APFS
Also known as: Apple File System, apfs format, Mac file system
APFS (Apple File System) is the default file system on modern iPhones, iPads, and Macs. It is built for flash storage and adds features like instant copies (clones), space-efficient snapshots, and strong encryption.
- Default file system on iPhone, iPad, and modern Mac
- Built for flash (SSD) storage, replaced HFS+ in 2017
- Snapshots and clones save space but can look like used storage
Where APFS is used
Apple introduced APFS in 2017 to replace the older HFS+ format. It now runs on iPhone, iPad, Apple Watch, and Macs with macOS High Sierra or later. It is optimized for the flash storage (SSD) inside these devices rather than spinning hard drives.
Two of its features directly affect storage math. Clones let the system duplicate a file instantly by sharing data until one copy changes, and snapshots capture the disk state at a point in time using very little extra space.
APFS and storage space
APFS snapshots are why a Mac or iPhone sometimes shows storage that is "in use" but seemingly unaccounted for. Local snapshots — for example, ones Time Machine keeps on the Mac — count as used space until they age out, but the system reports them as purgeable and reclaims them automatically when you need room.