HFS Plus
| Developer(s) | Apple Inc. |
|---|---|
| Full name | Hierarchical File System Plus |
| Introduced | January 19, 1998 with Mac OS 8.1 |
| Partition identifier |
Apple_HFS (Apple Partition Map)
0xAF (MBR) HFS and HFS+ Apple_HFSX (Apple Partition Map) when HFSX 48465300-0000-11AA- AA11-00306543ECAC (GPT) |
| Structures | |
| Directory contents | B-tree |
| File allocation | Bitmap |
| Bad blocks | B-tree |
| Limits | |
| Max. volume size | 8 exabyte |
| Max. file size | 8 exabyte |
| Max. number of files | 4,294,967,295 (232-1) |
| Max. filename length | 255 characters (255 UTF-16 encoding units, normalized to Apple-modified variant of Unicode Normalization Format D) |
| Allowed characters in filenames | Unicode, any character, including NUL. OS APIs may limit some characters for legacy reasons |
| Features | |
| Dates recorded | access, attributes modified, backed up, contents modified, created |
| Date range | January 1, 1904 – February 6, 2040 |
| Date resolution | 1 s |
| Forks | Yes |
| Attributes | Color (3 bits, all other flags 1 bit), locked, custom icon, bundle, invisible, alias, system, stationery, inited, no INIT resources, shared, desktop |
| File system permissions | Unix permissions, NFSv4 ACLs (Mac OS X v10.4 onward) |
| Transparent compression | Yes (on Mac OS X 10.6 and higher) |
| Transparent encryption | Yes (on Mac OS X 10.7 and up). Per-home directory encryption is available with AES using HFS+ formatted .dmg volumes on OS X versions prior to 10.7 but later than Mac OS X 10.3 |
| Other | |
| Supported operating systems | Mac OS 8.1, Mac OS 9, macOS/iOS/tvOS/watchOS/Darwin, Linux, Microsoft Windows (through Boot CampIFS drivers) |
HFS Plus or HFS+ is a file system developed by Apple Inc. It serves as the primary file system of macOS. HFS+ was developed to replace the Hierarchical File System (HFS) as the primary file system used in Macintosh computers (or other systems running the classic Mac OS). It is also one of the formats used by the iPod digital music player. HFS Plus is also referred to as Mac OS Extended or HFS Extended, where its predecessor, HFS, is also referred to as Mac OS Standard or HFS Standard. During development, Apple referred to this file system with the codename Sequoia.
HFS Plus is an improved version of HFS, supporting much larger files (block addresses are 32-bit length instead of 16-bit) and using Unicode (instead of Mac OS Roman or any of several other character sets) for naming items. Like HFS, HFS Plus uses B-trees to store most volume metadata, but unlike most other file systems, HFS Plus supports hard links to directories. HFS Plus permits filenames up to 255 characters in length, and n-forked files similar to NTFS, though until 2005 almost no system software took advantage of forks other than the data fork and resource fork. HFS Plus also uses a full 32-bit allocation mapping table rather than HFS's 16 bits, significantly improving space utilization with large disks.
HFS+ was introduced with the January 19, 1998 release of Mac OS 8.1.
With the release of the Mac OS X 10.2.2 update on November 11, 2002, Apple added optional journaling features to HFS Plus for improved data reliability. These features were easily accessible in Mac OS X Server, but only accessible through the command line in the standard desktop client.
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