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I have Mojave installed in my computer and I want to format my computer's hard drive.
 
I have Mojave installed in my computer and I want to format my computer's hard drive.
The hard drive that has the system on it? Then your computer won’t work. Or a different hard drive? If different, then use Disk Utility, which is an app included in Mojave.
 
Here is the answer:
1. You need a way to boot the Mac using an EXTERNAL drive that is bootable.
2. You then open Disk Utility and "aim it" at the internal drive (topmost item in DU's list, and you MUST first choose "show all devices" from the popup menu (if there is one)
3. You then click the "erase" button and choose "Mac OS extended with journaling enabled".
4. DU will then erase the disk and "format" it.
 
Here is the answer:
1. You need a way to boot the Mac using an EXTERNAL drive that is bootable.
2. You then open Disk Utility and "aim it" at the internal drive (topmost item in DU's list, and you MUST first choose "show all devices" from the popup menu (if there is one)
3. You then click the "erase" button and choose "Mac OS extended with journaling enabled".
4. DU will then erase the disk and "format" it.

5. remember, this will wipe anything on your computer drive, so be sure to back everything up first.
 
@Dsampedro give us some more info so we know we're telling you to do the right thing.
Am I to assume you have Mojave and are unhappy with it and want to downgrade to another macOS version?

Would be good to know why you want to wipe your hard drive, because once you've done that you will need to run internet recovery and theres various methods of downloading and installing specific operating systems.
 
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