Configuration file

In computing, configuration files, or config files configure the parameters and initial settings for some computer programs. They are used for user applications, server processes and operating system settings. The files are often written with ASCII encoding (rarely UTF-8) and line-oriented, with lines terminated by a newline or carriage return/line feed pair (CR LF), depending on the operating system. In operating systems that categorise files by extensions, software-dependent extensions .cnf, .conf, and .cfg are often used.

Some applications provide tools to create, modify, and verify the syntax of their configuration files; these sometimes have graphical interfaces. For other programs, system administrators may be expected to create and modify files by hand using a text editor. For server processes and operating-system settings, there is often no standard tool, but operating systems may provide their own graphical interfaces such as YaST or debconf.

Some computer programs only read their configuration files at startup. Others periodically check the configuration files for changes. Users can instruct some programs to re-read the configuration files and apply the changes to the current process, or indeed to read arbitrary files as a configuration file. There are no definitive standards or strong conventions.