The reason? Mac and Windows each use different file systems.Īfter unboxing a new storage-based item, it’s a wise move to look into how to format a hard drive for Mac (or SD card, flash drive, etc.) to reduce the likelihood of unexpected corruption, data loss, or other performance issues. Out of the box these devices may function unreliably or even fail to work on Macs at all. Besides hard drives, two other notable examples of this hurdle are SD cards and USB sticks.