from
The Free On-line Dictionary of Computing (8 July 2008)
de facto standard
A widespread consensus on a particular product or {protocol}
which has not been ratified by any official {standards} body,
such as {ISO}, but which nevertheless has a large market
share.
The archetypal example of a de facto standard is the {IBM PC}
which, despite is many glaring technical deficiencies, has
gained such a large share of the {personal computer} market
that it is now popular simply because it is popular and
therefore enjoys fierce competition in pricing and software
development.
(1994-10-27)