title: Are querystring parameters supported in OAuth 2.0 redirect URLs?
body: <p>I want to make sure I have correctly understood the (draft) spec, which states:</p>
  
  <blockquote>
    <p>The redirection endpoint URI MUST be an absolute URI as defined by<br>
    [RFC3986] section 4.3.  The endpoint URI MAY include an<br>
    "application/x-www-form-urlencoded" formatted<br>
    ([W3C.REC-html401-19991224]) query component ([RFC3986] section 3.4), 
    which MUST be retained when adding additional query parameters.  The<br>
    endpoint URI MUST NOT include a fragment component.</p>
  </blockquote>
  
  <p>Reason I ask is that neither Google or Facebook appear to preserve any querystrings.</p>