A CONFIG file is a configuration file used by various applications. It contains plain text parameters that define settings or preferences for building or running a program. CONFIG files are often referenced by software development programs to configure applications.

An example CONFIG file is Microsoft's Web.config file, which can be edited with Visual Web Developer, a program included with Microsoft Visual Studio. This file contains XML configuration information that controls how a website works, from individual pages to an entire ASP.NET application. Since CONFIG files are stored in plain text, you can view and edit them with a text editor such as Microsoft Notepad. However, you should not edit a CONFIG file without first knowing its contents, since it may corrupt the file and cause its associated application to malfunction.