Now Fiddler has a limitation about maintaining its own cookie jar. When I use Composer to do a POST request simulation, if this request get a 302 response and Set-Cookies, Fiddler will automaticly redirected to the next page, but the cookies are all lost. And PostMan works well in this situation. Refer to Google Group to see the details of this issue: https://groups.google.com/forum/?fromgroups=#!topic/httpfiddler/vn1du8QdAVk