An Index stores information describing the contents of the BDMV directory.

The Index Table is a top-level table that defines a BD-ROM disc's Titles and Top Menu. This function depicts the Titles of various media - movies, video programs, music albums, and games. It also determines their entry points, including First Playback and Top Menu, which are linked to the connected Movie or BD-J object. The Player refers to this table whenever a Title or Menu is executed. 

For example, whenever the Title Search or Menu operation is called, the Player refers to this table to determine the corresponding Movie Object/BD-J Object that is to be executed. 

When the disc is inserted, it will automatically play the "First Playback" defined in the Index table, either a Movie Object or a BD-J object. The Index table is located in the index.bdmv file and is written in binary machine code for the player to read. There's only one Index Table file and only 999 Titles are allowed.

There are three types of titles: 

• Movie title - A title for a movie. Example: Multiple movies, different cuts, etc.
  

• Interactive title - Usually for HDMV menus or interactive pages.
  

• BD-J title - A title for BD-J applications such as menus, games, or an interactive mode.

There's only one Index Table file and only 999 Titles are allowed.

 If you open an Index file in a hex editor, you can see several magic numbers. The file's main magic number is INDX0100 and INDX0200. For Ultra HD Blu-ray, the file's main magic number is INDX0300.

• @ = Movie Title 
• p = Interactive Title
• L = BDJ title

 Sometimes the disc author or content provider will present its name in the file.