In the early stages of web application development, web developers built the solution without considering the documentation and modelling of the application. Today companies experience problems when working with the management of web applications, due to that they grow in size and new requirements are added. In response to this web developers become more and more aware of the importance of using a modelling language to design and document the system [CFB00]. This thesis will compare two modelling languages, WebML and UML. The thesis importance lies on WebML, the reason for this is that it is a modelling language developed specifically for web application development. The purpose with the thesis is to make web developers aware of the relatively new modelling language WebML for designing web applications. The thesis aims to describe WebML in comparison to UML and to show differences between the languages. By doing this it will be possible to see whether a company benefits by adapting to WebML or not. By having conducted questionnaires and a case study we have realised that WebML is a small language in comparison to UML and therefore easier to implement. WebML could be used as a complement to UML when it already is used in a company, due to that it give the developers a better overview of the structure and design of the application.