I need to do some testing of the REST service from Firefox, where I set the Content-Type HTTP header to a specific value (to extract XML or JSON).
Is there a Firefox add-on that can do this?
There Modify Headers "... You can change the user-agent line, add headers to fake a request for mobile (for example, x-up-call-line-id) ..."
https://addons.mozilla.org/en-US/firefox/addon/967