How do you force erase a disk on a Mac?

Forcing the erasure of a disk on a Mac is an effective way to securely wipe all data from the drive before selling, donating or recycling your device. Completely erasing a disk ensures that no sensitive information can be recovered, giving you peace of mind that your data is secure.

What Does Forced Erasure Mean on a Mac?

Forced erasure, also known as secure erase, is a process that overwrites all data on a drive to prevent recovery. When you normally delete files on a Mac, the references to those files are removed from the directory but the actual data remains on the drive. This means deleted files can often be recovered using data recovery software.

By forcibly erasing a disk, the drive is overwritten with random data to completely replace existing files and make recovery impossible. Forced erasure goes above and beyond the standard delete function to ensure complete data removal.

When Should You Force Erase a Disk?

Here are some common scenarios when forced erasure is recommended for Mac devices:

  • Selling or gifting your Mac – Erase personal data before passing your device on to a new owner
  • Disposing of an old Mac – Wipe information before recycling or throwing out an old computer
  • Repairing or returning a Mac – Protect sensitive data from technicians during servicing
  • Removing sensitive data – Ensure complete removal of financial records, passwords or other private information
  • Eliminating malware – Forced erasure can wipe any malicious programs that standard deletion may leave behind

In general, you should consider forced erasure any time you need to permanently destroy personal or sensitive information before parting with a Mac.

How Does Forced Erasure Work on a Mac?

Mac OS includes secured erase capabilities as part of the Disk Utility application. When activated, Disk Utility will perform multiple overwrite passes on the selected drive, replacing all recoverable data with meaningless randomly generated data.

Here’s an overview of how forced erasure works on a technical level:

  1. The erasure process is initialized through Disk Utility, selecting the drive to be wiped
  2. All existing data on the drive is overwritten with pseudo-random data
  3. By default, this overwrite process is repeated at least 2 times to ensure full coverage
  4. The pseudo-random data consists of 0s and 1s in no discernible order, providing no clues about the previously stored information
  5. With the data overwritten, all existing files and directory structures on the disk are irrecoverably destroyed
  6. The drive can then be reformatted and put back into use with all traces of old data securely erased

This intensive overwrite technique results in every sector of the drive being filled with meaningless gibberish, leaving no trace of recoverable files.

How to Force Erase an External Drive on a Mac

Erasing external drives is a common scenario for forced erasure. Here are the steps to securely wipe an external USB flash drive or hard drive on a Mac:

  1. Connect the external drive to your Mac if it isn’t already
  2. Launch the Disk Utility app (Finder > Applications > Utilities > Disk Utility)
  3. Select the external drive icon in the left pane of Disk Utility
  4. Click the Erase tab along the top menu bar
  5. In the pop-down next to Name, select “Mac OS Extended”
  6. Choose a name for the drive under Name (this can be changed later)
  7. Select the Scheme drop-down and choose “GUID Partition Map”
  8. Under Erase, pick “Most Secure 3-Pass Erase”
  9. Click Erase and enter your admin password to confirm

The Most Secure 3-Pass option will overwrite the drive three times, providing the strongest level of forced erasure. This process may take several hours to complete depending on the drive size. Once finished, the drive will be ready to use again with all prior data securely wiped.

How to Force Erase the Internal Hard Drive on a Mac

Erasing the internal drive requires booting from an external source and completely reformatting the Mac’s hard drive. Here is the basic process:

  1. Backup any important data from the internal drive
  2. Connect an external bootable drive or bootable installer media (USB stick, DVD, etc)
  3. Restart the Mac and hold Option during boot to select external boot
  4. Open Disk Utility from the external OS (Recovery mode on a bootable installer)
  5. Select the Mac’s internal drive icon
  6. Click Erase and choose a Most Secure 3-Pass erase
  7. Quit Disk Utility when finished erasing
  8. Run the OS installer to reinstall Mac OS on the blank internal drive
  9. Restart back into the newly installed system

This will completely wipe the original OS installation and data from the internal drive, leaving you with a freshly erased Mac.

How Long Does Forced Erase Take on a Mac?

The amount of time required to completely force erase a drive depends on a few factors:

  • Drive size – Larger drives take longer to overwrite multiple times
  • Connection type – External SSDs erase faster than external HDDs
  • Erase scheme – Multi-pass options take longer than single pass

As a general guideline, expect forced erasure to take:

Drive Type Erase Time
250GB HDD 1-2 hours
2TB External HDD 4-6 hours
500GB SSD 1-1.5 hours

Larger drives over 4TB may take over 12 hours for a full 3-pass secure erase. Be prepared for an extended process if force erasing very large internal or external drives.

Alternative Faster Erase Options

The default Most Secure 3-Pass option provides maximum overwrite coverage for complete data destruction. However, the multi-pass process can be slow. For less sensitive data, you can opt for one of these quicker erase options in Disk Utility:

  • Single Pass Erase – Overwrites drive once with zeroes. Less secure but much faster.
  • 3 Pass Erase – Overwrites with pseudo-random data, then zeroes, then pseudo-random again. Good security with improved performance over 3 Pass.
  • 7 Pass Erase – Overwrites drive 7 times. Maximum security outside of 3 Pass Most Secure option.

While not as fully secure as the 3 Pass Most Secure approach, these options can still provide reasonable drive erasure much faster. A single pass erase of a 2TB drive may take 2 hours instead of 6 hours for a 3 Pass Most Secure erase.

Can Deleted Files be Recovered After Forced Erasure?

No, the entire point of forced erasure is to prevent any possibility of recovering deleted data. The intensive overwrite process destroys all data beyond recovery. No file scanning or data recovery software can restore data after a full forced erase is completed.

That said, any new files written to the drive after erasing could potentially be recovered if deleted normally. For absolute security, the full forced erase process would need to be repeated each time you want to dispose of new data on the drive.

Maintaining proper backups is recommended when force erasing a drive containing any files you may want to keep. The erasure is permanent, so ensure you have copies of important data stored elsewhere before initializing a forced erase.

Should You Force Erase an SSD or HDD?

Force erasing is effective for securely wiping both HDDs and SSDs. However, there are a few differences between erasing hard disk drives (HDDs) and solid state drives (SSDs):

  • SSDs erase faster than HDDs due to better performance
  • Wear leveling on SSDs can leave data traces in unused areas after erasing
  • HDD platters retain almost no residual data traces after overwriting
  • Multiple overwrite passes are more important for fully erasing HDDs

For optimal security, use the Most Secure 3 Pass option when erasing either SSDs or HDDs. While SSD wear leveling can leave traces of older data, overwriting the entire visible drive space will still effectively destroy recoverable files in practice.

Can You Recover Data After Forcing an Erase on Mac?

No, recovering data after forcing an erase on a Mac drive is essentially impossible. The cryptographically secure multi-pass overwrite employed by Disk Utility destroys any possibility of file recovery.

Some examples of what is ineffective after forced erasure:

  • Scanning with recovery software will find no recoverable files or partitions
  • Sending the drive to a data recovery service will not work
  • Looking for file traces at the byte level will show only randomized data
  • Disassembling the physical drive cannot recover the overwritten data

The only way to regain the deleted data would be to restore from a backup taken prior to erasing the drive. With no backup, forced erase leads to permanent unrecoverable data loss.

Can Forced Erase be Stopped or Paused?

Disk Utility does not provide a built-in way to pause or stop a forced erase once initiated. This is an intentional security precaution to prevent the possibility of interrupting the overwrite process and potentially leaving remnants of old data due to an incomplete erasure.

The only way to stop the erasure is to force quit the Disk Utility application. However this is not recommended, as it could result in an unstable drive state or only partially overwritten data. It is best to allow the forced erase process to run to completion once started.

Plan ahead before beginning an erase by allocating sufficient time for larger drives. You cannot pause and resume from where it left off. The entire process must be completed in one pass for maximum security.

Is Forced Erase Necessary, or is Standard Delete Sufficient?

For highly sensitive data, forced erase is strongly recommended over standard deletion. While simply sending a file to the Trash may seem to remove it, standard deletion only removes pointers to the data while leaving it intact on the drive.

With advanced recovery tools, deleted files can often be salvaged from a drive that was only subjected to standard delete operations. For true peace of mind that your data cannot be recovered, perform a full forced erase.

Standard deletion may be sufficient for less critical temporary files. But for truly private information like financial records, legal documents or passwords, forced erase is the only way to fully prevent data recovery.

Can You Reinstall macOS After Forced Erase Without Losing Data?

Reinstalling macOS after a forced erase requires completely wiping the internal drive, so all prior data is lost. However, you can backup important files before erasing using Time Machine or another backup service.

To preserve your data, be sure to:

  1. Backup files off the internal drive before forced erase
  2. Boot to an external OS installer after erasing the internal disk
  3. Reinstall macOS on the blank internal drive
  4. Restore desired files from your backup

As long as you have backups, you can securely wipe the internal drive and restore your files after OS reinstallation. Without backups, all data will be lost when you force erase the boot drive.

What Other Secure Erase Options Exist for Macs?

Some other ways to securely erase full drives or individual files on a Mac include:

  • The srm terminal command – Overwrites files or devices multiple times
  • Apple’s FileVault encryption – Full drive encryption protects data if device is lost/stolen
  • Third party tools – Apps like Permanently Delete securely shred files
  • Physical destruction – Physically damaging drives prevents data recovery

While Disk Utility is the simplest option, power users may want to look into supplementary tools like srm and Permanently Delete for enhanced security erasing at a file level.

Can You Recover Files After Erasing External Hard Drive on Mac?

If an external hard drive is fully erased using the secure erase options in Disk Utility, files cannot be recovered. The cryptographic secure erase overwrites all data on the drive beyond forensic recovery.

However, files can potentially be recovered after a standard erase option (non-secure quick erase) is used. Standard erase simply removes file pointers without overwriting actual data. To prevent any chance of file recovery from an external drive, always use the Most Secure 3 Pass option.

Is Data Erased by Restoring a Mac from Time Machine Backup?

Restoring a Mac from a Time Machine backup will revert the system back to the state captured in the backup, with a few caveats:

  • Files and apps added since the backup was made will be wiped during restore
  • Restoring won’t modify personal data outside the backup set like documents
  • Full forced erase is required to overwrite all data traces from the current OS

So restoring from backup does not actually perform a full drive forced erase. User data outside the backup like documents and downloads remain intact after the restore. For true secure erase, you need to use Disk Utility’s overwrite options.


Securely erasing disks and drives is crucial when disposing of old Mac computers and external storage devices. By taking advantage of macOS’s built-in forced erase features, you can permanently destroy sensitive information.

The Most Secure 3 Pass erase option provides the strongest protection by overwriting all data on a drive multiple times. While the process can be slow for large drives, forced erase gives you peace of mind that your private data cannot be recovered.

Remember to back up any important files you may need before initializing forced erase on a drive. And take the necessary precautions to securely wipe your Mac or external devices before selling, donating or recycling your hardware.

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