File with a .CONFIG extension contains different types of configuration data, usually in form of text, utilised by a variety of programs. It is a general file, it has no single fixed format, it depends on the program for which it has been written. Usually it can be read within a text editor, however, its manual editing is not advised in order not to disturb application’s functioning.

CONFIG files are used also during building and creating applications in different programming environments. Another example is the web.config file, which contains settings in the XML format, utilised by the ASP.NET applications created in the Microsoft Visual Web Developer environment in order to control web sites functioning.