title: Where does the HTTP Request Header X-Requested-With come from
body: <p>As we know we can use the <code>X-Requested-With</code> http request header to judge that if a http request comes from Ajax or not.</p>
  
  <p>Many javascript framework will auto add <code>X-Requested-With</code> header in their ajax request，such as <a href="http://api.prototypejs.org/ajax/">jQuery Ajax</a>，<a href="https://github.com/sstephenson/prototype/blob/master/src/prototype/ajax/request.js">Prototype Ajax</a>.And as the wiki of <a href="http://en.wikipedia.org/wiki/List_of_HTTP_header_fields">List of HTTP header fields</a> says the <code>X-Requested-With</code> is a <strong>non-standard request header</strong>.</p>
  
  <p>After google many times , I haven't found who first come up with the <code>X-Requested-With</code> request header.</p>
  
  <p>So I want to know if anybody else know where the <code>X-Requested-With</code> comes from ? Thanks...</p>