title: What is minimum version of Google Play Services to use Firebase?
body: <h1>Background</h1>
  
  <p>I'm developing an app using <code>Firebase</code> features (<code>Realtime Database</code>, <code>Firebase Messaging,</code> <code>Analytics</code>, <code>Crash Reporting</code> and <code>Auth</code> [<code>Facebook</code>]). In my country, most of the users don't have wifi and rarely upgrade apps (including <code>Google Play Services</code>).</p>
  
  <h1>Question</h1>
  
  <ol>
  <li><p>As the title suggests, I would like to know the minimum version (the lowest). I'm also willing to remove some features if it will help to lower the Google Play Services version.</p></li>
  <li><p>Do I need to check google play service version in my application code or will Firebase check for me?</p></li>
  </ol>
  
  <h1>Finding so far and I'm confused,</h1>
  
  <ul>
  <li><a href="https://groups.google.com/d/topic/firebase-talk/M8Rop0IMsSw/discussion" rel="noreferrer">This post</a> say min version is 9.0</li>
  <li><a href="https://groups.google.com/forum/?#!msg/firebase-talk/VB_MqWdP30k/QJk_vd2EAgAJ" rel="noreferrer">This post</a> say min version is 8.1.15 </li>
  <li><a href="https://stackoverflow.com/questions/38627880/firebase-for-play-services-below-9">This SO question</a> say developer no need to check <code>Google Play Services</code></li>
  <li>but, <a href="https://firebase.google.com/docs/cloud-messaging/android/client#sample-play" rel="noreferrer">This doc</a> say developer need to check <code>Google Play Services</code></li>
  </ul>