title: How does Firebase Authentication detect if a physical device is being used?
body: <p>When Firebase Authentication is run in an emulator, the following error is triggered:</p>
  
  <pre><code>This app is not authorized to use Firebase Authentication. Please verify that the correct package name and SHA-1 are configured in the Firebase Console.
  </code></pre>
  
  <p>How does Firebase detect if an emulator is being used?</p>
  
  <p>EDIT: I'm meant to refer specifically to phone auth.</p>