title: Elixir/Phoenix - Accessing user's cookie: conn.cookies vs conn.req_cookies vs conn.req_headers
body: <p>So i'm trying to implement something like Imgur, where an user who isn't a member on the website can upload, and continue to edit that upload (until the cookie is reset). </p>
  
  <p>When looking at the <code>conn</code> struct, there are 3 places where the user's cookie appears. </p>
  
  <pre><code>conn.cookies["_APPNAME_key"]
  conn.req_cookies["_APPNAME_key"]
  List.keyfind(conn.req_headers, "cookie", 0)
  </code></pre>
  
  <p>These all return the same cookie (except the last one has "_APPNAME_key=COOKIE" vs "COOKIE" for the other 3)</p>
  
  <p>What is the difference between the three? Is there one I should use instead of the others?</p>