In addition to the available functionality in COMSOL Multiphysics and the add-on products included in your license, you can add custom functionality by defining methods and settings forms and by combining them into add-ins for general use in any model. There are also built-in tools for comparing the contents of two models. All this functionality is available from the Developer toolbar (see Developer Toolbar). There are also a Java Shell window for interactively using the COMSOL Java® API and an Add-in Libraries window for adding existing add-ins to a model. See the following sections for more information: