title: Android - How to detect same user from multiple devices?
body: <p>I am developing an app that sends user-created data to a server.</p>
  
  <p>Is it possible to recognise the same user when he is using the app on different devices <strong>without</strong> my app having to request access to his Google account, requiring additional permissions or asking him to create custom login credentials? (This is important as my app needs to work for 'anonymous' users.)</p>
  
  <p>My app uses push notifications and, for any given user, I understand that the token ID generated by FireBase may be the same for each of his device installations of the app. So I am considering using these token IDs to identify the same user across multiple devices. However, I'm not sure how reliable that approach would be - or if there is a better way?</p>
  
  <p>NB - I found <a href="https://developer.android.com/training/articles/user-data-ids.html#e_handle_multiple_installations" rel="nofollow">Best Practices for Unique Identifiers</a> (the <a href="https://developer.android.com/training/articles/user-data-ids.html" rel="nofollow">Handling Multiple Installations</a> section in particular), but it hasn't helped.</p>