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
More specifically, the limitation in question is that Fiddler does not keep a Cookie jar for its Composer. It shouldn't be terribly hard to add a basic one (using the classes in the .NET framework will work for most cookies, see the code in TestStudio); the only question is whether it should last longer than a single transaction. If not, then the user needs a mechanism to clear it.