In continuation to series of articles on Spring Security, here in this article we will learn 'How to implement Security in Spring Boot using UserDetailsService With Spring Boot 3?'. After going through the previous articles, I hope we all are very familiar with basics of Security and even the basics of Security in a Spring Boot application. After the release of Spring Boot 3, here we are going to implement 'Spring Security UserDetailsService Using Spring Boot 3'. In this article, we will create a user registration form and save users with their roles in the database. Then, based on the user role, we will check the authentication and authorization functionalities with the help of predefined UserDetailsService. To illustrate, we will take some