A de facto standard is a custom, convention, product, or system that has achieved a dominant position by public acceptance or market forces (such as early entrance to the market). De facto is a Latin phrase meaning "concerning the fact" or "in practice".

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 is the better choice for 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:

Examples of long-time de facto but never de jure standards (for computer file formats):

De facto (English pronunciation: /diː ˈfæktoʊ/, /deɪ/,Latin pronunciation: [deː ˈfaktoː]) is a Latin expression that means "concerning fact." In law, it often means "in practice but not necessarily ordained by law" or "in practice or actuality, but not officially established." It is commonly used in contrast to de jure (which means "concerning the law") when referring to matters of law, governance, or technique (such as standards) that are found in the common experience as created or developed without or contrary to a regulation. When discussing a legal situation, de jure designates what the law says, while de facto designates action of what happens in practice. It is analogous and similar to the expressions "for all intents and purposes" or "in fact". The term can also be used in the context of conducting activity as a "matter of course" e.g. copying an individual on an email de facto.

'De facto' racial discrimination and segregation in the USA during the 1950s and 1960s was simply discrimination that was not segregation by law (de jure).

Robert Bruce "Rob" Ford (born May 28, 1969) is a Canadian politician and businessman. He is the 64th and current Mayor of Toronto, Ontario, Canada. He was first elected to city council in the 2000 Toronto municipal election, and was re-elected to his council seat in 2003 and again in 2006. Ford was elected Mayor in the 2010 mayoral election, and took office on December 1 of that year. Ford's father Doug Ford, Sr. was also a politician and his brother Doug is a Toronto city councillor.

Born in Etobicoke, Ford is the youngest of four children of Diane and Doug Ford, Sr.. Ford Sr. was the founder of DECO Labels and Tags, which makes pressure-sensitive labels for plastic-wrapped grocery products at an estimated $100 million in annual sales. Ford Sr. later became a Member of the Ontario Legislature in the Progressive Conservative government of Mike Harris. Not long after Rob Ford's birth in 1969, the success of the family business allowed the family to build a six-bedroom home in Etobicoke, which has a full-sized swimming pool and gardens that can host nearly a thousand visitors.

John Anthony Frusciante ⁱ/fruːˈʃɑːnteɪ/; born March 5, 1970) is an American guitarist, singer, songwriter, record and film producer. He is best known as the former guitarist of the rock band Red Hot Chili Peppers, with whom he had been for a number of years and recorded five studio albums. Frusciante has an active solo career, having released ten albums under his own name, as well as two with Josh Klinghoffer and Joe Lally as Ataxia. His solo recordings include elements ranging from experimental rock and ambient music to New Wave and electronica. Influenced by guitarists of various genres, Frusciante emphasizes melody and emotion in his guitar playing, and favors vintage guitars and analog recording techniques.

Frusciante joined the Red Hot Chili Peppers at eighteen years old, first appearing on the band's 1989 album, Mother's Milk. The group's follow-up album, Blood Sugar Sex Magik (1991), was a breakthrough success. However, he was overwhelmed by the band's new popularity and quit in 1992. He became a recluse and entered a long period of drug addiction, during which he released his first solo recordings: Niandra Lades and Usually Just a T-Shirt (1994) and then Smile from the Streets You Hold (1997). In 1998, he successfully completed drug rehabilitation and rejoined the Red Hot Chili Peppers with the album Californication (1999). His album To Record Only Water for Ten Days was made in 2001. On a creative spree, Frusciante released six solo albums in 2004; each album explored different recording techniques and genres. In 2009, Frusciante released The Empyrean and again parted ways with the Red Hot Chili Peppers. As of 2011, Frusciante is currently working on his eleventh solo album. Frusciante has produced and/or recorded with the Wu-Tang Clan, The Mars Volta, George Clinton and others. His most recent solo releases will be a 5 song EP entitled Letur-Lefr, due out in July 2012, and a full length album entitled PBX Funicular Intaglio Zone, due out in late 2012.