Since the 1980s, the term "short subject" has come to be used interchangeably with "short film," an international, academic term used to mean a contemporary non-commercial motion picture that is substantially shorter than the average commercial feature film. There is no clear definition of the maximum length of a short film, the Academy of Motion Picture Arts and Sciences classify it as 40 minutes, while the Internet Movie Database refer to any film lasting less than 45 minutes as a short subject. The short-film form is to the full-length film what the short story is to a full-fledged novel.

Short films often focus on difficult topics which longer, more commercial films usually avoid. Filmmakers benefit from larger freedoms and can take higher risks, but they must rely on festival and art house exhibition to achieve public display. Most short films are better known outside the United States than within, due to less rigidity of audience expectation as to program content, arrangement and length outside the U.S. However, film shorts are often a popular extra feature on a film's DVD. For instance, Pixar's DVD releases of its feature films typically includes not only a short that was distributed with the feature film in its initial theatrical release but also an original creation featuring the characters from the feature itself. Likewise, Warner Brothers often includes selected animated shorts from its considerable archives on DVD releases of its family-oriented films that have a thematic relationship.

Films such as S. Luciani's Dolls show how professional actors and crews still choose to create short films as alternative form of expression. Short films are often popular as first steps into the cinematic art among young filmmakers. They are cheaper and easier to make, usually don't take very long to produce, and their brevity makes shorts more likely to be watched by financial backers and others who want some demonstration of a filmmaker's ability (or, conversely, the format allows for more experimentation since most of them are unlikely to be seen by a wide audience).

Short filmmaking is also growing in popularity among amateurs and enthusiasts, who are taking advantage of affordable equipment. "Prosumer" or semi-professional cameras now cost under USD$3,000, and free or low-cost software is widely available that is capable of video editing, post-production work and DVD authoring.