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)