title: Why does firebase hosting return a complete html response for a request on a non existing resources?
body: <p>My question is about the unexpected response from the firebase hosting server for non existing resources.</p>
  
  <p>In my case the static index.html references a css file with <code>&lt;link rel="stylesheet" href="main.css"&gt;</code>. This file does not exist on the firebase hosting server. Therfore I would have expected the server to respond with the status code 404. But the server returns a complete html document instead:</p>
  
  <pre><code>&lt;!DOCTYPE html&gt;
  &lt;html&gt;
  &lt;head&gt;
  &lt;meta charset="utf-8"&gt;
  &lt;meta name="viewport" content="width=device-width, initial-scale=1"&gt;
  &lt;title&gt;Welcome to Firebase Hosting&lt;/title&gt;
  
  &lt;!-- update the version number as needed --&gt;
  &lt;script defer src="/__/firebase/4.12.1/firebase-app.js"&gt;&lt;/script&gt;
  &lt;!-- include only the Firebase features as you need --&gt;
  &lt;script defer src="/__/firebase/4.12.1/firebase-auth.js"&gt;&lt;/script&gt;
  &lt;script defer src="/__/firebase/4.12.1/firebase-database.js"&gt;&lt;/script&gt;
  &lt;script defer src="/__/firebase/4.12.1/firebase-messaging.js"&gt;&lt;/script&gt;
  &lt;script defer src="/__/firebase/4.12.1/firebase-storage.js"&gt;&lt;/script&gt;
  &lt;!-- initialize the SDK after all desired features are loaded --&gt;
  &lt;script defer src="/__/firebase/init.js"&gt;&lt;/script&gt;
  
  &lt;style media="screen"&gt;
    body { background: #ECEFF1; color: rgba(0,0,0,0.87); font-family: Roboto, Helvetica, Arial, sans-serif; margin: 0; padding: 0; }
    #message { background: white; max-width: 360px; margin: 100px auto 16px; padding: 32px 24px; border-radius: 3px; }
    #message h2 { color: #ffa100; font-weight: bold; font-size: 16px; margin: 0 0 8px; }
    #message h1 { font-size: 22px; font-weight: 300; color: rgba(0,0,0,0.6); margin: 0 0 16px;}
    #message p { line-height: 140%; margin: 16px 0 24px; font-size: 14px; }
    #message a { display: block; text-align: center; background: #039be5; text-transform: uppercase; text-decoration: none; color: white; padding: 16px; border-radius: 4px; }
    #message, #message a { box-shadow: 0 1px 3px rgba(0,0,0,0.12), 0 1px 2px rgba(0,0,0,0.24); }
    #load { color: rgba(0,0,0,0.4); text-align: center; font-size: 13px; }
    @media (max-width: 600px) {
      body, #message { margin-top: 0; background: white; box-shadow: none; }
      body { border-top: 16px solid #ffa100; }
    }
  &lt;/style&gt;
  &lt;/head&gt;
  &lt;body&gt;
  &lt;div id="message"&gt;
    &lt;h2&gt;Welcome&lt;/h2&gt;
    &lt;h1&gt;Firebase Hosting Setup Complete&lt;/h1&gt;
    &lt;p&gt;You're seeing this because you've successfully setup Firebase Hosting. Now it's time to go build something extraordinary!&lt;/p&gt;
    &lt;a target="_blank" href="https://firebase.google.com/docs/hosting/"&gt;Open Hosting Documentation&lt;/a&gt;
  &lt;/div&gt;
  &lt;p id="load"&gt;Firebase SDK Loading&amp;hellip;&lt;/p&gt;
  
  &lt;script&gt;
    document.addEventListener('DOMContentLoaded', function() {
      // // 
      // // The Firebase SDK is initialized and available here!
      //
      // firebase.auth().onAuthStateChanged(user =&gt; { });
      // firebase.database().ref('/path/to/ref').on('value', snapshot =&gt; { });
      // firebase.messaging().requestPermission().then(() =&gt; { });
      // firebase.storage().ref('/path/to/ref').getDownloadURL().then(() =&gt; { });
      //
      // // 
  
      try {
        let app = firebase.app();
        let features = ['auth', 'database', 'messaging', 'storage'].filter(feature =&gt; typeof app[feature] === 'function');
        document.getElementById('load').innerHTML = `Firebase SDK loaded with ${features.join(', ')}`;
      } catch (e) {
        console.error(e);
        document.getElementById('load').innerHTML = 'Error loading the Firebase SDK, check the console.';
      }
    });
  &lt;/script&gt;
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>Is it possible to configure firebase hosting to return the status code 404 instead of html?</p>