Quarkus dev mode keeps an application running while you edit it. Save a code or configuration change, then refresh the browser or send another HTTP request: Quarkus recompiles and reloads the application in the background. This replaces the usual edit–build–restart loop with rapid feedback while developing in Java or Kotlin. section 1.1 section 3.1
Start dev mode from the project directory with `quarkus dev`. For a Maven project, use `./mvnw quarkus:dev`; for Gradle, use `./gradlew --console=plain quarkusDev`. The Quarkus CLI offers the same invocation for either build tool. Unlike running a packaged application, this workflow does not require a manual packaging step before trying a change. section 2.3
Change a REST greeting
Start dev mode, open `http://localhost:8080/hello`, and change the string returned by the REST resource’s `hello()` method. Save the file and refresh the page to see the new greeting. Console messages show that the application stopped and reloaded; pressing `s` in the running terminal can also trigger a reload without an HTTP request. The reload reuses the existing JVM rather than starting a new one. section 3.1.1 section 3.1
A compilation or library-usage error does not end the dev-mode process: HTTP requests receive error details instead of application content. Tests are a separate consideration. Continuous testing can run them automatically in the background, but it must be enabled; without it, the greeting exercise’s existing test runs during a full build and may fail until its expected response is updated. section 3.7 section 3.1.1
Dev mode also provides the running context for Dev UI, which exposes application insights, and Dev Services, which can manage development instances of resources such as databases. These are development aids, not a substitute for packaging and running the application with its production profile. section 3.7 section 2.3
