A technology for layered software development using files is disclosed. In one method a runtime environment for a class of a layered software application is developed. A layer file folder is opened. The layer file folder is located in a computer file system and is for storing classes belonging to a layer of the layered software application. A class file is opened in the layer file folder. The class file comprises a text file representing the class of the layered software application that is being developed into a runtime environment. The class file further comprises data describing a method performed as part of the class. It is then determined if the method of the class file has been previously loaded into the runtime environment.