FAT32 is a universal format that is compatible with Mac OS X, Windows, Linux and DOS systems. Format your removable flash drive to FAT32 with your Mac if you anticipate using the drive with more than one operating system. You can reformat disks in Mac OS X Yosemite using the Disk Utility in the Utilities folder.
Insert a flash drive into your Mac's USB port. The drive icon appears on your desktop.
Double-click the "Utilities" folder in the Applications section in Finder.
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Double-click "Disk Utility." This utility allows you to format, partition or otherwise modify disks.
Choose your flash drive from the list of disks on the left side of the utility. Click the "Erase" tab to access the disk-formatting settings.
Choose "MS-DOS (FAT)" from the format drop-down list.
Click "Erase..." to remove all the information on the flash drive and reformat it to the chosen format.
Right click the drive on the desktop and choose "Get Info."
Confirm that the format of your flash drive is now MS-DOS (FAT32). You can now use the flash drive freely with your Mac and with other operating systems.