Format a disk for Windows computers in Disk Utility on Mac
In Disk Utility on your Mac, you can format an external disk for a Windows computer.
WARNING: Formatting a disk or volume erases all the files on it. Save any files you need to another volume before formatting.
In the Disk Utility app on your Mac, choose View > Show All Devices.
In the sidebar, select the disk you want to format to use with Windows computers.
Click the Erase button .
Click the Scheme pop-up menu, then choose Master Boot Record.
Click the Format pop-up menu, then choose one of the following:
MS-DOS (FAT): Choose this format if the size of the disk is 32GB or less.
ExFAT: Choose this format if the size of the disk is over 32GB.
Enter a name for the volume.
The maximum length for the volume name is 11 characters.
Click Erase, then click Done.
You can also partition a disk using the Master Boot Record partition layout, which is compatible with Windows.