Spring Boot Configuration Priority Order If you have ever stared at your Spring Boot application wondering "Why is it picking the wrong port?" or "Where is this database URL coming from?" You are not alone. One of the most common sources of confusion among Java developers is how Spring Boot decides which configuration value to use when the same property is defined in multiple places. This guide breaks down the externalized configuration property priority into a simple, visual hierarchy that you can bookmark for your next project or technical interview. What Is Externalized Configuration in Spring Boot? As per Spring Boot official documentation on externalized configuration, Externalized configuration means keeping your application settings outside your compiled code so you can change behavior without rebuilding the JAR. Spring Boot supports multiple