.ARX File Extension
File TypeAutoCAD Runtime Extension File
What is an ARX file?
Extension file created for AutoCAD, a design and engineering application for 2D and 3D products; contains an application component written using Autodesk's ObjectARX, an object-oriented API that allows developers to customize and extend AutoCAD using C++, C#, and VB.NET program code.
ObjectARX SDKs are released with each version of AutoCAD, so you need to match the SDK version with the appropriate AutoCAD version.