Project components

OpenFisca is a modular project. Depending on your goals, you will install and interact with one or several of the OpenFisca Components.

OpenFisca schema


The Web API lets you access the legislation Parameters and Variables.

Example: Mes Aides uses the OpenFisca Web API to calculate OpenFisca-France benefits.

Extensions Packages

Extensions add on the capacities of a country-package.

Example: See Paris extension and Rennes extension on top of OpenFisca France.

Country package

Country Packages are the basic modules of OpenFisca. They define the Parameters, Entities and Variables of a country.

  • To install an existing Country Package, head to that package’s documentation.

OpenFisca Core

OpenFisca-Core is the main engine: it is the common interface to every Country Package. It binds the Country Package(s), Extension(s) and the engine together. OpenFisca-Core is also where the API is packaged.