Charles is a web proxy (HTTP Proxy / HTTP Monitor) that runs on your own computer. Your web browser (or any other Internet application) is then configured to access the Internet through Charles, & Charles is then able to record & display for you all of the data that is sent & received.
In Web & Internet development you are unable to see what is being sent & received between your web browser / client & the server. Without this visibility it is difficult & time-consuming to determine exactly where the fault is. Charles makes it easy to see what is happening, so you can quickly diagnose & fix problems.
Charles makes debugging quick, reliable & advanced; saving you time & frustration!
SSL Proxying - view SSL requests & responses in plain text
B&width Throttling to simulate slower Internet connections including latency
AJAX debugging - view XML & JSON requests & responses as a tree or as text
AMF - view the contents of Flash Remoting / Flex Remoting messages as a tree
Repeat requests to test back-end changes
Edit requests to test different inputs
Breakpoints to intercept & edit requests or responses
Validate recorded HTML, CSS & RSS/atom responses using the W3C validator
The following features are what I believe to be the key features of Charles. The best way to explore these features & to discover others is to download the free trial.
Charles can act as a man-in-the-middle for HTTP/SSL communication, enabling you to debug the content of your HTTPS sessions.
Charles simulates modem speeds by effectively throttling your b&width & introducing latency, so that you can experience an entire website as a modem user might (b&width simulator).
Charles is great for Adobe Flash developers as you can view the contents of LoadVariables, LoadMovie & XML loads. Charles also has native support for Flash Remoting (AMF0 & AMF3).
Autoconfigure Browser & System Proxy Settings
Charles will autoconfigure your browser's proxy settings on the following browsers:
Windows system proxy settings (includes Internet Explorer & most other applications)
Mac OS X system proxy settings (includes Safari & most other applications)
Mozilla Firefox (on all platforms)
Home Page - http://www.charlesproxy.com