File with an .EP extension contains a project of a graphic user’s interface, comprised of different types of elements, depending on requirements of given program and platform. This may include different shapes, web elements, desktop widgets or data flow diagrams. EP files are created with the open-source Pencil tool. They do not include any functionality, they only show how a program is supposed to look like.

The Pencil software is used to create the so-called software’s layouts for computer programs, web sites or mobile applications. It enables to export a project into popular graphic formats and documents, for instance – PNG, PDF, ODT or WEB pages, due to which they can be opened by the target clients easily or attached to documentation.