When a TRACE method is used, the receiving server bounces back the TRACE response with the original request message in the body of the response. The TRACE method is used to identify any alterations to the request by intermediary devices such as proxy servers and firewalls. Some proxy servers edit the HTTP header when the packets pass through it, and this can be identified using the TRACE method. It is used for testing purposes, as it lets you track what has been received by the other side.