The first EPs were seven-inch vinyl records with more tracks than a normal single (typically five to nine of them). Although they shared size and speed with singles, they were a recognizably different format than the seven-inch single. Although they could be named after a lead track, they were generally given a different title.
 Examples include
The Beatles' Hits EP from 1963, and
The Troggs' Troggs Tops EP from 1966, both of which collected previously released tracks.
 The playing time was generally between 10 and 15 minutes.
 They also came in cardboard picture sleeves at a time when singles were usually issued in paper company sleeves. EPs tended to be album samplers or collections of singles. EPs of all original material began to appear in the 1950s. Examples are Elvis Presley's "Love Me Tender" from 1956 and "Just for You", "Peace in the Valley" and "
Jailhouse Rock" from 1957, and
Kinksize Session from 1964.
Twelve-inch EPs were similar, but generally had between three and five tracks and a length of over 12 minutes.
 Like seven-inch EPs, these were given titles.
 EP releases were also issued in
cassette and 10-inch vinyl formats.
 With the advent of the
compact disc (CD), more music was often included on "single" releases, with four or five tracks being common, and playing times of up to 25 minutes.
 These extended-length singles became known as
maxi singles and while commensurate in length to an EP were distinguished by being designed to feature a single song, with the remaining songs considered
B-sides, whereas an EP was designed not to feature a single song, instead resembling a mini album.
EPs of original material regained popularity in the
punk rock era, when they were commonly used for the release of new material, e.g.
Spiral Scratch EP.
 These featured four-track seven-inch singles played at 331⁄3 rpm, the most common understanding of the term EP.
Beginning in the 1980s, many so-called "singles" have been sold in formats with more than two tracks. Because of this, the definition of an EP is not determined only by the number of tracks or the playing time; an EP is typically seen
as four (or more) tracks of equal importance, as opposed to a four-track single with an obvious A-side and three B-sides.
In the United States, the
Recording Industry Association of America, the organization that declares releases "gold" or "platinum" based on numbers of sales, defines an EP as containing three to five songs or under 30 minutes.
 On the other hand,
The Recording Academy's rules for
Grammy Awards state that any release with five or more different songs and a running time of over 15 minutes is considered an album, with no mention of EPs.
In the United Kingdom, any record with more than four distinct tracks or with a playing time of more than 25 minutes is classified as an album for sales-chart purposes. If priced as a single, they will not qualify for the main album chart but can appear in the separate Budget Albums chart.
An intermediate format between EPs and full-length LPs is the
mini-LP, which was a common album format in the 1980s. These generally contained 20–30 minutes of music.
In underground dance music, vinyl EPs have been a longstanding medium for releasing new material, e.g.
Fourteenth Century Sky by
The Dust Brothers.