(Note: DO NOT enter your real password. Everyone can see it.)

Detailed on my blog: Ajax with FormData is Broken on IE10 / IE11 in Some Conditions


  1. Open http://requestb.in/10voz8j1?inspect, the request will be sent to here.
  2. Leave the last checkbox unchecked, and click "Sign Up" in the form above.
  3. In IE10 and IE11, the request body will be corrupted.
  4. Check the last checkbox and send the form again. This time the request body will be correct.

You can change action attribute of the form to send to a web server running in localhost and eavesdrop the request in a local proxy software like mitmproxy or Fiddler.


Add a hidden input with arbitrary name at the end of form, to make the original checkable input not the latest one.

I've opened a bug on IE Feedback.

Author: @yorkxin; Original Bin: http://jsbin.com/muqem/latest