title: Do I need Firebase to use Google Sign In in my Android app?
body: <p>I have implemented everything I needed to implement to use Google Sign In (at least I think I have).</p>
  
  <p>I have my Google Sign In button, I can click it, it prompts me to select an account but I always get error 12500 (Login Failed).</p>
  
  <p>I've been looking around for a solution to this issue and have heard a lot about SHA-1 and Firebase. Not sure what Firebase is, nor is it mentioned in any of the following documentation:</p>
  
  <p><a href="https://developers.google.com/identity/sign-in/android/sign-in" rel="nofollow noreferrer">https://developers.google.com/identity/sign-in/android/sign-in</a></p>
  
  <p><a href="https://developers.google.com/identity/sign-in/android/start-integrating" rel="nofollow noreferrer">https://developers.google.com/identity/sign-in/android/start-integrating</a></p>
  
  <p>Do I absolutely need Firebase to get Google Sign In to work? If so, what do I have to do? If not, what else could be causing my 12500 error?</p>