The SSA format was first introduced in the early 2000s by a software developer named Ian Beale. At the time, it was designed to be a more feature-rich alternative to the SubRip (.srt) subtitle format. Over the years, SSA has become a widely-used format for storing subtitles and closed captions for video files.
It is famous for enabling karaoke effects , where text highlights in sync with music, and complex animations often seen in anime fansubs. SSA vs. ASS: The Evolution .ssa video format