Force erasing a disk on a Mac completely wipes the hard drive by overwriting all of the existing data with zeroes. This is useful when you want to permanently erase all of the contents on a drive before selling or giving away your Mac. It helps prevent personal files or sensitive data from being recovered by someone else.
A standard erase would simply delete references to the files on a drive, but advanced data recovery software could potentially still recover the files later. Force erasing overwrites the actual raw data, making it far more difficult for any deleted files to ever be recovered.
Force erasing is also recommended before reinstalling macOS to fix any disk errors, or starting fresh with a clean operating system install.
When To Force Erase a Disk
There are a few key scenarios when you may want to do a force erase of your Mac’s disk:
- When selling or giving away your Mac – You’ll want to securely wipe the disk when selling or gifting your Mac to another person. This ensures no personal data or files are left behind that the new owner could access.
- Before reinstalling macOS – Doing a force erase provides a fresh slate if you plan to reinstall macOS and start over.
- Switching to a new hard drive – When replacing your existing hard drive with a new one, you’ll want to do a full erase of the old drive before physically removing it.
- Erase unreadable sectors – If your disk has bad sectors that cannot be read, a force erase will reset those sectors.
When selling or gifting your Mac, it’s especially important to do a full force erase. This scrubs the disk by overwriting all sectors with zeroes to prevent file recovery. Simply deleting files or reformatting is not enough, as data could still be retrievable. A force erase gives you peace of mind that no sensitive documents, emails, photos or financial data could be accessed by the next owner.
Back Up Your Data First
Before you force erase your Mac’s disk, it is extremely important to back up all your files and data. Erasing your disk will delete everything on it, so you want to make sure anything important is saved elsewhere first.
The best way to back up a Mac is using Apple’s Time Machine software. Time Machine automatically backs up everything on your Mac – documents, photos, music, apps, settings, etc. – and saves hourly snapshots so you can restore older versions of files if needed. You can back up to an external hard drive or AirPort Time Capsule (source).
To use Time Machine before erasing your disk (source):
- Connect an external hard drive or Time Capsule with enough storage space for your backup.
- Open System Preferences > Time Machine and select your backup drive.
- Click Back Up Now and let the initial backup complete.
With a current Time Machine backup, you can securely erase your Mac’s disk knowing your files are safely stored elsewhere. Always back up before drastic operations like erasing a disk.
Boot Into Recovery Mode
The first step to force erasing a disk on a Mac is to boot into Recovery Mode. Here are the steps to boot into Recovery Mode depending on if your Mac has an Intel processor or Apple silicon:
On an Intel-based Mac:
- Shut down your Mac.
- Press and hold the Command + R keys immediately after you see the Apple logo. Keep holding until you see the macOS Utilities window.
For more details, see this Apple support article.
On a Mac with Apple silicon:
- Shut down your Mac.
- Press and hold the power button until you see the startup options window.
- Click Options then click Continue.
For step-by-step instructions, refer to Apple’s guide.
Launch Disk Utility
The next step is to open Disk Utility. To do this:
1. Click on the Utilities menu at the top of the screen in Recovery Mode.
2. Select “Disk Utility” from the dropdown menu.
Disk Utility will launch, showing a list of available disks and volumes on your Mac. This is where you can select the disk you want to erase.
For reference, see: How to Recover Accidentally Erased Hard Drive/Deleted …
Select the Disk
The next step is to select the disk you want to erase in Disk Utility. On the left side of the Disk Utility window is a sidebar that shows available disks, containers, and volumes. Choose the disk you want to erase from this sidebar.
Make sure you select the correct disk, as erasing it will delete all data. If you have an external disk plugged in, be careful not to select your startup disk which contains your operating system. The sidebar clearly labels each disk, so double check you have the proper one chosen before continuing.
With the disk you want to erase selected, you can now reformat or erase it in the next steps.
Click Erase
Once you have selected the disk you want to erase in Disk Utility, click on the Erase button at the top of the window. This will open the Erase options where you can configure how you want to erase the disk.
You’ll first want to choose a Name for the erased disk, like “Macintosh HD” or something descriptive. Next, select a Format – this controls the file system that will be used. The default APFS is recommended for most Mac users. Finally, choose the Scheme – either GUID Partition Map for Macs or Master Boot Record for sharing disks with Windows PCs.
For example:
Name: Macintosh HD
Format: APFS
Scheme: GUID Partition Map
This will configure your erased disk with the Apple File System (APFS) and GUID partition scheme, ready for macOS installation.
Choose Security Options
When erasing a disk in Disk Utility, you can choose from different security options to determine how thoroughly your data is wiped from the disk. These options include:
Don’t Erase Data – This quick erase option simply removes references to the files on the disk, but doesn’t actually overwrite any data. Files could potentially be recovered with data recovery software.
Single-pass Zero Out Data – This writes zeros over the entire disk once to obscure the existing data. It provides basic security against recovery.
Three-pass Zero Out Data – This is the standard secure erase option. It writes zeros over the disk three times, making most data unrecoverable by common software. It meets U.S. Department of Defense standards.
Seven-pass Zero Out Data – For the most stringent security, this writes random numbers over the disk seven times. After overwriting with 35+ passes, it makes the previous data virtually irretrievable. It meets standards for top-secret information.
Selecting a more thorough erase like the Three-pass or Seven-pass options ensures your data cannot easily be recovered if the Mac or drive ends up in the wrong hands. It provides security and peace of mind when disposing of an old disk. The trade-off is it takes much longer than a standard erase. See this Apple discussion for more details.
Click Erase
Once you have selected the disk you want to erase in Disk Utility, click the “Erase” button in the toolbar. This will bring up a final confirmation prompt to erase the disk. Be absolutely certain you have the correct disk selected here, as once erased, all data on the disk will be permanently deleted.
Double check that the name of the disk listed matches the one you intend to erase. Then click the “Erase” button in this prompt to confirm and begin erasing the disk. According to Apple Support (source), you may see an additional prompt to enter your administrator password to authorize the erase.
The erase process can take some time depending on the size of the disk and the amount of data on it. The Disk Utility app will show the progress during the erase. Do not interrupt the process or shut down your Mac. Once completed, you will see a message that the erase was successful and can click “Done” to exit the erase prompt.
Reinstall macOS
After erasing your disk, you’ll need to reinstall the macOS operating system. Here are the steps to reinstall macOS using the macOS Recovery system:
Boot your Mac into Recovery Mode by restarting your computer and holding down the Command + R keys at startup. This will launch the macOS Recovery system.
After the macOS Utilities window appears, click on Reinstall macOS (or Reinstall OS X if using an older version). The installer will launch and you will be prompted to select the disk you erased to reinstall macOS onto.
Follow the onscreen prompts to complete the installation process. The macOS installer will download the latest version compatible with your Mac model. Be patient as this may take awhile depending on your internet connection speed.
If the installer runs into any errors or says there is not enough space, you may need to fully erase the disk first using Disk Utility in Recovery Mode before attempting to reinstall. This will format the disk and free up space for macOS to install cleanly.
Once the installation is complete, you will be booted back into a fresh macOS setup. You can then restore your apps and data from a backup.
For more details, see this guide from CertSimple on reinstalling macOS without Wi-Fi.