A miniseries is distinguished from a soap opera or an ongoing television series, which do not usually have a predetermined number of episodes and may continue for several years. Before the term was coined in the USA in the early 1970s, the ongoing episodic form was always called a "serial", just as a novel appearing in episodes in successive editions of magazines or newspapers is called a serial. In Britain, miniseries are often still referred to as serials (such as Rock Follies).
Several commentators have offered more precise definitions of the term. In Halliwell's Television Companion, Leslie Halliwell and Philip Purser argue that miniseries tend to "appear in four to six episodes of various lengths", whilst Stuart Cunningham in Textual Innovation in the Australian Historical Mini-series defines a miniseries as, "a limited run program of more than two and less than the 13-part season or half season block associated with serial or series programming." In Television: A History, Francis Wheen states, "Both soap operas and primetime series cannot afford to allow their leading characters to develop, since the shows are made with the intention of running indefinitely. In a miniseries on the other hand, there is a clearly defined beginning, middle, and end (as in a conventional play or novel), enabling characters to change, mature, or die as the serial proceeds."
According to Francis Wheen, it was the American success in 1969–1970 of the British 26-episode serial The Forsyte Saga (1967) that made US TV executives realize that finite stories based on novels could be popular and could provide a boost to weekly viewing figures. In North America the form began in the spring of 1974 with the CBC's eight-part serial The National Dream, based on Pierre Berton's novel, and ABC's three-part QB VII, based on the novel by Leon Uris. Following these initial forays, broadcasters used miniseries to bring other books to the screen. Rich Man, Poor Man, based on the novel by Irwin Shaw, was broadcast in 12 one-hour episodes in 1976 by ABC. Alex Haley's Roots in 1977 can fairly be called the first blockbuster success of the format. Its success in the USA was partly due to its schedule: the 12-hour duration was split into eight episodes broadcast on consecutive nights, resulting in a finale with a 71 percent share of the audience and 130 million viewers, which at the time was the highest rated TV program of all time. TV Guide (April 11–17, 1987) called 1977's Jesus of Nazareth "the best miniseries of all time" and "unparalleled television".
Miniseries were popular through the 1990s on the Big Three television networks, often as big-budget ratings-grabbing efforts scheduled for sweeps months; however, the use of the format declined quickly after approximately 2000 (coinciding with a similar collapse in producing made-for-TV movies) because of budgetary concerns. The format has made somewhat of a comeback on cable; History, for example, has had some of its greatest successes with miniseries such as America: The Story of Us, Hatfields & McCoys and The Bible.
Broadcast and cable television networks have since aired programs that are branded as "limited series" or "event series." Several television executives interviewed by The Hollywood Reporter stated that the two aforementioned terms denote programs similar to the miniseries while others claim that the term "miniseries" has negative connotations to the public, having become associated with the melodramas that were commonly done under this format.