Why is localhost:8080 used?

Port 8080 is the standard alternative to HTTP port 80. It is the default for Apache Tomcat, Spring Boot, Jenkins, and many proxy servers.

How to change Spring Boot default port from 8080?

Open your 'application.properties' file and add the line: 'server.port=9090' (or any other free port).

Localhost 8080: Spring Boot, Vue & Tomcat Troubleshooting Guide

Why isn't Localhost 8080 working?

If you see "Whitelabel Error Page" or "Connection Refused", use this guide tailored for backend and proxy services.

1. Spring Boot / Tomcat Startup

Unlike Node.js, Java servers take a moment to start. If you just ran the command, wait 10-15 seconds.

Check your console for the Spring logo. If it failed, check for stack traces.

                    mvn spring-boot:run
                    
// or for Gradle

                    ./gradlew bootRun

2. Port 8080 is Busy (Oracle / Jenkins)

Port 8080 is the most "crowded" port. Software like Oracle Database XE, Jenkins, or older Skype versions often claim it silently.

Check what is using port 8080:

# Mac / Linux
lsof -i :8080

# Windows (PowerShell/CMD)
netstat -ano | findstr :8080

3. How to Change the Port

If you can't kill the conflicting process, simply change your project's port.

Spring Boot (application.properties):

server.port=9090

Vue.js (vue.config.js):

                    module.exports = {
                      devServer: {
                        port: 8081
                      }
                    }
                

4. Docker Container Mapping

If you are running a Docker container, ensure you mapped the ports correctly in your run command.

docker run -p 8080:80 my-web-app

The first 8080 is your localhost port. The second 80 is the container's internal port.