Educational software tools are considered to enrich teaching strategies, providing a more compelling means of exploration and feedback than traditional blackboard methods. Moreover, software simulators provide a more motivating link between theory and practice than pencil-paper methods, encouraging active and discovery learning in the students. The use and development of educational software is a field that has grasped the attention of teachers and researchers from different disciplines and theoretical frameworks in the last few years. In this paper, the authors present SoftwarE for Learning Formal languages and Automata theory (SELFA), an educational software simulator tool, designed to improve the quality of teaching in Theory of Computation courses. The aim of this tool is to make it easier to teach and to learn the main concepts of this subject, whose level of abstraction makes both activities difficult. The main advantage of this tool over other software tools designed with the same purpose, is that it has been developed using web technologies. This allows the user to collect and analyze data on how and when a student or group has used the tool. These numerical data can then be used to evaluate the student's work. (Contains 5 tables and 4 figures.)