title: Is `firebase-core` required for Firebase on Android?
body: <p>As far as I know, individual Firebase libraries like <code>firebase-auth</code> didn't used to require me to include <code>firebase-core</code>.</p>
  
  <p>However, I recently started a new Android project, and when I tried to build without <code>firebase-core</code>, I got the following Java compiler warning:</p>
  
  <p><code>Warning: The app gradle file must have a dependency on com.google.firebase:firebase-core for Firebase services to work as intended.
  </code></p>