title: Is there a way to allow login with a single Facebook app on multiple subdomains?
body: <p>I'm trying to build a "RSVP to this event" action using the Facebook JS SDK.</p>
  
  <p>All of our sites run on multiple subdomains (<code>event1.example.com</code>, <code>event2.example.com</code>) and I'm trying to setup a single Facebook app that will allow people to RSVP.</p>
  
  <p>Ideally I'd like to be able to specify wildcard subdomains in the <code>Valid OAuth redirect URIs</code> settings, but Facebook doesn't seem to allow that.</p>
  
  <p>Previous StackOverflow answers said that either just putting in the top-level domain or leaving that field blank would work (<a href="https://stackoverflow.com/questions/7666161/facebook-app-redirecting-to-different-subdomains">for example</a>), but I always get the <code>This redirect failed because the redirect URI is not whitelisted in the app’s Client OAuth Settings</code> error.</p>
  
  <p>Frustratingly, we shouldn't need any sort of redirect callback to the server.  I just want a short-lived token to post the event RSVP which should be possible client-side only.</p>
  
  <p>Is there any way to accomplish this?  </p>
  
  <p>The options I can think of...</p>
  
  <p><strong>One app per subdomain</strong> We have 100s of subdomains, so creating Facebook apps for each isn't going to work (plus that's a manual process)</p>
  
  <p><strong>List all subdomains as redirect URIs</strong> it appears <a href="https://stackoverflow.com/questions/42999831/facebook-login-from-subdomains-too-many-valid-oauth-redirect-uris">Facebook has a limit</a> on the number of redirect URIs, plus this is also a manual process - there's no API endpoint for adding these</p>
  
  <p><strong>Set the redirect URI via JS to our root domain</strong> and then just ignore the callback - this seemed promising, but calling <code>FB.login</code> with a <code>redirect_uri</code> param gave an error: <code>When using FB.ui, you should not specify a redirect_uri.</code> Is there a way to do this without <code>FB.login</code>?</p>
  
  <p><strong>Somehow let Facebook know we don't care about those redirects at all</strong> -- is there some other way to request permissions and make a JS API call without needing the oauth redirect?</p>
  
  <p>Thanks in advance for any insights...</p>