An AS file is a source code file written in AngelScript, a scripting library used to extend the functionality of applications via external scripts. It contains AngelScript, which includes functions, variables, script classes, expressions, statements, and object handles.

AngelScript class syntax is similar to C/C++. AngelScript can be used with any C++ IDE and C/C++ functions can be called within an AngelScript environment. AngelScript is primarily used in the development of video games such as Rigs of Rods, Penumbra: Overture, Dustforce, and Amnesia: The Dark Descent. AS files can be edited with basic text editors. NOTE: AS files are also used to store ActionScript source code.

File created in the AppleSingle format, an archiving format used by older Macintosh systems that have the A/UX operating system; saves both the resource fork and the data fork in a single file; now considered an obsolete file format.