How to Format an External USB Drive for Mac
External USB hard drives are lightweight, portable and inexpensive. They are great for backing up data, creating extra storage space on your computer and transferring large amounts of data between two or more computers. Macs and PCs use different file systems, so an external USB hard drive that has been formatted to work only with Windows will need to be formatted for a Mac before you can use it with your Apple computer.
Click on "Finder," then "Applications," then "Utilities."
Double-click "Disk Utilities."
Click on the USB drive in the left column.
Go to the "Erase" tab. Click on the "Volume Format" menu and select "Mac OS X Extended."
Click the "Erase" button. When the dialog box asking you to confirm the erase appears, click the "Erase" button again.
Tips & Warnings
- Formatting a hard drive will erase all the contents of the drive.