Whether you need to better organize your hard drive or resolve disk errors, Disk Utility is the tool for the job. Built into macOS, Disk Utility is tucked away in the Utilities folder, which is found inside the Applications folder, but is easy to locate using Spotlight – which you trigger by pressing Command+Space Bar and then just type Disk Utility.
The tool displays details and a graph of your hard drive configuration, showing the overall capacity as well as the used and free space and the various volumes.
Over the years Disk Utility has been overhauled a few times, so the options may be slightly different depending on the version of macOS you are using. For example, in Mac OS X El Capitan Disk Utility was redesigned and many of the features evolved or were removed. There were also a few changes in macOS High Sierra thanks to the new file format Apple introduced: APFS. And when Catalina arrived a new Macintosh HD – Data volume started showing alongside a read-only Macintosh HD system volume.
There are a number of reasons why you might want to format a drive. Perhaps you want to wipe your startup drive so you can perform a fresh install of OS X, maybe you want to encrypt an external storage drive that you use for work, or you might wish to create a partition for Windows or a different version of the Mac operating system.
There are various file formats that you might want to use including:
Apple File System (APFS) – Apple’s filing system since macOS 10.13.
Mac OS Extended – Apple’s filing system prior to macOS 10.13.
and MS-DOS (FAT) and ExFAT – for compatibility with Windows.
Disk Utility is able to create a disk image of contents of a folder which you can then transfer to another Mac, an archive, or any location that doesn’t accept folders.
It’s similar to compressing the folder into a zip archive, but the benefit is that you can not only use disk image compression to save space, but can also take advantage of Apple’s encryption for the disk image.
You may wish to partition a disk to divide it into separate containers or because you want to install multiple operating systems. How you do this will depend on the version of macOS you are running. On newer Macs rather than create a partition you should create a volume.