Which dependencies to use between Firebase and Google Play Services?
<p>I recently started playing with Firebase, but I cannot completely understand its relation with Google Play Services. I know that Firebase is a mobile platform, and on Android it is based on Google Play Services, but why there are some modules with the same name of the ones of Google Play Services?</p>

<p>For example, in my <code>build.gradle</code> I can have:</p>

<pre><code>com.google.android.gms:play-services-auth:9.4.0
com.google.android.gms:play-services-ads:9.4.0
</code></pre>

<p>but also:</p>

<pre><code>com.google.firebase:firebase-auth:9.4.0
com.google.firebase:firebase-ads:9.4.0
</code></pre>

<p>I see that on <a href="https://firebase.google.com/docs/android/setup" rel="noreferrer">Firebase documentation</a> there is the list of available components (and note that the last one is actually a Google Play Services module):</p>

<pre><code>com.google.android.gms:play-services-appindexing:9.4.0
</code></pre>

<p>The <a href="https://developers.google.com/android/guides/setup" rel="noreferrer">same list for Google Play Services</a> is much longer, so some modules are not available using only Firebase dependencies. Which dependencies should I use and why? Can I use mixed dependencies?</p>