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APFS (Apple File System) is an Apple file system optimized for solid state drives (SSDs) and flash-based
storage systems, though it also works with hard disk drives (HDDs). It was first introduced with the release of
macOS High Sierra (version 10.13). APFS can only be read by Macs running High Sierra or later.
When choosing between Apple file systems, consider the following:
Windows cannot natively read or write to APFS or HFS+ volumes. If you need cross-platform
compatibility, you should format the drive in exFAT.
If you intend to use your drive with Time Machine:
The default format for macOS Big Sur (version 11) and later is APFS.
The default format for macOS Catalina (version 10.15) and earlier is HFS+.
If you intend to use your drive to move files between Macs running older OS versions, consider
formatting your drive in HFS+ rather than APFS.
macOS file systems and Android: Formatting your drive for macOS may not be supported with
connections to Android mobile devices.
Learn more
For additional considerations when choosing a file system format, see File System Format Comparisions.
Formang instrucons
For instructions on formatting your drive, see How to format your drive.