APFS (Apple File System) is Apple’s modern file system for Macs and mobile devices. It became the default with macOS High Sierra and is also used by iOS, iPadOS, watchOS and tvOS. APFS is designed for flash storage. It uses copy-on-write to avoid in-place changes, which gives strong crash protection. It supports snapshots, so the system can freeze a point in time for fast backups and quick restores. Time Machine on recent macOS versions uses these snapshots. APFS allows cheap clones of files and folders on the same volume, so copies start small and grow only when data changes. Several volumes can share one APFS container, which lets free space be pooled and used where needed. Encryption is built in, with options that can protect metadata and file contents, and keys can be tied to each file. Metadata has checksums to detect corruption. APFS supports very large files, nanosecond timestamps, sparse files and TRIM on SSDs. It is case-insensitive by default on macOS, with a case-sensitive option. It replaced HFS Plus and does not use a traditional journal because copy-on-write serves the same goal. Hard links to files remain, but hard links to directories are not allowed. Outside Apple platforms, read or write support usually needs extra tools.
