VobSub (SUB) is an image-based subtitle format used primarily for DVDs. The SUB file contains the subtitle images stored in MPEG-2 streams. It works alongside the corresponding IDX file, which holds the timing and coloring information.

The VobSub Subtitles file, developed in the late 1990s, is the main component of the VobSub subtitle format used for DVDs. VobSub enabled precise subtitle rendering, supporting various languages and fonts, and could include multiple subtitle tracks within a single DVD, making DVD video adaptable for international markets for the first time. Despite the shift to digital formats, the VobSub SUB file remains relevant for DVD ripping and archival purposes.