JACOsub is a program (now open source) designed for displaying timed sequences of titles and graphics over a video. Professional-quality output and flexibility have been the primary goals since the program's inception. It was originally written for the Japanese Animation Club of Orlando (JACO) to lay English subtitles over Japanese-language films and television shows. The program has spread and grown in popularity due to its extremely flexible script format, clean multi-buffered title transitions, and other features described in the next section.
The development of JACOsub has been primarily user-driven. Most of the program's more interesting features exist because users suggested them. Because of the valuable input given by so many people, JACOsub has become an exceptionally powerful program while retaining its initial simplicity at the same time.