Provided is a method of providing a user-customized user experience (UX)/user interface (UI) during a runtime of a web application by using a room template, the method including: transmitting, from a user device to a service server, a room entrance-related access request; requesting, by the service server, an application programming interface (API) server to generate an access token including room template information; transmitting the access token generated by the API server to the user device via the service server; transmitting, by the user device, the access token to the API server; and providing, by the API server, a UX/UI to the user device based on the room template information.