A DIZ file is a plain text file that describes the program or files within a .ZIP archive in which it is also included. It is a small file since it only contains a brief description that typically consists of 10 lines of text or less with each line being less than 45 characters. DIZ files can be opened using a text editor, such as Microsoft Notepad or Apple TextEdit.
DIZ files were originally used for distributing files via BBS (bulletin board systems) with the FILE_ID.DIZ filename. The FILE_ID stands for "file identification" and DIZ stands for "Description in Zip file." The information contained in FILE_ID.DIZ files provided system administrators with helpful descriptions of each file that was uploaded to the system.
As the popularity of bulletin board systems declined over the years, FILE_ID.DIZ files became less common. However, DIZ files are still used by the Warez scene, which is a community of people that illegally distribute copyrighted content. These users typically include FILE_ID.DIZ files with their ZIP distributions of unlicensed software.