There is an increasing trend around the world that one organization owns and operates several websites. However, it often leads to problem that a user needs to remember multiple login accounts and passwords to log into different sites within the same organization due to database existing independently from each other. Thus, one single sign-on to websites within the same organization is commonly requested. Within the scope of the article, the authors propose solutions and building system of single sign-on services based that provide services of user authentication based on concentrated user database. The system is built based on the exploitation of the independence of the foundation of web services, the ability to share cookies between browsers and web applications. The paper also conducts application testing for the sign-on system that has already been built.