title: What is the difference between ActionController::API and ApplicationController
body: <p>I have some controllers that are used for API responses, but the rest of the app is a regular Rails 5 application.</p>
  
  <p>What is the difference if I change my base class to</p>
  
  <pre><code>ApplicationController::API
  </code></pre>
  
  <p>versus</p>
  
  <pre><code>ApplicationController
  </code></pre>
  
  <p>I noticed if I do ::API then I <strong>need</strong> to add the json: when rendering, before I could just render <code>msg</code></p>
  
  <p>Behind the scenes is the request/response much leaner when inheriting from API?</p>
  
  <pre><code>class Api::V1::TestController &lt; ????
    def index
      msg = {status: "ok", message: "hello world"}
      render json: msg
    end
  end
  </code></pre>