What is the File Extension .Config?

by William M Rea

CONFIG is the extension for a configuration file. Configuration files are the initial settings for computer programs. They are used in the operating system, servers and some application programs.

Microsoft .NET

The CONFIG file type is primarily associated with the Microsoft ".NET" application suite, but it can also be associated with several others.

Microsoft DOS and Windows

In Microsoft files, DOS (disk operating system) primarily relies on config.sys for its initial settings. The Microsoft Windows family of operating systems and their attendant applications utilize a similar system of configuration files.


IBM’s OS2 uses a binary format for its configuration file and also has an .INI suffix.


Within CRISP (Computer Retrieval of Information on Scientific Projects), the CONFIG file is used to configure output from "Monte Carlo" computer trials and studies. CRISP is a searchable database of federally funded biomedical research projects.

Apple II

In Apple II, CONFIG files are used for initial settings for Mac computer programs.

RockBox MP3

Configuration files are also used in RockBox, an open source firmware for MP3 players.

About the Author

William Rea received an M.B.A. from the University of Tampa. His writing experience included being an office administrator for the U.S. Navy Reserve in Tampa, Fla., where he managed an office pool by making assignments, doing quality assurance on letters, and correcting officer fitness reports and enlisted evaluations. He has also published a number of articles for eHow.