Files with the .WSF extension are executable files in the Windows operating system and contain source code for scripts written in the VBScript or JScript programming language, though they can also contain data written in the XML format. The system apps responsible for executing WSF files are WScript and CScript.

WSF files can also contain code written in other script languages, as long as those are installed in the system; with the help of XML tags, they also allow for the use of multiple languages in one file. Caution is advised while opening unknown WSF files, as they can be harmful to the system.