title: Firebase Cloud Messaging - Are GCM canonical IDs still necessary?
body: <p>I've been reading on canonical IDs in GCM and how they help to rectify sending duplicate push notifications and with security.  But now with Firebase Cloud Messaging (FCM), does this issue still exist?</p>
  
  <p>I am the registration part has been taken away from the developer now and we just wait for a token refresh as per below:</p>
  
  <pre><code>    public class MyFirebaseInstanceIDService extends FirebaseInstanceIdService {
  
      @Override
      public void onTokenRefresh() {
          // Get updated registration ID
          String refreshedToken = FirebaseInstanceId.getInstance().getToken();
          Logger.d("Refreshed FCM token: " + refreshedToken);
      }
  }
  </code></pre>
  
  <p>Some info on canonical IDs can be found <a href="https://stackoverflow.com/questions/27072824/how-to-get-canonical-id-from-gcm">here</a>.</p>