title: trouble changing request headers in Firefox with AngularJS
body: <p>My backend requires the 'Content-Type' request header to be exactly 'application/json'. This is a CORS request and everything works fine in Chrome. The exact header, from developer tools network tab source:</p>
  
  <pre><code>Content-Type: application/json
  </code></pre>
  
  <p>I set this in AngularJS with $http.default.headers.post and it works fine in Chrome. However it doesn't work in Firefox. Firefox sends this instead:</p>
  
  <pre><code>Content-Type: application/json; charset=UTF-8
  </code></pre>
  
  <p>I tried to change headers by:</p>
  
  <ul>
  <li>settings $http.default.headers (for .post, .common)</li>
  <li>setting custom headers for one request</li>
  <li>using an $http interceptor</li>
  </ul>
  
  <p>All of those methods work well in Chrome, but not in Firefox. <strong>The request contains data</strong>.</p>
  
  <p>If I remove the 'Content-Type' header all together, it still is sent, but then it is:</p>
  
  <pre><code>Content-Type: text/plain; charset=UTF-8
  </code></pre>
  
  <p>(this happens in both Chrome and Firefox).</p>
  
  <p>This leads me to think that the browser forces the header :)
  How can I circumvent this in Firefox?</p>