Mobile application development with React Native, the main motivation for this thesis is to check and research the process, features and challenges of using the React Native framework in mobile application development. The knowledge gathered through the thesis will be valuable in the future when assessing whether a cross-platform development project should be completed using the React Native framework. Also to check whether there are any obvious difficulties that would discourage future use. This thesis goes over a simple application developed with React Native to help reduce the workload of tracking job application, instead the application will automatically fetch and filter those applications from user's email. This thesis uses many different external API(Application Programming Interfaces) for the most effective way of filtering email. React Native was chosen for this project because of its growing popularity among cross platform application development. The knowledge gained through this thesis is very insightful in modern mobile application development.