Handling the requests and responses that are inherent to the Hypertext Transfer Protocol (HTTP) is a delicate task. Viewing and modifying anything related to this protocol is a highly specialized job that not only requires solid knowledge, but also a particular kind of utility.
Once of the simpler methods of attaining the above mentioned goal, especially of you are using Mozilla's Firefox web browser, is a tiny extension that goes by the name of Tamper Data. It is designed to help you do exactly the already referenced tasks.
Thus, with the help of Tamper Data, you should be able to check out the headers and POST parameters of HTTP as well as HTTPS protocols. This lightweight add-on is also able to provide editing functions you can use to manually change the data.
As soon as you install and activate the extension, you will gain access to a lot of information that is otherwise unavailable. For instance, you can view details regarding the ongoing requests and see each request and response header name, alongside other data.
The Firefox add-on is able to display the host and user agent, as well as the accept language, character set (charset) and encoding. Keep alive, connection and HTTP referer are also included in the list of details presented by Tamper Data.
There is also an 'Options' menu that is worth checking out, especially since it allows you to view and modify context menu entries. You can add new ones or remove exiting items and the same applies to their labels which can also be modified.
Everything you modify in the 'Options' area of Tamper Data can be exported and if you wish to restore some older settings that you saved, the 'Import' function will surely help.
All things considered, if you are on the look out for a utility that can trace HTTP as well as HTTPS responses and requests, while providing the means to edit headers and POST parameters, Tamper Data is definitely worth a closer look.