing a clean install, or factory resetting your Mac.

After updating to Catalina or a later version of macOS, you'll notice in Disk Utility that your previous system volume is replaced by a volume called "Macintosh HD." Additionally, there is a new volume called "Macintosh HD - Data." What exactly are these two volumes and what is the difference between Macintosh HD and Macintosh HD Data?

In this article, we'll explain everything you need to know about Macintosh HD vs. Macintosh HD Data. Keep reading to get all your questions answered.

Macintosh HD vs. Macintosh HD Data: Definition & Difference

What is Macintosh HD?

macOS Catalina and newer macOS versions create two separate volumes on a Mac's internal hard drive - Macintosh HD and Macintosh HD - Data. This two-volume structure is designed to enhance the security and integrity of the operating system on Apple computers.

Macintosh HD is the default name for the primary system volume on a Mac, containing the macOS operating system and essential system files. These core macOS operating system files include boot files, system libraries, default applications, and other essential components that enable macOS to function correctly. These core files are typically located in the "System" and "Library" directories.

What is Macintosh HD - Data?

Macintosh HD - Data volume is the default name for the volume on a Mac that stores user data and applications. This includes downloaded files, user-specific settings, applications, and other information created or stored by the user while using this Mac computer. This data is typically stored in the user's home directory, which includes subfolders like Documents, Downloads, Desktop, Music, Pictures, and Movies.

Macintosh HD and Macintosh HD volumes in Disk Utility

Difference Between Macintosh HD and Macintosh HD Data

Based on the definitions, "Macintosh HD" and "Macintosh HD - Data" are clearly distinct and separate volumes on your Mac's hard drive. You can refer to the "Macintosh HD" as the system volume, while "Macintosh HD Data" is the user data volume.

Another main difference between Macintosh HD and Macintosh HD Data is whether they are writable. The Macintosh HD volume is read-only, preventing users from modifying its contents. This protection is essential for safeguarding the system against malware attacks and preventing accidental deletions or changes. In contrast, the "Macintosh HD - Data" volume is writable, allowing users to modify and save their personal files without affecting the core system files.

In Finder, you will see "Macintosh HD" listed in the left sidebar under Locations (if you have enabled the option to show hard disks in Finder), but you won't see the "Macintosh HD - Data" volume. That is because Finder presents these volumes as a unified experience under "Macintosh HD", allowing you to access your applications, system files, and user data seamlessly.

Macintosh HD vs. Macintosh HD Data - Which to Erase

By separating user data and applications from system files, macOS enhances security and system stability. However, this dual-volume setup can cause confusion during tasks like reinstalling macOS, downgrading macOS, performing a clean install, or factory resetting your Mac. Choosing the wrong volume to erase can lead to issues. For instance, you might see two "Macintosh HD - Data" volumes in Disk Utility.

Before erasing the "Macintosh HD" or "Macintosh HD - Data" volume, be sure to back up your Mac. This will allow you to restore your Mac to a previous stable state if anything goes wrong and recover your personal information if it is deleted.

Erase Macintosh HD for reinstalling macOS

Erasing Macintosh HD is not required to reinstall macOS. However, if you encounter issues installing macOS on the system volume or if your operating system is underperforming, you can erase Macintosh HD to eliminate any errors and ensure a smooth reinstallation.

To do this, boot your Mac into Recovery Mode, open Disk Utility from the macOS Utilities window, select "Macintosh HD" from the sidebar, click the Erase button, and choose Delete APFS Volume. Then follow the prompts to erase the volume.

Erase Macintosh HD in Recovery Mode

Delete Macintosh HD - Data and erase Macintosh HD for downgrading macOS

If you want to downgrade macOS to macOS Catalina or later, it will create a new set of Macintosh HD and Macintosh HD - Data volumes on your drive while retaining the previous Macintosh HD - Data volume. Therefore, before downgrading, you should ensure that the existing Macintosh HD - Data volume is deleted.

Restart your Mac into Recovery Mode. In the macOS Utilities window, open Disk Utility and select the volume labeled "Macintosh HD - Data". Use the minus volume icon on the top panel and confirm the deletion. Then erase the Macintosh HD volume in Disk Utility. Alternatively, you can choose Erase Volume Group to erase both Macintosh HD and Macintosh HD - Data volumes at once. Afterward, degrade your Mac using a Time Machine backup, a bootable installer, or the recoveryOS.

How to delete Macintosh HD Data

Erase Macintosh HD, Macintosh HD - Data, and other volumes for clean installing macOS or factory resetting Mac

If you want to factory reset your Mac or install a macOS operating system from scratch, you need to completely erase the existing system and user data, and then install a fresh copy of macOS. This includes erasing all volumes, including Macintosh HD, Macintosh HD - Data, and any other volumes you may have created.

To do this, enter Recovery Mode on your Mac and open Disk Utility from the macOS Utilities window. Select the Mac hard drive, usually labeled as Macintosh HD, not just the Macintosh HD volume. Click Erase on the top panel and follow the prompts to completely erase the Mac startup disk.

Macintosh HD vs. Macintosh HD Data FAQs

If you have more questions about Macintosh HD vs. Macintosh HD Data, here are the answers to some frequently asked questions.

  1. Can I delete Macintosh HD - Data?

    Yes, you can delete the Macintosh HD - Data volume. However, you cannot delete it while macOS is running; you need to do this in Disk Utility from Recovery Mode.

  2. What happens if you erase Macintosh HD Data?

    When the Macintosh HD Data volume is erased, all personal data, settings, and applications will be removed. This data will be permanently lost unless you have a backup.

  3. Should I reinstall macOS on Macintosh HD or Macintosh HD Data?

    You should always install macOS on Macintosh HD, as it is the system volume designated for storing the macOS operating system and system files.

  4. Why is my SSD called Macintosh HD?

    Macintosh HD stands for Macintosh Hard Drive. It has been the default label for the internal hard drive of Macs since the introduction of the original Macintosh operating system in 1984. Although your Mac is using a solid-state drive (SSD) now, Macintosh HD continues to be the default name.

Free Up More Space on Macintosh HD - Data

When your Mac is running low on free space, it indicates that the Macintosh HD - Data volume is occupying a significant amount of space. To reclaim space on your Mac, you'll need to clean up the Macintosh HD - Data volume (assuming you don't have other user-created volumes). For an efficient process, consider using BuhoCleaner, which provides a fast and comprehensive method to free up disk space on your Mac.

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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.