title: How to get to know from FB Login Web that a user has already logged in in native FB app and use it to login a user in web app?
body: <p>I don’t know if there is a term for this issue already. So will try to explain it.</p>
  
  <p>The question.
  How to get to know from FB Login web that a user has already logged in in native FB app and use that auth session to login a user in web app? So that a user doesn’t need to see FB login dialog and provide their credentials again.</p>
  
  <p>The problem.
  There are users who never use FB in mobile browsers on smart phones. Only FB native app.
  So when a user tries to login with FB in my web app, they are always asked to provide their credentials, email and password. And users complain that they are logged in already and don’t understand why they’re asked to login again. Many just do not remember their passwords.</p>
  
  <p>So, does FB Login API foresee this use case, a combination of logins? Is it possible to implement it?</p>
  
  <p>Similar question <a href="https://stackoverflow.com/questions/34351940/facebook-login-to-web-via-native-fb-app">Facebook login to web via native FB app</a></p>
  
  <p><strong>UPD1:</strong></p>
  
  <p>Found this <a href="https://developers.facebook.com/docs/facebook-login/overview/#use-cases" rel="nofollow noreferrer">here</a>. </p>
  
  <p>However the question still remains: <em>How to login in web app seamlessly without login dialog if logged in in FB native app</em>?</p>
  
  <blockquote>
    <p>Once someone has created an account on one platform, they can log into your app — often with a single click — on all your other platforms.</p>
  </blockquote>