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{{Short description|Convention that is widely accepted but unofficial}}
{{Original research|date=April 2019}}
A '''de facto standard''' is a custom or [[Convention (norm)|convention]] that is commonly used even though its use is not required.

{{lang|la|[[De facto]]}} is a Latin phrase (literally "[[wikt:de facto|of fact]]"), here meaning "in practice but not necessarily ordained by law" or "in practice or actuality, but not officially established".

A de facto standard contrasts an [[international standard]] which is defined by an organization such as [[International Standards Organization]], or a standard required by law (also known as [[de jure standard]]s).<ref name=":0" />

Joint technical committee on information technology (ISO/IEC JTC1) developed a procedure in order for de facto standards to be processed through the formal standardization system to be transformed into international standards from [[ISO]] and [[International Electrotechnical Commission|IEC]].<ref>{{cite book |title=International standards and private standards |date=February 2010 |publisher=International Organization for Standardization |location=Geneva, Switzerland |isbn=978-92-67-10518-5 |url=https://docplayer.net/23885374-International-standards-and-private-standards.html}}</ref>

In [[social sciences]] a voluntary standard that is also a de facto standard is a typical solution to a [[coordination problem]].<ref name="Ulmann">{{cite book |author=Edna Ullmann-Margalit |authorlink=Edna Ullmann-Margalit|title=The Emergence of Norms |url=https://books.google.com/books?id=9FLCBwAAQBAJ&pg=PA94 |date=5 March 2015 |publisher=OUP Oxford |isbn=978-0-19-106458-6 |page=94}}</ref> The choice of a de facto standard tends to be stable in situations in which all parties can realize mutual gains, but only by making mutually consistent decisions. In contrast, an enforced de jure standard is a solution to the [[prisoner's dilemma]].<ref name="Ulmann" />

== Examples ==
Examples of some well known de facto standards:
* The [[drive side|driver's seat side]] in a given country often starts as a user/industry preference, turning to a local tradition, then a [[traffic code]].
* The [[QWERTY]] layout was one of several options for the layout of letters on [[typewriter]] (and later [[keyboard (computing)|keyboard]]) keys.
* [[first-mover advantage|Early entrance to the market]].<ref name=":0">{{cite book |last1=Campbell |first1=Robert |url=https://learning.oreilly.com/library/view/academic-and-professional/9781843346692/ |title=Academic and Professional Publishing |last2=Pentz |first2=Ed |last3=Borthwick |first3=Ian |publisher=Chandos Publishing |year=2012 |pages=9 |isbn=978-1-84334-669-2 }}</ref>

===File formats===

* [[Portable Document Format|PDF]] was first created in 1993 by [[Adobe Systems|Adobe]]. Adobe internal standards were part of its [[software quality]] systems, but they were neither published nor coordinated by a standards body. With the [[Acrobat Reader]] program available for free, and continued support of the format, PDF eventually became the de facto standard for printable documents. In 2005, [[PDF/A]] became a [[de jure standard]] as [[International Organization for Standardization|ISO]] 19005-1:2005.<ref>{{cite web |title=ISO 19005-1:2005 – Document management – Electronic document file format for long-term preservation – Part 1: Use of PDF 1.4 (PDF/A-1) |url=http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=38920 |access-date=17 April 2015}}</ref> In 2008 Adobe's PDF 1.7 became [[International Organization for Standardization|ISO]] 32000-1:2008.<ref>{{cite web |title=ISO 32000-1:2008 – Document management – Portable document format – Part 1: PDF 1.7 |url=http://www.iso.org/iso/catalogue_detail.htm?csnumber=51502 |access-date=17 April 2015}}</ref><ref>{{cite web |title=Adobe – Release PDF for Industry Standardization FAQ |url=https://www.adobe.com/pdf/release_pdf_faq.html |access-date=17 April 2015}}</ref>
* [[AutoCAD DXF]], an [[ASCII]] format for import and export of [[Computer-aided design|CAD]] drawings and fragments in the 1980s and 1990s. In the 2000s, [[XML]]-based standards emerged as de facto standards.
* The [[MP3]] audio format started as an alternative to [[WAV]] for internet music distribution, then replaced it. It is now supported by the vast majority of music players, [[Portable media player|audio transport]], [[Media server|audio storage]], and non-commercial media.
* [[Microsoft Word]] [[DOC (computing)|DOC]]. Due to the market dominance of Word, it is supported by all office applications that intend to compete with it, typically by [[reverse engineering]] the undocumented file format. Microsoft has repeatedly internally changed the file specification between versions of Word to suit their own needs, while continuing to reuse the same file extension identifier for different versions.
* [[FITS]] and [[Comma-separated values|CSV]] file formats, commonly used in science and engineering, with FITS traditionally used in [[astronomy]].

===Connectors and interconnect standards===
{{Unreferenced|section|date=December 2025}}
* [[Phone connector (audio)|Phone connector]] (3.5 mm jack), [[RCA connector|RCA]] and [[XLR connector|XLR]] connectors, used in the audio industry for connecting audio equipment such as headphones, mixing desks, microphones, stage lighting, etc.
* [[MIDI]] connection (using [[DIN connector]] or phone connector), electrical and protocol standard for connecting musical instruments, synthesizers, drum machines, sequencers, and some audio equipment.
* [[DMX512]] (commonly just DMX) with [[XLR connector]] to control and sometimes power stage and venue lights, effects, smoke machines, laser projectors, and pyrotechnics.
* [[PCI Express]] electrical and mechanical interface, and interconnect protocol used in computers, servers, and industrial applications.
* [[GPIB]], multi-device bus protocol, mechanical and electronic interface commonly found in electronic test equipment, e.g. digital [[multimeter]]s, [[oscilloscope]]s, etc. Initially created by Hewlett [[Hewlett-Packard]] as HP-IP. Commonly used with [[SCPI]] protocol.
* [[HDMI]], [[Display Port]], [[VGA]] for video, [[RS-232]] for low-bandwidth serial communication.
* [[USB]] for high-speed serial interface in computers and for powering or charging low-power external devices (like mobile phones, headphones, portable hard drives) usually using micro USB plug and socket.
* [[BNC connector|BNC]] for medium-frequency signal in electronic engineering testing (commonly used by signal generators, oscilloscopes, multimeters, etc.) and sometimes in video-signal delivery between devices in studios and other professional settings.
* [[AMP Incorporated|AMP]]'s AMP MATE-N-LOK / [[Molex connector|Molex]]'s Standard 0.093" Pin Power plug and socket, commonly used on hard drives, and other medium-power devices both in PC, server, industrial applications, and others where standardized power connector for 5 V and 12 V is required, and off-the-shelf [[Power supply unit|PSU]] can be used. In embedded applications it is usually replaced with smaller square connector, which is easier to connect.
* 2.54 mm (0.1 inch) pin spacing on many electronic components, including [[Dual in-line package|DIP]], [[Dual in-line package#Single in-line|SIL]] packages, [[header connector]]s, and many more. The standard spacing enable use of these devices in prototyping boards and standardized sockets.
* [[4–20 mA]] current loop, used in industrial control and automation.
* 3.5-inch and 2.5-inch hard drives.
* [[19-inch rack]] standards for telecommunication, server, storage, audio, music, video, and power equipment.
* [[ATX]] motherboard, back plane, and power standards.

===Materials and units of packaging===

* [[Solder]]ing alloys in electronics, like {{chem2|Sn60Pb40}}.
* [[Aluminium alloy]]s, such as [[6061 aluminium alloy|6061]].
* [[Intermodal container|Intermodal]] 48-foot container.

===Miscellaneous===

* Many American-made [[spark plugs]] require a {{frac|13|16}}-inch hex socket (21 mm) to remove or install.
* The 1/2 inch (12.7 mm) spacing of the rollers in a [[bicycle chain]].
* The [[IBM Personal Computer]] (PC). By one year after its 1981 release, [[John Dvorak]] described the PC as rapidly becoming a "de facto standard microcomputer".<ref name="zussman19820823">{{cite news |url=https://books.google.com/books?id=VDAEAAAAMBAJ&pg=PA29 |title=Let's keep those systems open |work=InfoWorld |date=1982-08-23 |access-date=29 January 2015 |author=Zussman, John Unger |pages=29}}</ref> With the [[MS-DOS]] and [[Microsoft Windows]] [[operating system]]s, it gained a large share of the personal-computer market. Because of the great [[influence of the IBM PC on the personal computer market]], competing products like the [[Rainbow 100]] were eventually withdrawn.
* Programming languages that have multiple implementations such as [[PHP]] tend to also have a de facto standard. In PHP's case the de facto standard is the binaries available from php.net, rather than the [[Phalanger (compiler)|Phalanger]] implementation.
* Use of programming languages [[R (programming language)|R]] and [[Python (programming language)|Python]] in science and engineering disciplines, other than computer science, where automated analysis of data is required, while remaining simple enough for a non-professional.
* [[TeX]] typesetting system, commonly used in creating scientific articles and reports for publication (in fact many journals require the publication to be fully written in TeX).<ref>{{cite journal |last=Beebe |first=Nelson H. F. |date=2003 |title=25 Years of TEX and METAFONT: Looking Back and Looking Forward |url=https://tug.org/TUGboat/Articles/tb25-1/beebe-2003keynote.pdf |journal=TUGboat |pages=10}}</ref>

=== Legal adulthood age ===
In the vast majority of countries, the [[age of majority]] is defined as 18 years or older. Very few countries or regions set the lower limit of adulthood higher or lower than 18 years of age. Furthermore, since the UN [[Convention on the Rights of the Child]] defines a child as anyone under 18 years of age, the ''de facto'' internationally recognised age of adulthood is 18 years or older.

== Standardization disputes ==
{{Unreferenced|section|date=December 2025}}
There are many examples of de facto consolidation of a standard by market forces and competition, in a [[two-sided market]], after a [[format war|dispute]]. Examples:
* [[Alternating current]] and [[direct current]] in the [[war of the currents]].
* [[VHS]] over [[Betamax]] in the [[videotape format war]].
* [[Blu-ray]] and [[HD DVD]] during the [[high-definition optical disc format war]].
* [[Scalable Vector Graphics]] (SVG) over [[Adobe Flash]] for [[vector graphics]] web-page animations.

An example of an ongoing dispute is [[OASIS (organization)|OASIS]]'s [[OpenDocument]] format vs Microsoft's [[Office Open XML]] format.{{Citation needed|date=May 2024}}

== See also ==
* [[Platform evangelism]]
* [[Appeal to tradition]]
* [[Dominant design]]
* [[Embrace, extend, and extinguish]]
* [[Harmonization (standards)]]
* [[Monopoly]]
* [[Protocol ossification]]
* [[Specification (technical standard)|Specification]]
* [[Standardization]]
* [[Technical standard]]

== References ==
{{reflist}}

[[Category:Broad-concept articles]]
[[Category:Technological change]]
[[Category:Standards]]

De facto standard - Revision history

RS-485: Imported from Wikipedia (overwrite)