This guide will walk you through how to format drives for Mac OS on a Mac.

Important Info on Drives

• For stability and performance, most drives need reformatting. New drives often come with unnecessary partitions or bloatware; others are in the wrong format.  
• All external hard drives, even new ones, should be formatted to Mac OS Extended (Journaled).
• Note that formatting a drive will erase everything on the drive. If you have files that you need to preserve, move them to a different drive before proceeding.
• It is recommended to name your drive based on your NetID (e.g. abc123).
  • Only use letters, numbers, and underscores in the name of your drive.

To Check a Drive’s Format

1. Right click on a drive's icon and select Get Info. 
   1. If the drive doesn't appear on the desktop, you may also right click on it in Finder.
2. Look Under Format for Mac OS Extended (Journaled).

Even if your drive is formatted to Mac OS Extended (Journaled) straight out of the box, you should still reformat it before the first time you see it. 

To Format a Drive

1. Launch Disk Utility. You can access this application by navigating to Finder, Applications, Utilities
2. In the top left of the Disk Utility window, open the View menu and select Show All Devices. 
3.  Select the physical disk (a.k.a the "root" or "highest level" of the drive) from the side menu.
4. Click the Erase icon at the top right of the window.
5. In the Erase pop-up window, choose the following options: 
   1. Name: Your NetID (recommended) 
   2. Format: Mac OS Extended (Journaled)
   3. Scheme: GUID Partition Map
6. Click the Erase button. 
7. Once the erase process is complete, click the Done button.