Configuration file that contains information about an update to a program installed with Advanced Installer; typically provided to clients via a software company's website; used to check if users have the latest version of the software installed and provides updates if necessary.

AIU files are saved in a plain text format and begin with the line: ;aiu; All AIU files contain the name of the program, the URL of the latest installer, the file size, and the path to the installation directory. They may also include a description of the installer, a list of features, bug fixes, the registry key, and the number of the current version.