Charles is an HTTP proxy, monitor, and reverse proxy that lets developers view HTTP and SSL traffic from their machines. Web browsers access the internet through this software so that users can diagnose excess traffic and fix the problem.
Regarding time efficiency, debugging is as fast and reliable as possible.
Features include SSL Proxying, useful to view SSL requests in plain text; bandwidth throttling simulating latency and other slow connection malfunctions; AJAX debugging; AMF displaying contents of Flash Remoting or Flex Remoting as a tree.
Back-end changes can be tested through repeated requests. Different inputs are also verifiable by editing requests. HTML, CSS, and RSS responses are validated using the W3C checker.
Every feature comes out of the box, with system and browser proxy settings auto-configured.