Apple File System

Apple File System was announced at Apple's developers’ conference (WWDC) in June 2016 as a replacement for HFS+, which had been in use since 1998.{{cite web |first=Seth |last=Weintraub |title=Apple File System (APFS) announced for 2017, scales 'from Apple Watch to Mac Pro' and focuses on encryption |url=https://9to5mac.com/2016/06/13/apple-file-system-apfs/ |website=9to5Mac |date=June 13, 2016 |access-date=March 27, 2017 |url-status=live |archive-url=https://web.archive.org/web/20170328195315/https://9to5mac.com/2016/06/13/apple-file-system-apfs/ |archive-date=March 28, 2017 |df=mdy-all }}{{cite web |first=Lee |last=Hutchinson |title=New file system spotted in macOS Sierra [Updated] |url=https://arstechnica.com/apple/2016/06/new-apfs-file-system-spotted-in-new-version-of-macos/ |website=Ars Technica |publisher=Condé Nast |date=June 13, 2016 |access-date=March 27, 2017 |url-status=live |archive-url=https://web.archive.org/web/20170328195529/https://arstechnica.com/apple/2016/06/new-apfs-file-system-spotted-in-new-version-of-macos/ |archive-date=March 28, 2017 |df=mdy-all }} APFS was released for 64-bit iOS devices on March 27, 2017, with the release of iOS 10.3, and for macOS devices on September 25, 2017, with the release of macOS 10.13.{{cite web |first=Juli |last=Clover |title=Apple Releases iOS 10.3 With Find My AirPods, APFS, App Store Review Tweaks and More |url=https://www.macrumors.com/2017/03/27/apple-releases-ios-10-3/ |website=MacRumors |date=March 27, 2017 |access-date=March 27, 2017 |url-status=live |archive-url=https://web.archive.org/web/20170327194444/https://www.macrumors.com/2017/03/27/apple-releases-ios-10-3/ |archive-date=March 27, 2017 |df=mdy-all }}{{cite web |first=Tom |last=Warren |title=Apple is upgrading millions of iOS devices to a new modern file system today |url=https://www.theverge.com/2017/3/27/15076244/apple-file-system-apfs-ios-10-3-features |website=The Verge |publisher=Vox Media |date=March 27, 2017 |access-date=March 27, 2017 |url-status=live |archive-url=https://web.archive.org/web/20170327184802/http://www.theverge.com/2017/3/27/15076244/apple-file-system-apfs-ios-10-3-features |archive-date=March 27, 2017 |df=mdy-all }}

Apple released a partial specification for APFS in September 2018 which supported read-only access to Apple File Systems on unencrypted, non-Fusion storage devices. The specification for software encryption was documented later.{{cite web |title=Apple File System Reference |url=https://developer.apple.com/support/downloads/Apple-File-System-Reference.pdf |publisher=Apple Developer}}

The file system can be used on devices with relatively small or large amounts of storage. It uses 64-bit inode numbers, and allows for more secure storage by using a technology called Data Protection. The APFS code, like the HFS+ code, uses the TRIM command for better space management and performance. It may increase read-write speeds on iOS and macOS, as well as space on iOS devices, due to the way APFS calculates available data.{{cite web|url=https://www.joe.co.uk/tech/updating-iphone-will-give-one-major-benefit-119704|title=Updating your iPhone will give you one major benefit|author=Alan Loughnane|website=joe.co.uk|date=April 2017 |url-status=live|archive-url=https://web.archive.org/web/20170520045551/https://www.joe.co.uk/tech/updating-iphone-will-give-one-major-benefit-119704|archive-date=May 20, 2017|df=mdy-all}}

APFS uses the GPT partition scheme. Within the GPT scheme are one or more APFS containers (partition type GUID is {{mono|7C3457EF-0000-11AA-AA11-00306543ECAC}}). Within each container there are one or more APFS volumes, all of which share the allocated space of the container, and each volume may have APFS volume roles. macOS Catalina (macOS 10.15) introduced the APFS volume group, which are groups of volumes that Finder displays as one volume. APFS firmlinks lie between hard links and soft links and link between volumes.

In macOS Catalina the {{mono|System}} volume role (usually named "Macintosh HD") became read-only, and in macOS Big Sur (macOS 11) it became a signed system volume (SSV) and only volume snapshots are mounted. The {{mono|Data}} volume role (usually named "Macintosh HD - Data") is used as an overlay or shadow of the {{mono|System}} volume, and both the {{mono|System}} and {{mono|Data}} volumes are part of the same volume group and shown as one in Finder.

Clones allow the operating system to make efficient file copies on the same volume without occupying additional storage space. Changes to a cloned file are saved as delta extents, reducing storage space required for document revisions and copies. There is, however, no interface to mark two copies of the same file as clones of the other, or for other types of data deduplication.

The feature is automatically available when you copy any files using the Finder application, which is macOS's default file manager, but not when using the cp command.{{cite web|title=A ZFS developer’s analysis of the good and bad in Apple’s new APFS file system|website=Ars Technica|date=2016-06-26|url=https://arstechnica.com/gadgets/2016/06/a-zfs-developers-analysis-of-the-good-and-bad-in-apples-new-apfs-file-system/|ref={{sfnref|Ars Technica|2016}}|access-date=2025-02-17|quote="Side note: Finder copy creates space-efficient clones, but cp from the command line does not."}} To do that on the command-line, the cp utility on macOS has a -c parameter that allows it to use the clonefile system call.{{cite web|title=[dedup] Use APFS clone (CoW) on macOS · Issue #219 · pkolaczk/fclones|website=GitHub|date=2023-08-10|url=https://github.com/pkolaczk/fclones/issues/219|access-date=2025-02-17}}

APFS volumes support snapshots for creating a point-in-time, read-only instance of the file system.

Apple File System natively supports full disk encryption, and file encryption with the following options:

• no encryption
• single-key encryption
• multi-key encryption, where each file is encrypted with a separate key, and metadata is encrypted with a different key.

APFS supports 64-bit inode numbers, supporting over 9 quintillion files (2⁶³) on a single volume.{{cite web|url=https://developer.apple.com/documentation/foundation/file_system/about_apple_file_system|author=Apple Inc|title=Apple File System Guide (Features)|access-date=December 16, 2023|df=mdy-all}}

Apple File System uses checksums to ensure data integrity for metadata but not for the actual user data, relying instead on error-correcting code (ECC) mechanisms in the storage hardware.{{cite web|url=http://dtrace.org/blogs/ahl/2016/06/19/apfs-part5/|author=Adam Leventhal|date=June 19, 2016|title=APFS in Detail: Data Integrity|url-status=live|archive-url=https://web.archive.org/web/20160621060302/http://dtrace.org/blogs/ahl/2016/06/19/apfs-part5/|archive-date=June 21, 2016|df=mdy-all}}

Apple File System is designed to avoid metadata corruption caused by system crashes. Instead of overwriting existing metadata records in place, it writes entirely new records, points to the new ones and then releases the old ones, an approach known as redirect-on-write. This avoids corrupted records containing partial old and partial new data caused by a crash that occurs during an update. It also avoids having to write the change twice, as happens with an HFS+ journaled file system, where changes are written first to the journal and then to the catalog file.

APFS supports transparent compression on individual files using Deflate (Zlib), LZVN (libFastCompression), and LZFSE. All three are Lempel-Ziv-type algorithms. This feature is inherited from HFS+, and is implemented with the same AppleFSCompression / decmpfs system using resource forks or extended attributes. As with HFS+, the transparency is broken for tools that do not use decmpfs-wrapped routines.{{cite web |last1=Søgaard |first1=Jens K. |title=How do I enable transparent compression on APFS? |url=https://apple.stackexchange.com/a/360124 |website=Ask Different |access-date=13 November 2019}}

APFS adds the ability to have multiple logical drives (referred to as volumes) in the same container where free space is available to all volumes in that container (block device).{{cite web |url=https://devstreaming-cdn.apple.com/videos/wwdc/2016/701q0pnn0ietcautcrv/701/701_introducing_apple_file_system.pdf |title=Introducing Apple File System |first1=Eric |last1=Tamura |first2=Dominic |last2=Giampaolo |author-link2=Dominic Giampaolo |date=2016 |access-date=May 28, 2022}}

While APFS includes numerous improvements relative to its predecessor, HFS+, a number of limitations have been noted.

APFS does not provide checksums for user data.{{Cite web|url=https://arstechnica.com/gadgets/2016/06/a-zfs-developers-analysis-of-the-good-and-bad-in-apples-new-apfs-file-system/|title=A ZFS developer's analysis of the good and bad in Apple's new APFS file system|date=June 26, 2016|website=Ars Technica}} It also does not take advantage of byte-addressable non-volatile random-access memory.{{cite web|url=https://www.zdnet.com/article/why-apples-apfs-wont-last-30-years/|title=Why Apple's APFS won't last 30 years|author=Robin Harris|date=June 24, 2016|website=ZDNet}}{{cite web| url=http://dtrace.org/blogs/ahl/2016/06/19/apfs-part1/ | author=Adam Leventhal | title=APFS in Detail: Overview | date=June 19, 2016 | access-date=October 1, 2017 | df=mdy-all}}

Enumerating files, and any inode metadata in general, is much slower on APFS when it is located on a hard disk drive (HDD). This is because instead of storing metadata at a fixed location like HFS+ does, APFS stores them alongside the actual file data. On SSDs, this fragmentation of metadata is inconsequential due to their lack of moving parts, but on HDDs, it leads to substantial performance degradation as the drive’s read/write heads must physically seek out scattered data fragments.{{cite web |title=An analysis of APFS enumeration performance on rotational hard drives |url=https://bombich.com/blog/2019/09/12/analysis-apfs-enumeration-performance-on-rotational-hard-drives |website=Carbon Copy Cloner |access-date=8 January 2020}}

Besides that, a key feature of APFS is "copy-on-write," which allows for rapid file duplication by creating references to the original data rather than copying it outright. This feature enables functionalities like snapshots and quick file copies. However, when files are modified after being copied, APFS creates new extents (data blocks) for the changes, leading to more fragmentation over time. This issue is exacerbated with applications like Time Machine, which creates multiple versions of files, further increasing fragmentation and slowing performance.{{cite web|title=APFS Is Not Yet Ready for Traditional Hard Drives|website=Larry Jordan|date=2017-12-03|url=https://larryjordan.com/blog/apfs-is-not-yet-ready-for-traditional-hard-drives/|ref={{sfnref|Larry Jordan|2017}}|access-date=2025-02-17}} As a result, APFS is generally not recommended for use on HDDs, particularly for workloads involving frequent file modifications, copying, or snapshot usage.{{cite web|last=Tim|first=OWC|title=Using APFS On HDDs ... And Why You Might Not Want To|website=Rocket Yard|date=2017-11-29|url=https://eshop.macsales.com/blog/43043-using-apfs-on-hdds-and-why-you-might-not-want-to/|access-date=2025-02-17}}

Unlike HFS+, APFS does not support hard links to directories.{{cite web|title=Apple File System Guide / Frequently Asked Questions|url=https://developer.apple.com/library/content/documentation/FileManagement/Conceptual/APFS_Guide/FAQ/FAQ.html|access-date=May 25, 2018|df=mdy-all}}{{cite web|last=Leventhal|first=Adam H.|url=https://arstechnica.com/gadgets/2016/06/a-zfs-developers-analysis-of-the-good-and-bad-in-apples-new-apfs-file-system/|title=A ZFS developer's analysis of the good and bad in Apple's new APFS file system|quote=APFS right now is incompatible with Time Machine due to the lack of directory hard links, a fairly disgusting implementation that likely contributes to Time Machine's questionable reliability.|website=Ars Technica|date=June 26, 2016}} Since the version of the Time Machine backup software included in Mac OS X 10.5 (Leopard) through macOS 10.15 (Catalina) relied on hard links to directories, APFS was initially not a supported option for its backup volumes.{{cite web|title=Disks you can use with Time Machine|url=https://support.apple.com/guide/mac-help/disks-you-can-use-with-time-machine-mh15139/mac|access-date=December 17, 2019|df=mdy-all}} This limitation was overcome starting in macOS 11 Big Sur, wherein APFS is now the default file system for new Time Machine backups (existing HFS+-formatted backup drives are also still supported).{{cite web |title=APFS changes in Big Sur |date=June 29, 2020 |url=https://eclecticlight.co/2020/06/29/apfs-changes-in-big-sur-how-time-machine-backs-up-to-apfs-and-more/ |access-date=26 November 2020}} macOS Big Sur's implementation of Time Machine in conjunction with APFS-formatted drives enables "faster, more compact, and more reliable backups" than were possible with HFS+-formatted backup drives.{{cite web |title=macOS Big Sur 11.0.1 Release Notes |url=https://developer.apple.com/documentation/macos-release-notes/macos-big-sur-11_0_1-release-notes |website=Apple |access-date=December 13, 2020}}{{cite news |last1=Cunningham |first1=Andrew |title=macOS 11.0 Big Sur: The Ars Technica review |url=https://arstechnica.com/gadgets/2020/11/macos-11-0-big-sur-the-ars-technica-review/ |access-date=6 March 2021 |publisher=Ars Technica |date=12 Nov 2020}}

• In March 2018, the APFS driver in High Sierra was found to have a bug that causes the disk encryption password to be logged in plaintext.{{cite web |title=Uh Oh! Unified Logs in High Sierra (10.13) Show Plaintext Password for APFS Encrypted External Volumes via Disk Utility.app |url=https://www.mac4n6.com/blog/2018/3/21/uh-oh-unified-logs-in-high-sierra-1013-show-plaintext-password-for-apfs-encrypted-external-volumes-via-disk-utilityapp |website=mac4n6 |date=March 21, 2018 |access-date=11 November 2019}}
• In January 2021, the APFS driver in iOS < 14.4, macOS < 11.2, watchOS < 7.3, and tvOS < 14.4 was found to have a bug that allowed a local user to read arbitrary files, regardless of their permissions.{{cite news |title=About the security content of iOS 14.4 and iPadOS 14.4 - Apple Support |url=https://support.apple.com/en-us/HT212146 |website=Apple Support |access-date=7 February 2021}}{{cite web |title=About the security content of macOS Big Sur 11.2, Security Update 2021-001 Catalina, Security Update 2021-001 Mojave - Apple Support |url=https://support.apple.com/en-us/HT212147 |website=Apple Support |access-date=7 February 2021}}{{cite web |title=About the security content of watchOS 7.3 - Apple Support |url=https://support.apple.com/en-us/HT212148 |website=Apple Support |access-date=7 February 2021}}{{cite web |title=About the security content of tvOS 14.4 - Apple Support |url=https://support.apple.com/en-us/HT212149 |website=Apple Support |access-date=7 February 2021}}

An experimental version of APFS, with some limitations, is provided in macOS Sierra 10.12.4. It is available through the command line diskutil utility. Among these limitations, it does not perform Unicode normalization while HFS+ does,{{Cite web|url=https://mjtsai.com/blog/2017/03/24/apfss-bag-of-bytes-filenames/|title=Michael Tsai - Blog - APFS's "Bag of Bytes" Filenames|first=Michael J.|last=Tsai}} leading to problems with languages other than English.{{Cite web|url=https://eclecticlight.co/2017/04/06/apfs-is-currently-unusable-with-most-non-english-languages/|title=APFS is currently unusable with most non-English languages|date=April 6, 2017|archive-url=https://web.archive.org/web/20170608180050/https://eclecticlight.co/2017/04/06/apfs-is-currently-unusable-with-most-non-english-languages/|archive-date=June 8, 2017|url-status=live}} Drives formatted with Sierra’s version of APFS may also not be compatible with later versions of macOS or APFS, and the Sierra version of APFS cannot be used with Time Machine, FileVault volumes, or Fusion Drives.{{Cite news|url=http://www.howtogeek.com/272741/how-to-format-a-drive-with-the-apfs-file-system-on-macos-sierra/|title=How to Format a Drive With the APFS File System on macOS Sierra|access-date=October 26, 2016|url-status=live|archive-url=https://web.archive.org/web/20161026171416/http://www.howtogeek.com/272741/how-to-format-a-drive-with-the-apfs-file-system-on-macos-sierra/|archive-date=October 26, 2016|df=mdy-all}}

Since macOS 10.13 High Sierra, all devices with flash storage are automatically converted to APFS.{{cite web | url=https://support.apple.com/en-gb/HT208018 | title=Prepare for APFS in macOS High Sierra | work=Apple.com | date=September 7, 2017 | access-date=September 19, 2017 | df=mdy-all}} As of macOS 10.14 Mojave, Fusion Drives and hard disk drives are also upgraded on installation.{{cite web | url=https://arstechnica.com/features/2018/09/macos-10-14-mojave-the-ars-technica-review/3/ | title=macOS 10.14 Mojave: The Ars Technica review | work=arstechnica.com | date=September 25, 2018 | access-date=December 20, 2018 | df=mdy-all}} The primary user interface to upgrade does not present an option to opt out of this conversion, and devices formatted with the High Sierra version of APFS will not be readable in previous versions of macOS. Users can disable APFS conversion by using the installer's startosinstall utility on the command line and passing --converttoapfs NO.{{cite web|last1=Trouton|first1=Rich|title=Using the macOS High Sierra OS installer's startosinstall tool to avoid APFS conversion|url=https://derflounder.wordpress.com/2017/09/26/using-the-macos-high-sierra-os-installers-startosinstall-tool-to-avoid-apfs-conversion/|website=Der Flounder|access-date=January 16, 2018|date=September 26, 2017|df=mdy-all}}

FileVault volumes are not converted to APFS as of macOS Big Sur 11.2.1. Instead macOS formats external FileVault drives as CoreStorage Logical Volumes formatted with Mac OS Extended (Journaled). FileVault drives can be optionally encrypted.{{fact|date=February 2021}}

iOS 10.3, tvOS 10.2, and watchOS 3.2 convert the existing HFSX file system to APFS on compatible devices.{{Cite web|url=https://github.com/jakepetroules/Filesystem|title=jakepetroules/Filesystem|website=GitHub|language=en|access-date=March 29, 2017}}

Despite the ubiquity of APFS volumes in today's Macs and the format's 2016 introduction, third-party repair utilities continue to have notable limitations in supporting APFS volumes, due to Apple's delayed release of complete documentation. According to Alsoft, the maker of DiskWarrior, Apple's 2018 release of partial APFS format documentation has delayed the creation of a version of DiskWarrior that can safely rebuild APFS disks.{{cite web | url=https://www.alsoft.com/diskwarrior5apfs | title=DiskWarrior 5.2 & Apple File System (APFS) | access-date=2020-06-28}} Competing products, including MicroMat's TechTool and Prosoft's Drive Genius, are expected to increase APFS support as well.

Paragon Software Group has published a software development kit under the 4-Clause BSD License that supports read-only access of APFS drives.{{cite web |title=Paragon Software Group Releases Free Paragon APFS SDK Community Edition for Software Developers, OEMs, Forensic Experts |url=https://www.paragon-software.com/paragon-software-group-releases-free-paragon-apfs-sdk-community-edition-for-software-developers-oems-forensic-experts/ |website=Paragon Software Group}} [https://github.com/Paragon-Software-Group/paragon_apfs_sdk_ce GitHub] An independent read-only open source implementation by Joachim Metz, libfsapfs, is released under GNU Lesser General Public License v3. It has been packaged into Debian, Fedora Linux, Rocky Linux, Red Hat Enterprise Linux and Ubuntu software repositories.{{cite web |title=libyal/libfsapfs |url=https://github.com/libyal/libfsapfs |website=GitHub |date=7 November 2019 |quote=Library and tools to access the Apple File System (APFS)}}{{Cite web |title=apfs-fuse - Fedora Packages |url=https://packages.fedoraproject.org/pkgs/apfs-fuse/apfs-fuse/ |access-date=2022-10-20 |website=packages.fedoraproject.org}}{{Cite web |url=https://rhel.pkgs.org/9/forensics-x86_64/apfs-fuse-20200928-1.el9.x86_64.rpm.html|title=apfs-fuse-20200928-1.el9.x86_64.rpm|website=rhel.pkgs.org}} Both are command-line tools that do not expose a normal filesystem driver interface. There is a Filesystem in Userspace (FUSE) driver for Linux called apfs-fuse with read-only access.{{cite web |last1=Ross |first1=Alistair |title=How to mount macOS APFS disk volumes in Linux |url=https://linuxnewbieguide.org/how-to-mount-macos-apfs-disk-volumes-in-linux/ |website=The Ultimate Linux Newbie Guide |date=23 February 2019}} ([https://github.com/sgan81/apfs-fuse Github]) An "APFS for Linux" project is working to integrate APFS support into the Linux kernel.{{cite web |title=linux-apfs/linux-apfs-rw: APFS module for linux, with experimental write support |url=https://github.com/linux-apfs/linux-apfs-rw |website=GitHub |publisher=APFS for Linux |date=4 Feb 2022}}

A commercial product, Paragon's APFS for Windows, allows for read and write support to APFS volumes in all versions of Windows from Windows 7 through Windows 11 and Windows Server 2008 R2 through Windows Server 2022, but it is unable to format or verify APFS volumes, and it cannot read APFS volumes which are hardware-encrypted against the Apple T2 security chip.{{cite web |title=APFS for Windows {{!}} Paragon Software |url=https://www.paragon-software.com/home/apfs-windows/ |website=Paragon Software Group |access-date=29 January 2024}}

• Comparison of file systems

:A.{{note label|disputed|A|none}}Disputed {{Cite web |title=libfsapfs/documentation/Apple File System (APFS).asciidoc at main · libyal/libfsapfs |url=https://github.com/libyal/libfsapfs/blob/main/documentation/Apple%20File%20System%20(APFS).asciidoc |access-date=2025-05-30 |website=GitHub |language=en}}

{{reflist|30em}}

• Apple Developer: [https://developer.apple.com/documentation/foundation/file_system/about_apple_file_system Apple File System Guide]
• Apple Developer: [https://developer.apple.com/support/apple-file-system/Apple-File-System-Reference.pdf Apple File System Reference]
• WWDC 2016: [https://developer.apple.com/videos/play/wwdc2016/701/ Introduction of APFS] by Apple software engineers Dominic Giampaolo and Eric Tamura
• [http://dtrace.org/blogs/ahl/2016/06/19/apfs-part1/ Detailed Overview of APFS] by independent file system developer Adam Leventhal

{{Filesystem}}

{{iOS}}

{{macOS}}

Category:2017 software

Category:Apple Inc. file systems

Category:Computer file systems

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