Reduce Delays from Expect: 100-continue headers

To have Fiddler return the 100-Continue header for a request:

  1. Click Rules > Customize Rules....

  2. Add the following function inside the Handlers class:

    static function OnPeekAtRequestHeaders(oSession: Session) {
       if (oSession.HTTPMethodIs("POST") && oSession.oRequest.headers.ExistsAndContains("Expect", "continue"))
       {
         if (null != oSession.oRequest.pipeClient)
         { 
           oSession["ui-backcolor"] = "lightyellow";
           oSession.oRequest.headers.Remove("Expect");
           oSession.oRequest.pipeClient.Send(System.Text.Encoding.ASCII.GetBytes("HTTP/1.1 100 Continue\r\nServer: Fiddler\r\n\r\n")); 
         } 
       }
    }