Charles Proxy is exactly what its name implies; a proxy. This proxy is special however, as it is specifically aimed at giving functionality that developers will need. It allows you to view, change and replay the traffic that passes through, and can handle SSL. Charles isn't free, but at $50 (at the time of writing) for a license, it reaps returns from day one. This article will show you how to start using Charles and covers techniques that will help you work with your web and mobile applications; basically anything that works over HTTP.