The WXI extension is given to files associated with the Windows Installer XML (WiX) installer development software package. Technically, WXI is a plain text file that performs a similar role to the header files in the C ++ programming language. Its main part is the <Include> section. Based on WXI files, developers create installation packages in the form of MSI or MSM files.

Creating installation packages with WiX is done using the command line. WiX is a tool distributed under the Microsoft Reciprocal License.