The external hard drive must be reformatted for use with a Mac, as it is preformatted for Windows at the factory. For large amounts of data on a Mac, we recommend formatting with APFS or Mac OS Extended, not exFAT. You can easily do this with the macOS utility "Disk Utility" by selecting the hard drive, clicking on "Erase" and selecting the appropriate Mac format. The hard drive is then fully compatible and is also suitable for Time Machine backups.