What is Spring Boot DevTools, and what does it do during development?

DevTools is a development-time-only dependency that speeds up the local feedback loop: it automatically restarts the application when it detects a classpath change (faster than a full manual restart, since it uses two classloaders and only reloads your own classes), enables LiveReload for the browser, and applies development-friendly default property overrides. It's automatically excluded from a production build/JAR, so it never adds overhead in a deployed environment.