This project is aimed to developing an android Online Chatting System. Chat application is a feature or a program on the internet to communicate directly among Internet users who are online or who were equally using the internet. Chat application allows users to communicate even though from a great distance. Therefore, this chat application must be real-time and multi-platform to be used by many users. The programming language used to build server is Kotlin with Firebase online database system. This project has tried to incorporate all the advanced features of Kotlin such as to fulfill the aim of the project. The development of information and communication technologies are rapidly making one of the reasons for protecting information from the outsiders.