The Functional Mock-up Interface (FMI) is an open standard for the tool-independent exchange and integration of simulation models that are provided by various tool vendors in the form of Functional Mock-up Unit container files (FMUs). In many cases, when using an FMU in a simulator tool, the modeling tool that generated the FMU is no longer needed. FMI thus simplifies the use of best-in-class tools for physical domain-specific modeling tasks and the consistent reuse of models in different development phases and in different company departments.

The FMI standard defines FMUs providing their model implementation as C source code, in binary form, or both. Binary FMUs enable IP protection scenarios, e.g., when model exchange between different companies is required.