Files with .SO extension contain libraries used by various processes. SO files can only by accessed using source code compiler. SO files typically contains libraries written in C or C++ programming language.

SO format is part of the ELF (Executable and Linkable Format) technology. ELF files are used in Unix-based systems and game consoles such as PlayStation or Sega Dreamcast. SO libraries store various tools for reading data structure and interpreting CPU instructions.