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A de facto standard is a custom or convention that has achieved a dominant position by public acceptance or market forces (for example, by early entrance to the market). De facto is a Latin phrase that means in fact (literally by or from fact) in the sense of "in practice but not necessarily ordained by law" or "in practice or actuality, but not officially established", as opposed to de jure.
The term de facto standard is used in contrast with obligatory standards (also known as "de jure standards"); or to express the dominant voluntary standard, when there is more than one standard available for the same use.
In social sciences, a voluntary standard that is also a de facto standard is a typical solution to a coordination problem. 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 problem.
A selection of well-known and illustrative examples of de facto and de jure standards are:
- with consolidation by tradition of use:
- The driver's seat side in a given country starts as a user/industry preference, turning to a local tradition, then a traffic code local norm.
- The QWERTY system was one of several options for the layout of letters on typewriter (and later keyboard) keys. It was developed to prevent adjacent keys from jamming on early and later mechanical typewriters, often attributed to the typist's speed. It became a de facto standard because it was used on the most commercially successful early typewriters and is now used on devices which have no moving parts such as touchscreens.
- 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, audio transport, audio storage and noncommercial media. WAV and MP3 are also "de jure ISO formats".
- with consolidation by uniqueness and efficiency:
- HTML (computer file format) started as "de facto" (1993-1995) and became the "de jure" standard (1995–present day).
- PDF (computer file format) was first created in 1993 by 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 ISO 19005-1:2005. In 2008 Adobe's PDF 1.7 became ISO 32000-1:2008.
Examples of long-time de facto but never de jure standards (for computer file formats):
- AutoCAD DXF: a de facto ASCII format for import and export of CAD drawings and fragments in the 1980s and 1990s. In the 2000s, XML based standards emerged as de facto standards.
- Microsoft Word DOC (over all other old PC word processors): one of the best known de facto standards. 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 CSV file formats, commonly used in science and engineering, with FITS traditionally used in astronomy.
- 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).
- Most American-made spark plugs require a 13⁄16-inch hex socket (21mm) to remove or install.
- The 1⁄2-inch (13 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". With the MS-DOS and Microsoft Windows operating systems, 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.
- Interpreted programming languages such as PHP that have multiple implementations 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 implementation for example.
- Use of programming languages R and Python in data science and other science disciplines, other than computer science, where automated analysis of data is required, without system being too complicated for a persons not being professionals.
Various connectors and interconnect standards - despite being formalized and standardized, almost no product is required by law or other legal standard to use them. Examples:
- Phone connector (3.5mm jack), RCA and XLR connectors, used in audio industry, for connecting audio equipment, headphones, mixing consoles, microphones (often with phantom power with 48 volts in most applications), stage lighting, etc.
- MIDI connection (using so called DIN connector), electrical and protocol standard for connecting musical instruments, synthesizers, drum machines, sequencers and some audio equipment, as well daisy chaining them.
- DMX512 (commonly just DMX) with XLR connector to control and sometimes power stage and venue lights, effects, smoke machines, laser projectors and sometimes pyrotechnics.
- PCI Express electrical and mechanical interface, and interconnect protocol used in PC computers, desktops, laptops, server, and industrial applications.
- GPIB, also known as IEEE-488, multi-device bus protocol, mechanical and electronic interface commonly found in electronic test equipment, i.e. digital multimeters, oscilloscopes, 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.
- Banana plugs in low frequency voltage and current measurements.
- BNC for medium frequency signal in electronic engineering testing (commonly used by signal generators, oscilloscopes, advanced multimeters and LCR meters, vector network analysers) and sometimes in video signal (analog and digital) delivery between devices in studios and other professional settings.
- AMP's AMP MATE-N-LOK / Molex's Standard .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 5V and 12V is required, and off the shelf PSU can be used. In embedded applications it is usually replaced with smaller square connector, that is easier to connect.
- 2.54mm (0.1 inch) pin spacing on many electronic components, including DIP, SIL packages, header connectors, and many more. The standard spacing enable use of these devices in prototyping boards and standardized sockets.
- 4-20mA current loop standard used by sensors, transducers, amplifiers, transmission lines, control and measurement equipment.
- 3.5 inch and 2.5 inch (actual dimensions are different) hard drive standard sizes.
- 19-inch rack standards for telecommunication, server, storage, audio, music, video and power equipment.
- ATX motherboard, back plane and power standards (but the intention of ATX design was to reduce number of standards, so it was not established by convention, but by biggest PC hardware and components manufacturers at the time).
- many more connectors and cables, like standardized ribbon cables medium speed and power connection between boards and devices; use of RJ45 jack in Ethernet switches for management purposes (instead of another de facto standard, RS-232 connector); SD and microSD cards for removable storage in mobile applications like photo cameras, video recorders, phones; AA batteries.
Materials and units of packaging:
- Soldering alloys in electronics, like Sn60Pb40.
- Aluminium alloys, with most common being 6061.
- Volumes, weights and quantities of common consumables usually follow round number of base legal units, i.e. in Europe milk is usually sold in 1 liter containers, and eggs are sold as quantity of 6.
- Intermodal 48-foot container.
- Alternating current over direct current: see War of the currents.
- VHS over Betamax (see videotape format war): when the VHS format for videotape recording was introduced, other recording formats were already available in the market. Regardless of whether Betamax was superior from a technical point of view or not, the VHS format won the format war due to superior marketing tactics by its proponents. The market could not support two competing formats; VHS became the de facto standard and Betamax was eventually withdrawn.
- Blu-ray over HD DVD (see high definition optical disc format war).
- Scalable Vector Graphics (SVG) over Adobe Flash (ceasing development in 2020) for vector graphics web page animations.
Examples of standards that are "in dispute" for turns de facto:
- OASIS's OpenDocument format (a de facto standard for Linux users (Apache OpenOffice, LibreOffice, Calligra, KOffice et al. use it as default file format)) vs Microsoft's Office Open XML format (a de facto standard for MS-Windows and Mac users).
- Dominant design
- Free market
- Format war
- Real versus nominal value
- Embrace, extend, and extinguish
- Edna Ullmann-Margalit (5 March 2015). The Emergence of Norms. OUP Oxford. p. 94. ISBN 978-0-19-106458-6.
- "ISO 19005-1:2005 - Document management -- Electronic document file format for long-term preservation -- Part 1: Use of PDF 1.4 (PDF/A-1)". Retrieved 17 April 2015.
- "ISO 32000-1:2008 - Document management -- Portable document format -- Part 1: PDF 1.7". Retrieved 17 April 2015.
- "Adobe - Release PDF for Industry Standardization FAQ". Retrieved 17 April 2015.
- Zussman, John Unger (1982-08-23). "Let's keep those systems open". InfoWorld. p. 29. Retrieved 29 January 2015.