Seems to have a bug Rated 4 out of 5 stars
I find this very useful as an add on.
RESTClient: getResource INFO:NS_ERROR_FAILURE: Component returned failure code: 0x80004005 (NS_ERROR_FAILURE) [nsIXMLHttpRequest.setRequestHeader]
I sent a post request to some URL after adding the below headers:
The request never reaches server.
However If I initially post the request with some other header name like ABCD and then edit the header name to X-CT-DOMAIN then it works.