Editing Universal Disk Format

{{short description|Vendor-neutral file system, used in practice for DVDs and other optical discs}}
{{Use dmy dates|date=September 2019}}
{{Infobox filesystem
| name                    = UDF
| full_name               = Universal Disk Format
| developer               = [[International Organization for Standardization|ISO]]/[[International Electrotechnical Commission|IEC]], [[Ecma International]], [[Optical Storage Technology Association|OSTA]]
| introduction_os         = 
| introduction_date       = {{Start date and age|1995}}
| partition_id            = Not assigned but suggested:<ref>{{cite web|url=https://serverfault.com/a/829172|title=Serverfault answer for: What is the partition id / filesystem type for UDF?}}</ref><br />{{mono|[[Partition type#PID 07h|0x07]]}} ([[Master boot record|MBR]])<br />{{mono|[[Basic Data Partition|EBD0A0A2-B9E5-4433-87C0-68B6B72699C7]]}} ([[GUID Partition Table|GPT]])
| file_struct             = 
| bad_blocks_struct       = 
| max_filename_size       = 255 bytes (path 1023 bytes{{efn|name="note-43"|This restriction might be lifted in newer versions.}})
| max_files_no            = 
| max_volume_size         = 2 [[Tebibyte|TiB]] (with 512-byte sectors), 8 TiB (with 2 KiB sectors, like most optical discs), 16 TiB (with 4 KiB sectors){{efn|2<sup>32</sup> × ''block size''}}<ref>{{cite web |url=https://sites.google.com/site/udfintro/ |title=Wenguang's Introduction to Universal Disk Format (UDF) |at=Section 5.1 Highlight of the UDF Format |date=1 February 2009 |website=Google Sites |access-date=16 July 2014 }}</ref>
| max_file_size           = 16 [[Exbibyte|EiB]]
| filename_character_set  = Any 16-bit [[Unicode]] [[Code point]] excluding [[Byte order mark|U+FEFF]] and [[U+FFFE]]
| dates_recorded          = creation, archive, modification (mtime), attribute modification (ctime), access (atime)<!--double check-->
| date_range              = :24:00:00.000, 1 January 1 (UTC) {{spaced en dash}} 23:59:59.999, 31 December 9999 (UTC) <ref>[https://www.ecma-international.org/wp-content/uploads/ECMA-167_3rd_edition_june_1997.pdf ECMA 167 third edition, June 1997]</ref>
| date_resolution         =[[Microsecond]] 
| forks_streams           = Yes
| attributes              = Various
| file_system_permissions = POSIX
| compression             = No
| directory_struct        = 
| encryption              = 
| OS                      = Various
}}

'''Universal Disk Format''' ('''UDF''') is an [[open format|open]], vendor-neutral [[file system]] for [[computer data storage]] for a broad range of media. In practice, it has been most widely used for [[DVD]]s and newer [[optical disc]] formats, supplanting [[ISO 9660]]. Due to its design, it is very well suited to incremental updates on both [[Write once read many|write-once]] and re-writable [[Optical disc|optical media]]. UDF was developed and maintained by the [[Optical Storage Technology Association]] (OSTA).

In engineering terms, Universal Disk Format is a [[profile (engineering)|profile]] of the specifications known as ISO/IEC 13346 and ECMA-167.<ref name=ecma167>{{cite web |url = http://www.ecma-international.org/publications/files/ECMA-ST/Ecma-167.pdf |title = ECMA-167 – Volume and File Structure for Write-Once and Rewritable Media using Non-Sequential Recording for Information Interchange}}</ref>

== Usage ==
Normally, [[optical disc authoring software|authoring software]] will master a UDF file system in a batch process and write it to optical media in a single pass. But when [[packet writing]] to rewritable media, such as [[CD-RW]], UDF allows files to be created, deleted and changed on-disc just as a general-purpose [[filesystem]] would on removable media like [[floppy disk]]s and [[USB flash drive|flash drive]]s. This is also possible on write-once media, such as [[CD-R]], but in that case the space occupied by the deleted files cannot be reclaimed (and instead becomes inaccessible).

Multi-session mastering is also possible in UDF, though some implementations may be unable to read disks with multiple sessions.{{efn|Multi-session mastering has always been part of the UDF specification. See [UDF 2.01/6.10.1], though earlier documents were not very clear that the anchor offsets are specified to be from the last session.}}

== History ==
{{Optical disc authoring}}

The [[Optical Storage Technology Association]] standardized the UDF file system to form a common file system for all optical media: both for [[file system permissions|read-only]] media and for re-writable optical media. When first standardized, the UDF file system aimed to replace [[ISO 9660]], allowing support for both read-only and writable media. After the release of the first version of UDF, the [[DVD Consortium]] adopted it as the official file system for [[DVD-Video]] and [[DVD-Audio]].<ref name="OSTA - UDF Specifications">
{{cite web| url = http://www.osta.org/specs| title = OSTA – UDF Specifications}}</ref>

UDF shares the basic [[ISO 9660#Volume descriptor|volume descriptor]] format with ISO 9660. A "UDF Bridge" format is defined since 1.50 so that a disc can also contain a ISO 9660 file system making references to files on the UDF part.<ref>{{cite web |title=ECMA Technical Report TR/71: DVD Read-Only Disk File System Specifications |url=https://www.ecma-international.org/publications/files/ECMA-TR/ECMA%20TR-071.PDF |date=February 1998}}</ref>

=== Revisions ===

Multiple revisions of UDF have been released:<ref name="OSTA - UDF Specifications"/><ref>{{cite web| url = https://sites.google.com/site/udfintro/| title = Wenguang's Introduction to Universal Disk Format (UDF)}}</ref>
* Revision 1.00{{efn|name="history"|Mentioned only in history of Revision 1.02.}} (24 October 1995). Original Release.
* Revision 1.01{{efn|Not on the OSTA website. See [[#External_links|§ External links]]. Also listed in the history of revision 1.02.}} (3 November 1995). Added DVD Appendix and made a few minor changes.
* Revision 1.02<ref>{{cite web| url = http://www.osta.org/specs/pdf/udf102.pdf| title = OSTA Universal Disk Format Specification Revision 1.02}}</ref> (30 August 1996). This format is used by [[DVD-Video]] discs.
* Revision 1.50<ref>{{cite web| url = http://www.osta.org/specs/pdf/udf150.pdf| title = OSTA Universal Disk Format Specification Revision 1.50}}</ref> (4 February 1997). Added support for CD-R/W Packet Writing and (virtual) rewritability on CD-R/DVD-R media by introducing the Virtual Allocation Table (VAT) structure. Added sparing tables for defect management on rewritable media such as CD-RW, and DVD-RW and DVD+RW. Add UDF bridge.
* Revision 2.00<ref>{{cite web| url = http://www.osta.org/specs/pdf/udf200.pdf| title = OSTA Universal Disk Format Specification Revision 2.00}}</ref> (3 April 1998). Added support for Stream Files, Access Control lists, Power Calibration, real-time files (for [[DVD recording]]) and simplified directory management. VAT support was extended.
* Revision 2.01<ref>{{cite web| url = http://www.osta.org/specs/pdf/udf201.pdf| title = OSTA Universal Disk Format Specification Revision 2.01}}</ref> (15 March 2000) is mainly a bugfix release to UDF 2.00. Many of the UDF standard's ambiguities were resolved in version 2.01.
* Revision 2.50<ref>{{cite web| url = http://www.osta.org/specs/pdf/udf250.pdf| title = OSTA Universal Disk Format Specification Revision 2.50}}</ref> (30 April 2003). Added the Metadata Partition facilitating metadata clustering, easier crash recovery and optional duplication of file system information: All metadata like nodes and directory contents are written on a separate partition which can optionally be mirrored. This format is used by some versions of [[Blu-ray Disc|Blu-rays]] and most [[HD-DVD]] discs.
* Revision 2.60<ref name=udf260p>{{cite web| url = http://www.osta.org/specs/pdf/udf260.pdf| title = OSTA Universal Disk Format Specification Revision 2.60}}</ref> (1 March 2005). Added Pseudo OverWrite method for drives supporting pseudo overwrite capability on sequentially recordable media. Has read-only compatibility with UDF 2.50 implementations.{{rp|10}} (Some [[Blu-ray]]s use this format.)

UDF Revisions are internally encoded as [[binary-coded decimal]]s; Revision 2.60, for example, is represented as {{mono|0x0260}}.<ref name=udf260p/>{{rp|23}} In addition to declaring its own revision, compatibility for each volume is defined by the minimum read and minimum write revisions, each signalling the requirements for these operations to be possible for every structure on this image. A "maximum write" revision additionally records the highest UDF support level of all the implementations that has written to this image.<ref name=udf260p/>{{rp|34}} For example, a UDF 2.01 volume that does not use Stream Files (introduced in UDF 2.00) but uses VAT (UDF 1.50) created by a UDF 2.60-capable implementation may have the revision declared as {{mono|0x0201}}, the minimum read revision set to {{mono|0x0150}}, the minimum write to {{mono|0x0150}}, and the maximum write to {{mono|0x0260}}.

== Uses ==
While UDF was primarily developed for optical discs, it is also able to operate on other media such as hard disk drives and flash storage.<ref>{{cite web |url=https://www.man7.org/linux/man-pages/man8/mount.8.html |title=mount(8) – Linux manual page |access-date=2025-03-10 |quote=UDF is the "Universal Disk Format" filesystem defined by OSTA, the Optical Storage Technology Association, and is often used for DVD-ROM, frequently in the form of a hybrid UDF/ISO-9660 filesystem. It is, however, perfectly usable by itself on disk drives, flash drives and other block devices. }}</ref>

UDF was for well over a decade the only open-specification and [[cross-platform]]-supported file system without a file size limitation of 4 GiB (roughly 4.3 GB), until the open-sourcing of [[exFAT]] in 2019.{{efn|While [[ISO 9660]] is able to overcome its 4 GiB file size limitation by containing multiple file entries with the same name that refer to the same file (see [[ISO_9660#Directories_and_files|§ Directories and files]]), it is not well documented which operating systems support this feature, making its usefulness uncertain. Additionally, technical limitations make ISO 9660 unsuitable for hard disk and flash storage media anyway given that it was created only with factory-pressed [[CD-ROM]] that are never modified in mind. For example, files can not be added to an ISO 9660 file system without recreating it entirely or adding a new session (except if space was reserved for new files in advance on randomly writable media, but this hasn't been implemented so far as of 2025 given the lack of use), and the concept of multiple sessions does not exist on hard disks and flash storage given that they are randomly writable. }}{{efn| exFAT had been reverse-engineered well before Microsoft published its specification and as a result was de-facto (unofficially) open-source since around 2010, but unlike Microsoft, the developers of UDF made their specifications publicly available from the beginning.}}  "Cross-platform" here means supported by all three majorly used operating systems, Windows and Mac OS and Linux.<!-- sorted by how widely they are in use in the consumer space --><ref>In August 2019, Microsoft decided to lift some legal restrictions to exFAT and release its official specifications: {{cite web |url=https://opensource.microsoft.com/blog/2019/08/28/exfat-linux-kernel/ |title=exFAT in the Linux kernel? Yes! |date=2019-08-28 |website=Microsoft Open Source Blog  |access-date=2025-03-10 |language=en-US |author=John Gossman  }}; {{cite web |url=https://www.techradar.com/news/microsoft-is-bringing-its-exfat-patents-to-linux-and-open-source |title=Microsoft is bringing its exFAT patents to Linux and open source  |website=Tech Radar |date=2019-08-29 |access-date=2025-03-10 |language=en-GB |author=Anthony Spadafora }}</ref>

On Windows, formatting flash storage devices as UDF can not be accomplished through the graphical formatting widget, only through the command prompt.<!-- Probably the same for HDD but not mentioned in source. --><ref>{{cite web |title=How To Format a Flash Drive as UDF (Windows 7 & 10 Solution) • |url=https://www.getusb.info:443/how-to-format-a-flash-drive-as-udf-windows-7-10-solution/ |website=USB Powered Gadgets and more.. |access-date=25 April 2025 |date=2 April 2020}}</ref>

== Specifications ==
The UDF standard defines three [[file system]] variations, called "builds". These are:
* [[#Plain_build|''Plain'']] (Random Read/Write Access). This is the original format supported in all UDF revisions
* [[#VAT_build|''Virtual Allocation Table'']], also known as  ''VAT'' (Incremental Writing). Used specifically for writing to write-once media
* [[#Spared_(RW)_build|''Spared'']] (Limited Random Write Access). Used specifically for writing to rewritable media

=== Plain build ===
Introduced in the first version of the standard, this format can be used on any type of disk that allows random read/write access, such as [[hard disk]]s, [[DVD+RW]] and [[DVD-RAM]] media.  Metadata (up to v2.50) and file data is addressed more or less directly.  In writing to such a disk in this format, any physical block on the disk may be chosen for allocation of new or updated files.

Since this is the ''basic'' format, practically any operating system or file system driver claiming support for UDF should be able to read this format.

=== VAT build ===
Write-once media such as [[DVD-R]] and [[CD-R]] have limitations when being written to, in that each physical block can only be written to once, and the writing must happen incrementally. Thus the ''plain'' build of UDF can only be written to CD-Rs by pre-mastering the data and then writing all data in one piece to the media, similar to the way an [[ISO 9660]] file system gets written to CD media.

To enable a CD-R to be used virtually like a hard disk, whereby the user can add and modify files on a CD-R at will (so-called "drive letter access" on Windows), OSTA added the ''VAT'' build to the UDF standard in its revision 1.5. The VAT is an additional structure on the disc that allows [[packet writing]]; that is, remapping physical blocks when files or other data on the disc are modified or deleted. For write-once media, the entire disc is virtualized, making the write-once nature transparent for the user; the disc can be treated the same way one would treat a rewritable disc.

The write-once nature of CD-R or DVD-R media means that when a file is deleted on the disc, the file's data still remains on the disc. It does not appear in the directory any more, but it still occupies the original space where it was stored. Eventually, after using this scheme for some time, the disc will be full, as free space cannot be recovered by deleting files. Special tools can be used to access the previous state of the disc (the state before the delete occurred), making recovery possible.

Not all drives fully implement version 1.5 or higher of the UDF, and some may therefore be unable to handle VAT builds.

=== Spared (RW) build ===
Rewriteable media such as [[DVD-RW]] and [[CD-RW]] have fewer limitations than DVD-R and CD-R media. Sectors can be rewritten at random (though in packets at a time). These media can be erased entirely at any time, making the disc blank again, ready for writing a new UDF or other file system (e.g., ISO 9660 or [[CD-DA|CD Audio]]) to it. However, sectors of ''-RW'' media may "wear out" after a while, meaning that their data becomes unreliable, through having been rewritten too often (typically after a few hundred rewrites, with CD-RW).

The plain and VAT builds of the UDF format can be used on rewriteable media, with some limitations. If the plain build is used on a -RW media, file-system level modification of the data must not be allowed, as this would quickly wear out often-used sectors on the disc (such as those for directory and block allocation data), which would then go unnoticed and lead to data loss. To allow modification of files on the disc, rewriteable discs can be used like -R media using the ''VAT'' build. This ensures that all blocks get written only once (successively), ensuring that there are no blocks that get rewritten more often than others. This way, a RW disc can be erased and reused many times before it should become unreliable. However, it will eventually become unreliable with no easy way of detecting it. When using the ''VAT'' build, CD-RW/DVD-RW media effectively appears as CD-R or DVD+/−R media to the computer. However, the media may be erased again at any time.

The ''spared'' build was added in revision 1.5 to address the particularities of rewriteable media. This build adds an extra ''Sparing Table'' in order to manage the defects that will eventually occur on parts of the disc that have been rewritten too many times. This table keeps track of worn-out sectors and remaps them to working ones. UDF defect management does not apply to systems that already implement another form of defect management, such as [[Mount Rainier (packet writing)|Mount Rainier]] (MRW) for optical discs, or a disk controller for a hard drive.

The tools and drives that do not fully support revision 1.5 of UDF will ignore the sparing table, which would lead them to read the outdated worn-out sectors, leading to retrieval of corrupted data.

An [[overhead (computing)|overhead]] that is spread over the entire disc reserves a portion of the data storage space, limiting the usable capacity of a [[CD-RW]] with e.g. 650 MB of original capacity to around 500 MB.<ref name=PC-Thompson>{{cite book| url = https://books.google.com/books?id=kG8LcWfruOAC&pg=PT242 |title = ''"PC Hardware in a Nutshell: A Desktop Quick Reference"'' by Robert Bruce Thompson, Barbara Fritchman Thompson (2003) −– Chapter 11 (starting page 340): CD writers| isbn = 9780596552343| last1 = Thompson| first1 = Robert Bruce| last2 = Thompson| first2 = Barbara Fritchman| date = 24 July 2003| publisher="O'Reilly Media, Inc." }}</ref>

== Character set ==

The UDF specifications<ref name="OSTA - UDF Specifications"/> allow only one Character Set ''OSTA CS0'', which can store any [[Unicode]] [[Code point]] excluding U+FEFF and U+FFFE. Additional character sets defined in ECMA-167 are not used.<ref name=ecma167/>{{rp|at=7.2}}

Since Errata DCN-5157, the range of code points was expanded to all code points from Unicode 4.0 (or any newer or older version), which includes [[Plane (Unicode)#Supplementary Multilingual Plane|Plane]] 1–16 characters such as [[Emoji]]. DCN-5157 also recommends [[Unicode equivalence#Normalization|normalizing]] the strings to Normalization Form C.<ref name=dcn-5157>{{cite web|title=UDF 2.60 approved errata|url=http://www.osta.org/specs/pdf/udf260_errata.pdf|access-date=22 April 2018}}</ref>

The OSTA CS0 character set stores a 16-bit Unicode string "compressed" into 8-bit or 16-bit units, preceded by a single-byte "compID" tag to indicate the compression type. The 8-bit storage is functionally equivalent to [[ISO-8859-1]], and the 16-bit storage is [[UTF-16]] in big endian. 8-bit-per-character file names save space because they only require half the space per character, so they should be used if the file name contains no special characters that can not be represented with 8 bits only.<ref>[http://www.osta.org/specs/pdf/udf102.pdf UDF 1.02 specification]: 2.1.1 Character Sets (also present in later versions)</ref>

The reference algorithm neither checks for forbidden code points nor interprets [[Universal Character Set characters#Surrogates|surrogate pairs]], so like [[NTFS]] the string may be malformed.<ref name="OSTA - UDF Specifications" />{{rp|at=2.1.2, 6.4}} (No specific form of storage is specified by DCN-5157, but UTF-16BE is the only well-known method for storing all of Unicode while being mostly backward compatible with [[UCS-2]].)<ref name="dcn-5157" />

== Tools ==
Various tools have been developed to work with UDF file systems. For Linux, the <code>udftools</code> package contains several tools that can be used directly as a [[command-line interface]], but can also be called by other applications. 

The <code>mkudffs</code> tool creates a new UDF file system on a partition or a [[disk image]] file. The tool is [[symbolic link|symbolically linked]] from <code>mkfs.udf</code> for consistency with other <code>mkfs</code> tools.

<code>udfinfo</code> shows details of an UDF file system such as the volume label, version, counts of files and directories, and the status of the write protection flags. The volume label can be changed using the <code>udflabel</code> tool. 

The write protection flag can "seal" a file system once its [[Optical disc authoring|authoring]] is finished and no more changes to it are intended. For toggling the write protection setting which makes a file system read-only when activated, a tool called <code>udftune</code> was under development, but has not yet been included in the <code>udftools</code> package as of April 2025, following that its maintainer Pali Rohár has reportedly lost access to his GitHub account.<ref name=pali-github />

<code>wrudf</code> allows the user to modify an UDF file system interactively. For example, files can be copied and removed, and directories can be created and removed.

<code>pktsetup</code> implements [[packet writing]] through [[device file]]s named <code>/dev/pktcdvd0</code> and counting up. These device files are separate from the usual device files of optical drives named <code>/dev/sr0</code> (where "sr" means "SCSI ROM") and counting up.

<ref>[https://github.com/pali/udftools GitHub - pali/udftools: Linux tools for UDF filesystems and DVD/CD-R(W) drives]</ref>

== Compatibility ==
{{update|section|date=November 2020|reason=For many operating systems, the information is a decade old and may or may not reflect the current situation accurately}}
Many [[DVD player]]s do not support any UDF revision other than version 1.02. Discs created with a newer revision may still work in these players if the ISO 9660 bridge format is used. Even if an [[operating system]] claims to be able to read UDF 1.50, it still may only support the ''plain'' build and not necessarily either the ''VAT'' or ''Spared'' UDF builds.

[[macOS|Mac OS X]] 10.4.5 claims to support Revision 1.50 (see ''man mount_udf''), yet it can only mount disks of the ''plain'' build properly and provides no virtualization support at all. It cannot mount UDF disks with VAT, as seen with the Sony Mavica issue.<ref>{{cite web |url=http://support.apple.com/kb/TA26938?viewlocale=en_US |title=Sony Mavica UDF Compatibility Issue |date=19 February 2012 |website=Apple |access-date=16 July 2014 |url-status=dead |archive-url=https://web.archive.org/web/20120426172237/http://support.apple.com/kb/TA26938?viewlocale=en_US |archive-date=April 26, 2012}}</ref><ref>{{cite web |url=http://freecode.com/projects/udfmediareader |title=Mac OS X UDF Compatibility Issues |author=<!--Staff writer(s); no by-line.--> |date=11 July 2012 |website=Free(code) |access-date=16 July 2014}}</ref> Releases before 10.4.11 mount disks with Sparing Table but does not read its files correctly. Version 10.4.11 fixes this problem.<ref>{{cite web |url=https://www.apple.com/downloads/macosx/apple/macosx_updates/macosx10411comboupdateintel.html |title=Intel Update |date=14 November 2007 |website=Apple |access-date=16 July 2014 |url-status=dead |archive-url=https://web.archive.org/web/20100328145428/http://www.apple.com/downloads/macosx/apple/macosx_updates/macosx10411comboupdateintel.html |archive-date=March 28, 2010}}</ref><ref>{{cite web |url=https://www.apple.com/downloads/macosx/apple/macosx_updates/macosx10411comboupdateppc.html |title=PowerPC Update |date=14 November 2007 |website=Apple |access-date=16 July 2014 |url-status=dead |archive-url=https://web.archive.org/web/20100531005641/http://www.apple.com/downloads/macosx/apple/macosx_updates/macosx10411comboupdateppc.html |archive-date=May 31, 2010}}</ref>

Similarly, [[Windows XP]] Service Pack 2 (SP2) cannot read DVD-RW discs that use the UDF 2.00 sparing tables as a defect management system.<ref name="CD-ROM Drive">{{cite web |url=http://support.microsoft.com/kb/321640/en-us |title=CD-ROM Drive May Not Be Able to Read a UDF-Formatted Disc in Windows XP |publisher=Microsoft Support |url-status=live |archive-url=https://web.archive.org/web/20141215062925/http://support.microsoft.com/kb/321640/en-us |archive-date= Dec 15, 2014 }}</ref> This problem occurs if the UDF defect management system creates a sparing table that spans more than one sector on the DVD-RW disc. Windows XP SP2 can recognize that a DVD is using UDF, but Windows Explorer displays the contents of a DVD as an empty folder. A hotfix is available for this<ref>{{cite web |url=http://support.microsoft.com/kb/899527 |title=Windows XP UDF hotfix |publisher=microsoft.com}}</ref> and is included in Service Pack 3.<ref name="CD-ROM Drive"/>

Due to the default UDF versions and options, a UDF partition formatted by Windows cannot be written under macOS. On the other hand, a partition formatted by macOS cannot be directly written by Windows, due to the requirement of a [[Master boot record|MBR]] partition table. In addition, Linux only supports writing to UDF 2.01. A script for Linux and macOS called {{code|format-udf}} handles these incompatibilities by using UDF 2.01 and adding a fake MBR;<ref>{{cite web |title=JElchison/format-udf: Bash script to format a block device (hard drive or Flash drive) in UDF |url=https://github.com/JElchison/format-udf |website=GitHub |date=27 June 2020 |quote=The output is a drive that can be used for reading/writing across multiple operating system families: Windows, macOS, and Linux. This script should be capable of running in macOS or in Linux.}}</ref> for Windows the best solution is using the command-line tool {{code|format /FS:UDF /R:2.01}}.

Tools for repairing UDF file systems and for modifying their properties have been made for some operating systems. On Windows, the [[chkdsk]] tool is able to repair UDF file systems (if not too damaged, like any file system). A similar tool for Linux, <code>udffsck</code>, was under development by Vojtech Vladyka as an extension of [[fsck]], and it was planned to be added to the ''udftools'' package. However, it was abandoned by its developer in 2018.<ref>[https://github.com/pali/udftools/pull/7 udffsck 1.00-beta by argorain · Pull Request #7 · pali/udftools · GitHub]</ref> 

A tool for toggling the write protection flag, <code>udftune</code>, was under development by Johannes Truschnigg in 2023 but could not be merged into the main ''udftools'' package because its maintainer Pali Rohár has reportedly lost access to his GitHub account.<ref name=pali-github>[https://github.com/pali/udftools/pull/63#issuecomment-1889687420 udftune: Add initial implementation by jtru · Pull Request #63 · pali/udftools · GitHub (comment 1889687420 on January 12, 2024)]</ref>

{| class="wikitable sortable"
|+ Table of operating systems
| colspan=10 | 
* Unless otherwise noted, read and write support means that only the plain UDF build is supported, but not the VAT and spared build.
* Support for "read" means that a UDF formatted disk can be mounted by the system. It enables the user to read files from the UDF volume using the same interface that is used to access files on other disks connected to the computer.
* Support for "write" means that, in addition to reading files from a mounted UDF volume, data such as files can be modified, added, or deleted.
|-
!
! colspan="5" | UDF revision (read + write)
! colspan="2" | Non-plain
!
|-
! Operating system
! 1.02
! 1.50
! 2.0x
! 2.50
! 2.60
! VAT
! Sparing tables
! Note
|-
| [[AIX (operating system)|AIX]] 5.2, 5.3, 6.1
|
| {{yes}}
| {{yes}}
| {{no}}
| {{no}}
|
|
| 1.5 is default<ref>{{cite web |url=http://publib.boulder.ibm.com/infocenter/aix/v6r1/index.jsp |title=Welcome to the AIX 6.1 Information Center |publisher=IBM |access-date=25 September 2010}}</ref>
|-
| [[AmigaOS]] 4.0
| {{yes}}
| {{yes}}
|
|
|
|
|
|
|-
| [[BeOS]]/[[magnussoft ZETA]]/[[Haiku (operating system)|Haiku]]
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
|
|
|
|-
| [[OS/2]] (including [[eComStation]] and [[ArcaOS]])
|
|
| {{yes}}
|
|
|
|
| Additional fee drivers on OS/2.
|-
| [[FreeBSD]] 5.0 and newer
| {{partial|read only}}
| {{partial|read only}}<ref>{{cite web |title=FreeBSD 5.0-RELEASE Release Notes |url=https://www.freebsd.org/releases/5.0R/relnotes-i386.html#AEN1150}}</ref>
| {{no}}
| {{no}}
| {{no}}
| {{no}}
| {{yes}}
|
|-
| [[Linux kernel]] 2.2
| {{no}}
| {{no}}
| {{no}}
| {{no}}
| {{no}}
| {{no}}
| {{no}}
|
|-
| [[Linux kernel]] 2.4
| {{yes}}
| {{yes}}
| {{yes}}{{efn|name="linux24"|Linux version 2.3.17–2.4.5 supports only UDF revision up to 2.00, Linux version 2.4.6 and newer supports also UDF revision 2.01.}}
| {{no}}
| {{no}}
| {{yes}}
| {{yes}}
|
|-
| [[Linux kernel]] 2.6.0–2.6.25
| {{yes}}
| {{yes}}
| {{yes}}
| {{no}}
| {{no}}
| {{yes}}
| {{yes}}
| Kernel versions prior to 2.6.10 supported fewer media types.
|-
| [[Linux kernel]] 2.6.26 and newer
| {{yes}}
| {{yes}}
| {{yes}}
| {{partial|read only}}<ref name="linuxsrc">{{cite web
    | title = Linux 3.13: fs/udf/udf_sb.h
    | url = https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/fs/udf/udf_sb.h?id=v3.13#n11
    | date = 2013-09-24
    | access-date = 2014-01-29}}</ref>
| {{partial|read only}}<ref name=udf260p/>{{rp|10}}
| {{yes}}
| {{yes}}
| Permission-related mounting options added in 2.6.30.<ref>{{cite web
    | title = Linux 2.6.30 Changelog
    | url = http://kernelnewbies.org/Linux_2_6_30
    | date = 2009-06-12
    | access-date = 2015-09-13}}</ref> Auto-detection of UDF file system on hard disk is supported since version 2.6.30. Auto-detection of UDF file system on disk images was fixed in 4.11.
|-
| [[Mac OS 8#Mac OS 8.1|Mac OS 8.1]]–[[Mac OS 8#Mac OS 8.5|8.5]]
| {{yes}}
| {{no}}
| {{no}}
| {{no}}
| {{no}}
| {{no}}
| {{no}}
| Some earlier versions of Mac OS, such as [[System 7|7.5, 7.6]], and 8.0 are also supported via third-party utilities, along with additional UDF version support for 8.1 and 8.5.{{efn|name="MacOSExtraUDF"|Read and (depending on which utility is used) write support for UDF versions 1.02, 1.50, 2.00, and 2.01 (support for 1.50 is not natively present in 8.1 or 8.5, and 2.00 onwards was not supported by the classic Mac OS at all) on optical disks available with third party utilities such as [[Adaptec]]'s UDF Volume Access or Software Architects' DVD-RAM Tune-Up utilities.}}
|-
| [[Mac OS 8#Mac OS 8.6|Mac OS 8.6]], [[Mac OS 9]]
| {{yes}}
| {{yes}}
| {{no}}
| {{no}}
| {{no}}
| {{no}}
| {{no}}
| Additional UDF version support via third-party utilities.{{efn|name="MacOSExtraUDF"}}
|-
| [[Mac OS X]] 10.0–10.3
| {{yes}}
| {{yes}}<ref name="macmount103">{{cite web |title=mount_udf manpage for Mac OS X 10.3 |url=http://www.manpagez.com/man/8/mount_udf/osx-10.3.php |quote=UDF 1.50 is supported. UDF 2.0 and later is not.}}</ref>
| {{no}}<ref name="macmount103" />
| {{no}}
| {{no}}
| {{no}}
| {{no}}
|
|-
| [[Mac OS X]] 10.4
| {{yes}}
| {{yes}}
| {{yes}}
| {{no}}{{efn|Support via third party utility [[Roxio Toast|Toast]] 9+ [http://www.roxio.com/enu/products/toast9/plugin/overview.html HD Plugin]}}<ref name="macrec" />
| {{no}}{{efn|Support via third party utility Toast 9+}}
| {{no}}
| {{yes}}{{efn|Since version 10.4.11}}
| Can create UDF 1.50 (plain build) volumes using the <code>drutil</code> utility.
|-
| Mac OS X 10.5 and newer
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}<ref name="macmount105">{{cite web |title=mount_udf manpage for Mac OS X 10.5 |url=http://www.manpagez.com/man/8/mount_udf/osx-10.5.php |quote=Reading of all UDF revisions (1.02–2.60) on both block device (e.g. hard drives and USB drives) and most optical media is supported. Writing to block devices, DVD-RW and DVD+RW is supported with the following exceptions: (1) Cannot write Finder Info, Resource Fork, or other extended attributes in UDF volumes of revision 1.02 and 1.50; (2) Cannot write to mirrored metadata partition.}}</ref><ref name="macrec">{{cite web |title=Disc Recording Release Notes for OS X v10.5 |url=https://developer.apple.com/library/content/releasenotes/MusicAudio/RN-DiscRecording/index.html |quote=This release note describes changes to the Disc Recording frameworks from OS X version 10.4. The Disc Recording content creation engine now supports writing UDF 2.0 discs in addition to UDF 1.02 and 1.5.}}</ref>
| {{partial|read only}}<ref name="macmount105" /><ref name="mactech">{{cite web |title=Mac Technology Overview – Kernel and Device Drivers Layer |url=https://developer.apple.com/library/content/documentation/MacOSX/Conceptual/OSX_Technology_Overview/SystemTechnology/SystemTechnology.html |quote=OS X supports reading UDF revisions 1.02 through 2.60 on both block devices and most optical media, and it supports writing to block devices and to DVD-RW and DVD+RW media using UDF 2.00 through 2.50 (except for mirrored metadata partitions in 2.50).}}</ref>
| {{yes}}
| {{yes}}
| To create, use <code>newfs_udf</code> utility.
|-
| [[NetBSD]] 4.0
| {{partial|read only}}<ref>{{cite web |url=https://www.netbsd.org/releases/formal-4/NetBSD-4.0.html |title=Announcing NetBSD 4.0 |quote=Added UDF support for optical media and block devices, see mount_udf(8). Read-only for now.}}</ref>
| {{partial|read only}}
| {{partial|read only}}
| {{partial|read only}}
| {{partial|read only}}
| {{yes}}
| {{yes}}
| Reading multi-session VAT, spared and metapartition variants<br> from all CD, DVD and BD variants as well as HDD and Flash media.
|-
| [[NetBSD]] 5.0
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
| Write support for all builds and media including multi-session VAT.<ref>{{cite web |url=http://www.netbsd.org/releases/formal-5/NetBSD-5.0.html |title=NetBsd 5 release notes |publisher=NetBSD}}</ref> Create new with <code>newfs_udf</code>.<br>Limited writing on 2.50/2.60 (due to needing pre-allocated, fixed sized metadata partition).<ref>{{cite web |url=http://netbsd.gw.com/cgi-bin/man-cgi?mount_udf+8+NetBSD-5.0 |title=NetBSD System Manager's Manual |access-date=25 September 2010}}</ref>
|-
| [[NetWare]] 5.1
|
|
|
|
|
|
|
|
|-
| NetWare 6
|
|
|
|
|
|
|
|
|-
| [[OpenBSD]] 3.8–3.9
| {{partial|read only}}<ref>{{cite web |url=https://www.openbsd.org/38.html|title=OpenBSD 3.8}}</ref>
| {{no}}
| {{no}}
| {{no}}
| {{no}}
| {{no}}
| {{no}}
|
|-
| [[OpenBSD]] 4.0–4.6
| {{partial|read only}}
| {{partial|read only}}<ref name="openbsd40">{{cite web |url=https://www.openbsd.org/40.html |title=OpenBSD 4.0}}</ref>
| {{no}}
| {{no}}
| {{no}}
| {{yes}}<ref name="openbsd40" />
| {{no}}
|
|- 
| [[OpenBSD]] 4.7
| {{partial|read only}}
| {{partial|read only}}
| {{partial|read only}}
| {{partial|read only}}<ref name="openbsd47">{{cite web |url=http://www.openbsd.org/47.html |title=The OpenBSD 4.7 Release |publisher=OpenBSD |access-date=25 September 2010}}
</ref>
| {{partial|read only}}<ref name="openbsd47"/>
| {{yes}}
| {{yes}}
|
|- 
| [[Solaris (operating system)|Solaris]] 7 11/99+
| {{yes}}
| {{yes}}
|
|
|
|
|
|
|-
| Solaris 8/9/10
| {{yes}}
| {{yes}}
|
|
|
|
|
|
|-
| [[DOS]], [[FreeDOS]], [[Windows 3.11]], [[Windows 95]], [[Windows 95#Editions|Windows 95 OSR2+]] and other DOS based OS
| {{no}}<ref name="msfscc">{{cite web |url=https://msdn.microsoft.com/en-us/library/cc232128.aspx |title=[MS-FSCC]: File System Control Codes: 6 Appendix B: Product Behavior|date=27 April 2022 }} Windows UDF File System Support table</ref>
| {{no}}
| {{no}}
| {{no}}
| {{no}}
| {{no}}
| {{no}}
| No native support. Filesystems that have an [[ISO9660]] backward compatibility structure can be read.
|-
| [[Windows 98]], [[Windows Me]]
| {{partial|read only and only for CD/DVD optical disks}}<ref>{{cite book|author=Microsoft Corporation|title=Microsoft Windows 98 Resource Kit|date=January 1998|publisher=Microsoft Press|isbn=978-1-57231-644-7|page=[https://archive.org/details/isbn_9781572316447/page/442 442]|chapter=Chapter 10 – Disks and File Systems|url=https://archive.org/details/isbn_9781572316447/page/442|access-date=9 September 2017|quote=Windows 98 has a new read-only Universal Disk Format (UDF) system, which supports reading media formatted according to UDF specification 1.02.}}</ref><ref>{{cite book|author=Microsoft Corporation|title=Microsoft Windows 98 Resource Kit|date=January 1998|publisher=Microsoft Press|isbn=978-1-57231-644-7|page=[https://archive.org/details/isbn_9781572316447/page/1316 1316]|chapter=Chapter 28 – Windows 98 Architecture|url=https://archive.org/details/isbn_9781572316447/page/1316|access-date=9 September 2017|quote=The 32-bit, protected-mode UDF file system in Windows 98 is implemented according to Revision 1.02 of Universal Disk Format Specification by Optical Storage Technology Association (OSTA). It provides read-only access to UDF-formatted media, such as DVD discs. The UDF file system uses VCACHE and is dynamic, requiring no configuration or static allocation on the part of the user.}}</ref><ref name="nt5dll">{{cite web |url=https://www.microsoft.com/msj/1197/nt5dll.aspx|title=A Programmer's Perspective on New System DLL Features in Windows NT 5.0, Part I |author=Matt Pietrek|date=November 1997|publisher=Microsoft Systems Journal |access-date=9 September 2017 |quote=Windows NT 5.0 also adds UDF (Universal Disk Format). ... The UDF implementations shipping in both Windows 98 (UDF 1.02) and Windows NT 5.0 (UDF 1.50) are read-only.|author-link=Matt Pietrek }}</ref><ref name="msfscc" />
| {{no}}
| {{no}}
| {{no}}
| {{no}}
| {{no}}
| {{no}}
| Additional read/write support via third party utilities{{efn|name="win3rd"|Read and write support for other UDF versions on optical disks available with third party utilities such as [[Drive Letter Access|DLA]], [[InCD]] or Toshiba/Panasonic/Matsushita UDF 2.5 driver. Read and write support for removable disks and hard disks available with third party utilities such as SAI's WriteUDF!.}}
|-
| [[Windows 2000]]
| {{partial|read only}}<ref name="nt5dll" /><ref name="inside2000">{{cite book|last1=Russinovich|first1=M. E.|last2=Solomon|first2=D. A.|title=Inside Microsoft Windows 2000|chapter-url=https://archive.org/details/insidemicrosoftw0000solo|chapter-url-access=registration|edition=Third|year=2000|publisher=Microsoft Press|location=Redmond, Washington|isbn=978-0-7356-1021-7|chapter=Chapter 12 – File Systems|quote=The Windows 2000 UDF file system implementation is ISO 13346-compliant and supports UDF versions 1.02 and 1.5. ... the Windows 2000 UDF driver (Udfs.sys) provides read-only support.}}</ref><ref name="winint4">{{cite book|last1=Russinovich|first1=M. E.|last2=Solomon|first2=D. A.|title=Microsoft Windows Internals, Fourth Edition: Microsoft Windows Server 2003, Windows XP, and Windows 2000|url=https://books.google.com/books?id=I2vjPx-6qK0C|edition=Fourth|year=2005|publisher=Microsoft Press|location=Redmond, Washington|isbn=0-7356-1917-4|page=691|chapter=Chapter 12 – File Systems|quote=The UDF driver supports UDF versions 1.02, version 1.5 on Windows 2000, and versions 2.0 and 2.01 on Windows XP and Windows Server 2003. ... the Windows UDF driver (Udfs.sys) provides read-only support. Windows does not implement support for other UDF features, including named streams, access control lists, or extended attributes.}}</ref><ref name="locfswin">{{cite report|id=WinHEC 2004 Version|date=May 5, 2004|section-url=http://download.microsoft.com/download/5/b/5/5b5bec17-ea71-4653-9539-204a672f11cf/locfilesys.doc|title=Local File Systems for Windows|publisher=Microsoft Corporation|pages=6–8|chapter=2.3 About the UDF File System|chapter-format=doc}}</ref><ref name="msfscc" />
| {{partial|read only}}
| {{no}}
| {{no}}
| {{no}}
| {{no}}
| {{no}}
| Additional read/write support via third party utilities{{efn|name="win3rd"}}
|-
| [[Windows XP]]/[[Windows Server 2003|Server 2003]]
| {{partial|read only}}<ref name="winint4" /><ref name="locfswin" /><ref name="msfscc" />
| {{partial|read only}}
| {{partial|read only}}
| {{no}}
| {{no}}
| {{yes}}
| {{yes}}{{efn|Service Pack 3 required}}
| Additional read/write support via third party utilities{{efn|name="win3rd"}}
|-
| [[Windows Vista]]
| {{yes}}<ref name="winint5">{{cite book|last1=Russinovich|first1=M. E.|last2=Solomon|first2=D. A.|last3=Ionescu|first3=A.|title=Windows Internals, 5th Edition: Windows Vista and Windows Server 2008|edition=5th|year=2009|publisher=Microsoft Press|location=Redmond, Washington|isbn=978-0-7356-3796-2
|page=981|chapter=Chapter 12 – File Systems|url=https://books.google.com/books?id=VgjAQjsc6g8C|quote=The UDF driver supports UDF versions up to 2.60. The Windows UDF driver (Udfs.sys) provides read-write support ... when using UDF 2.50 and read-only support when using UDF 2.60. However, Windows does not implement support for certain UDF features such as named streams and access control lists.}}</ref><ref name="winint6">{{cite book |last1=Russinovich |first1=M. E.|last2=Solomon |first2=D. A. |last3=Ionescu 
|first3=A. |title=Windows Internals, Part 2, 6th Edition: Windows 7 and Windows Server 2008 R2|edition=6th |year=2012 |publisher=Microsoft Press |location=Redmond, Washington |isbn=978-0-7356-6587-3
|page=393 |chapter=Chapter 12 – File Systems |url=https://books.google.com/books?id=_Y2WiG6WfGkC|quote=The UDF driver supports UDF versions up to 2.60. The Windows UDF driver (Udfs.sys) provides read-write support ... when using UDF 2.50 and read-only support when using UDF 2.60. However, Windows does not implement support for certain UDF features such as named streams and access control lists.}}</ref><ref name="locfswin" /><ref name="msfscc" />
| {{yes}}
| {{yes}}
| {{yes}}
| {{partial|read only}}<ref name="winint5" /><ref name="winint6" /><ref name="locfswin" /><ref name="msfscc" />
| {{yes}}
| {{yes}}
| Referred to by Microsoft as [[Live File System]]. Requires fake MBR partition on non-optical devices.
|-
| [[Windows 7]] and newer
| {{yes}}<ref name="msfscc" />
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
| 
|-
! Operating system
! 1.02
! 1.50
! 2.0x
! 2.50
! 2.60
! VAT
! Sparing tables
! Note
|-
!
! colspan="5" | UDF revision (read + write)
! colspan="2" | Non-plain
!
|}

== See also ==

* [[Comparison of file systems]]
* [[DVD authoring]]
* [[ISO/IEC 13490]]

== Notes ==
{{notelist}}

== References ==

{{reflist|30em}}

== Further reading ==

* ISO/IEC 13346 standard, also known as [http://www.ecma-international.org/publications/files/ECMA-ST/Ecma-167.pdf ECMA-167].

== External links ==
*[http://www.osta.org/ Home page of the Optical Storage Technology Association (OSTA)]
*UDF specifications: [http://www.osta.org/specs/pdf/udf102.pdf 1.02], [http://www.osta.org/specs/pdf/udf150.pdf 1.50], [http://www.osta.org/specs/pdf/udf200.pdf 2.00], [http://www.osta.org/specs/pdf/udf201.pdf 2.01], [http://www.osta.org/specs/pdf/udf250.pdf 2.50], [http://www.osta.org/specs/pdf/udf260.pdf 2.60] (March 1, 2005), [http://www.osta.org/specs/pdf/SecureUDF_1_00.pdf SecureUDF]
* [https://files.catbox.moe/h93oex.PDF UDF 1.01] ([https://pomf2.lain.la/f/sovv0v.PDF mirror], original file name: "UDF_101.PDF") – This specification was never published on the OSTA website and only existed in its early days on a FTP server that is long gone as of 2024, at [https://www.osta.org/osta/udf101w6.zip this URL] (linked from {{usurped|1=[https://web.archive.org/web/20070115073657/http://www.elprofesionaldelainformacion.com/contenidos/1996/septiembre/udf.html this 1996 article]}}).
* [https://files.catbox.moe/16jm1n.zip An archive containing all UDF specifications] (22 MB, [https://pomf2.lain.la/f/m6g1ynbb.tar mirror]<!--pomf2 does not accept ZIP files, hence TAR.-->)
* [https://files.catbox.moe/8h8dnl.zip An archive containing the UDF specifications and some ECMA documents referenced from them] (73 MB, [https://pomf2.lain.la/f/mikhvg67.tar mirror])<!-- separate archive due to much larger size -->
* [https://www.ecma-international.org:443/wp-content/uploads/ECMA-167_3rd_edition_june_1997.pdf ECMA 167/3: Volume and File Structure for Write-Once and Rewritable Media using Non-Sequential Recording for Information Interchange (June 1997)] (referenced from UDF specification)
*[http://sites.google.com/site/udfintro/ Wenguang Wang's UDF Introduction]
*[http://sourceforge.net/projects/linux-udf/ Linux UDF support]
*"[http://support.microsoft.com/kb/321640/en-us CD-ROM Drive May Not Be Able to Read a UDF-Formatted Disc in Windows XP]", Microsoft Support
*[http://publib.boulder.ibm.com/infocenter/systems/index.jsp?topic=/com.ibm.aix.baseadmn/doc/baseadmndita/cdromudfs.htm AIX – CD-ROM file system and UDFS]
*[http://web.archive.org/web/19961113064531/http://www.osta.org:80/html/ostatech.html OSTA Technology (mention of UDF 1.00 on the 1996 OSTA website)] (The UDF 1.00 specification itself is [[lost literary work]] as of 2024.)
*{{usurped|1=[http://web.archive.org/web/20070115073657/http://www.elprofesionaldelainformacion.com/contenidos/1996/septiembre/udf.html UDF – El profesional de la información (mention of UDF 1.01)]}}
* An archive of the source codes of various optical disc authoring and reading tools, including <code>udftools</code> and its forks that contain <code>udftune</code> and <code>udffsck</code>, as well as the cross-platform formatting script <code>format-udf</code>: [https://files.catbox.moe/128twp.zip ZIP (41 MB)]<!-- better compatibility -->, [https://pomf2.lain.la/f/p0xl8f9s.tbz TAR BZip2 (26 MB)]<!-- stronger compression -->.

{{Filesystem}}
{{Ecma International Standards}}
{{List of International Electrotechnical Commission standards}}

[[Category:Disk file systems]]
[[Category:ISO standards]]
[[Category:IEC standards]]
[[Category:Ecma standards]]
[[Category:Windows components]]