If you plan to use your external drive with computers that run both operating systems, you should consider formatting your drive with the exFAT file system.

Neither Apple File System nor HFS+ works with Windows, however. Any drive formatted with HFS+ will work just fine with a Mac that's running macOS High Sierra or later. There are many benefits to switching from HFS+ to APFS, including better security thanks to native encryption, but the most important thing to note for external-drive shoppers is backward-compatibility. It's simply called the Apple File System (APFS), and it's the first format to be used across both Macs and iOS devices. With the release of the macOS High Sierra operating system, Cupertino ditched its venerable Mac OS Extended file system, commonly abbreviated as HFS+, and switched to an entirely new file system.