why do I need @ResponseBody

Hi Thomas! @ResponseBody means that the controller's return value should be used as the body of the response. That is, the HTTP response should be whatever is stated in the return value. Without the annotation, Spring would try to use the configured template engine (Thymeleaf, unless you configured otherwise) to render a template named "List of all the Gifs". This is why using a browser to visit the URI listed in your @RequestMapping annotation yields a plain page with the text "List of all the Gifs". There is no template rendering happening here, like you'll see (or have now seen) later in the course. I show you this annotation in advance of talking about template rendering, so if you have yet to move on, you'll see that we end up removing the annotation.