YML is a document file that stores data in YAML format. YML files perform similar function to XML files which store various type of data in human-readable and language-independent format. YML format was developed in 2001.

YML file is not a stand-alone computer program, bu a support file that can be utilized by many programming languages to extend their functions. YML format offers simple data structure which can be edited using any text editor. YML standard is actively developed and many new features are added regularly.