Film serials were a type of film popular in the first half of the twentieth century. They were created early in film history as a hybrid format inspired by magazine serial literature which dated back to the mid-1800s. The first film serial, What Happened to Mary?, was released in the United States by Edison Studios in 1912. At this time most films were short subjects, usually only two film reels in length (approximately 20 minutes). This did not, however, provide much time to develop elements such as plot or characterisation. By the 1910s, some producers were experimenting with longer "feature" films, but this was very expensive and resisted by some studios. The serial format allowed a compromise between the two by combining individual short episodes (or chapters) into a longer narrative. The overall, single narrative is the distinction between a film serial and a film series. The individual episodes of the latter would have independent, stand-alone plots while containing the same characters.

It was the second American serial, The Adventures of Kathlyn, in 1913 that set the standard for the format. It was a collaboration between William Selig and the Chicago Tribune newspaper based on the success of What Happened to Mary?. Each of the thirteen chapters in the serial, bar the concluding chapter, ended in a cliffhanger, with some element of each chapter's plot incomplete, unresolved, even at a point of climax. The addition of cliffhangers to the format was extremely successful and they were used in almost every subsequent serial production. So integral were they to the format that serials themselves were often referred to "cliffhangers".

As feature films became standard, rather than an expensive experimental format, the film serial lost its original purpose. The format continued for some time, however, with the aim shifting towards the children's entertainment market. The coming of sound presented another significant problem for the film serial. Serials had become known for their action and stunt sequences but early sound recording equipment was expensive and bulky. Most studios could not afford this equipment and those that could did not believe it was possible to film action sequences with sound. In 1929, Mascot Pictures released the first serial with partial sound, called The King of the Kongo. Other serials followed suit for a time but it was Universal Pictures that released the first all sound serial, a western called The Indians Are Coming, in late 1930. Once it had been proven to be possible, most other studios began releasing sound serials of their own although some, such as Pathé, dropped out of the industry altogether.

The sound era of serials were dominated by three studios. Universal Pictures, which began serial production in 1914, continued regular production, the only major studio of the silent era to do so. Universal serials took advantage of the company's other assets and featured stronger writing and technical quality than those produced by rival studios. Mascot Pictures continued for a few years until 1935 when it was merged with other companies to become the serial unit of Republic Pictures. Republic serials were known for their action, stunts and special effects. Columbia Pictures was the last of the three to begin serial production, with 1937's Jungle Menace. Their serials were often cheaply made, even compared to the low budgets of other serial productions, but were still popular.

The end of the serial format came with the end of World War Two. Production costs increased with material becoming more expensive and unionisation, which had previously been stopped by the Great Depression, became widespread. Serial budgets had never been large and could not cope well with the changes. Many cost saving measures were introduced or exploited more fully than had been the case in the past. For example, later serials contain large amounts of stock footage, with entire scenes taken from earlier productions and edited into the newer releases. At about the same time the typical serial audience was being stolen by the arrival of television. The threat from the new medium was compounded by television showings of the older, better produced, serials in competition with the newer releases in theaters.

Universal was the first to end its serial production with The Mysterious Mr. M in 1946. This left only two serial producers, who continued regular but diminishing production into the next decade. Republic was the next to stop, ending with King of the Carnival in 1955. Columbia spent one year as the only company still producing serials until Blazing the Overland Trail in 1956.

Examples

Episode 1 of the Perils of Pauline

The most famous serial of the silent era, and still iconic to this day, is The Perils of Pauline. It was released by Pathé in 1915 with actress Pearl White playing the title character. It was the French studio's first American success, began the golden age of the silent serial and launched Pearl White's career as the "Queen of Serials". Not all of this serial survives but prints of many episodes are available commercially.

Flash Gordon, released by Universal in 1936, is the most famous example of the sound serial era. Buster Crabbe played Flash Gordon and Charles Middleton was cast as Ming the Merciless. This serial was Universal's attempt to regain an adult audience for the format and benefitted from a larger budget in addition to the studio’s access to props and material from their own feature films. It did not gain the adult audience but it was a commercial success. Much like The Perils of Pauline, it made Buster Crabbe the "King of Serials" and began the golden age of the sound serial. It was followed by two sequels, Flash Gordon's Trip to Mars (1938) and Flash Gordon Conquers the Universe (1940), as well as the semi-sequel Buck Rogers (1939) which also starred Buster Crabbe in the title role.

Columbia, which managed to acquire more licensed properties than the other studios, had one of its most influential releases in 1943's Batman. The production was cheap, with unintentional humour and poor direction but it remained popular. It was followed by one sequel, Batman and Robin (1949), but it's major successor came decades later on television. Theater showings on the serial, with all fifteen chapters in one sitting under the title "An Evening with Batman and Robin", became very popular for their "camp" value in the 1960s. This led the commissioning in 1966 of the Batman television series starring Adam West and Burt Ward. The serial is also responsible for the now standard appearance of the character Alfred in all media and the style of the television show affected the original comics for several years.

Republic had many successes, with the entire sixteen serial run directed by William Witney and John English, between The Lone Ranger (1938) and Dick Tracy vs. Crime Inc. (1941), considered as the best. Highlights include Drums of Fu Manchu (1940), which featured strong use of cinematography to add to the suspense, Mysterious Doctor Satan (1940), originally intended as a Superman adaptation, and especially Adventures of Captain Marvel (1941), which was the first film adaptation of a superhero comic. Spy Smasher in 1942, directed by William Witney alone, is also often cited as Republic's best.