INI files are plain text configuration files commonly used to store settings and preferences for software applications. The name "INI" originates from the term "initialization." Their structure is simple, organized into sections (enclosed in brackets [ ]) containing related key-value pairs (key=value). This differs from more complex formats like JSON or XML by being human-readable and editable with any basic text editor, requiring minimal processing overhead. They are primarily used for static, user-modifiable configuration.

For example, the Windows operating system historically relied heavily on INI files (like win.ini or system.ini) for system-wide settings such as desktop appearance and hardware drivers. Many applications, particularly older desktop software, also use INI files for user preferences; media players like Winamp stored settings like playback options and plugin paths in winamp.ini. They are less common but still used in specific modern tools or alongside other config formats due to their simplicity.

The main advantage of INI files is their extreme simplicity and human readability, making them easy to understand, create, and modify without specialized tools. However, they lack standardization, offering no native support for complex data types, nesting, or formal data validation. While largely superseded by XML, JSON, YAML, or platform-specific alternatives like the Windows Registry for complex needs, INI files remain relevant for straightforward, editable configuration due to their enduring simplicity and portability across systems.