A software platform developed by Microsoft. There are many programming languages that all "boil down" to .NET, for instance, C#, VB.NET, etc.

In order to run a program written in a .NET language, you must have the ".NET Framework" installed on your computer.

.NET is required for the old DCOM device connections (OPC-DA), and FactorySQL is written in various .NET languages, and runs on the .NET framework. This requirement is phasing out as more and more devices are available through OPC-UA drivers.