This may happen if the drive you want to erase is your startup disk and has the Mac operating system installed in it. In such a case, you will have to create an external bootable drive and boot from that drive. In the article below, we’ve listed some causes and fixes for disk utility not erasing your hard drive.
What Causes Hard Drive to Not Erase or Format?
How to Fix Disk Utility Won’t Erase Hard Drive?
You cannot erase a drive that has your current operating system installed. So you have to confirm that you are not choosing the wrong disk. If you’re certain about choosing the correct disk, then try one of these methods below:
Startup disk is selectedOutdated macCorrupt/bad sectorsMounted drive
Create New User
This step is a little workaround for erasing all data from your Mac. This step requires you to create a new administrator account and delete all old user data from the new account. These steps will guide you on how to do it:
Unmount Drive
If you can’t erase a drive, you can try to unmount the disk first. Unmounting the disk will stop all processes being run on the disk, which may be preventing your PC from formatting. Here’s how you do it.
Use First Aid
The first aid is a Disk utility feature that repairs any errors on your drive. It can also solve any problems that are preventing you from erasing your drive. Here’s how you run the first aid feature:
Recovery Mode
If it doesn’t work on a desktop environment, you can boot your Mac into recovery mode and try to erase the data from there. Follow these steps to learn how to do it:
Update macOS
An outdated operating system may cause the disk utility app to malfunction. Updating the operating system will fix any bugs as well. Here are the steps on how to update your macOS.
Reduce the Security Option
While erasing your drive, you can choose if you want to make your data recoverable or not. The slider ranges from Fastest to Most secure. As the name suggests, fastest means it’ll be fast, but the data may be recoverable, and Most secure means your old data will not be recoverable, but it’ll take a longer time to format.
