Partition a physical disk

Apple File System (APFS) allocates disk space on demand; however, you can manually manage APFS volume allocation if required.

1. Choose View > Show All Devices.

2. Select an existing APFS volume in the sidebar, then click the Add Volume button .

3. Enter a name for the new APFS volume.

4. Click the Format pop-up menu, then choose a format.

   • APFS: Uses the Apple File System format, recommended for volumes using macOS High Sierra.

   • APFS (Encrypted): Uses the Apple File System format and encrypts the partition.

   • APFS (Case-sensitive): Uses the Apple File System format and is case-sensitive to file and folder names. For example, folders named “Homework” and “HOMEWORK” are two different folders.

   • APFS (Case-sensitive, Encrypted): Uses the Apple File System format, is case-sensitive to file and folder names, and encrypts the partition. For example, folders named “Homework” and “HOMEWORK” are two different folders.

5. If you want to manually manage APFS volume allocation, click Size Options and enter values in the fields:

   • Reserve Size: The optional reserve size ensures that the amount of storage will remain available for this volume.

   • Quota Size: The optional quota size limits how much storage the volume can allocate.

   When you’re done, click OK.

6. Click Add.

1. Choose View > Show All Devices.

2. Select the device in the sidebar, then click the Partition button .

   Internal storage devices appear below the Internal section in the sidebar. External devices appear below the External section in the sidebar.

   When you select a volume that already has data on it, the pie chart shows a shaded area representing the amount of data on the volume and an unshaded area representing the amount of free space available for another volume. Disk Utility also reports whether the volume can be removed or resized.

   If you see a small volume with an asterisk, the partition is smaller than can be represented at the correct scale in the chart.

3. Click the Add button .

4. Click each volume in the pie chart on the left, then enter a name for it.

   For MS-DOS (FAT) and ExFAT volumes, the name must be eleven characters or fewer.

5. Enter the size or drag the divider to increase or decrease the size of each volume.

   

6. For each volume, click the Format pop-up menu, then choose a format.

   • APFS: Uses the Apple File System format, recommended for volumes using macOS High Sierra.

   • APFS (Encrypted): Uses the Apple File System format and encrypts the partition.

   • APFS (Case-sensitive): Uses the Apple File System format and is case-sensitive to file and folder names. For example, folders named “Homework” and “HOMEWORK” are two different folders.

   • APFS (Case-sensitive, Encrypted): Uses the Apple File System format, is case-sensitive to file and folder names, and encrypts the partition. For example, folders named “Homework” and “HOMEWORK” are two different folders.

   • Mac OS Extended (Journaled): Uses the Mac format (Journaled HFS Plus) to protect the integrity of the hierarchical file system.

   • Mac OS Extended (Journaled, Encrypted): Uses the Mac format, requires a password, and encrypts the partition.

   • Mac OS Extended (Case-sensitive, Journaled): Uses the Mac format and is case-sensitive to file and folder names. For example, folders named “Homework” and “HOMEWORK” are two different folders.

   • Mac OS Extended (Case-sensitive, Journaled, Encrypted): Uses the Mac format, is case-sensitive to folder names, requires a password, and encrypts the volume.

   • MS-DOS (FAT): Use for Windows volumes that are 32 GB or less.

   • ExFAT: Use for Windows volumes that are over 32 GB.

7. Click Apply.

   Click Show Details to view the step-by-step process of creating a new volume.

8. When Disk Utility is finished creating the volumes, click Done.

After you partition a storage device, an icon for each volume appears in both the Disk Utility sidebar and the Finder sidebar.

If you have multiple volumes formatted as Mac OS Extended, MS-DOS (FAT), or ExFAT on a device and one of them is running out of space, you may be able to enlarge it without losing any of the files on it.

To enlarge a volume, you must delete the volume that comes after it on the device, then move the end point of the volume you want to enlarge into the freed space. You can’t enlarge the last volume on a device.

1. Choose View > Show All Devices.

2. In the sidebar, select the device that contains the volume you want to enlarge, then click the Partition button .

3. In the pie chart on the left, select the volume you want to remove, then click the Remove button .

4. Click Apply.

   The volume is removed, reformatted, and all free space is assigned to the previous volume.

5. Click Done.

You can erase all volumes on a device and create new ones. For example, if you want to change the partition map of a USB, Thunderbolt, or other storage device from Master Boot Record to GUID Partition Map. If you simply want to erase a volume, see Erase a volume.

1. Choose View > Show All Devices.

2. Select the device in the sidebar you want to erase and repartition, then click the Erase button .

   Note: You can’t erase the device that contains your startup volume.

3. Enter a name for the initial volume.

4. Click the Map pop-up menu, then choose a format for the initial partition.

   For MS-DOS and ExFAT partitions, the name must be eleven characters or less.

   • GUID Partition Map: Used for all Intel-based Mac computers.

   • Master Boot Record: Used for Windows partitions that will be formatted as MS-DOS (FAT) or ExFAT.

   • Apple Partition Map: Used for compatibility with older PowerPC-based Mac computers.

5. Click Erase, then click Done.