Charles is a web proxy that works as an HTTP and HTTPS data analyzer. It gets located in the middle of the client/server communication. This allows you to analyze, record, and debug the traffic created. As of version 3.1, it can be used as a basic SOCKS proxy too.
It is user friendly and navigating through its windows and panels is easy. It automatically configures the settings of your web browsers and starts recording sent and received data.
You can visualize data in a structured way or as a sequence. It supports HTTPS, which lets you view data unencrypted. You can also set breakpoints, which let you intercept and modify data as it passes through. You can also export and import sessions to different formats.
This is a useful tool for webmasters wishing to analyze how their site is performing before going online, specially when it comes to the server program. You can modify some headers to see how the server behaves in different scenarios so you can determine some of the causes of error.
Unfortunately, it showed some errors while working with SSL proxying function. This works as a man-in-the-middle attack and is used to analyze the secure traffic unencrypted. Some connections failed to establish.
Most people make use of this application to cheat in online games by catching the score before it is sent to the server and then modifying the corresponding value for a higher one. Once done, data is sent to the server, which processes the information as it would normally do and the user gets his score displayed in the list of top scores.
Since this application is written in the Java programming language, it needs the JRE (Java Runtime Environment) installed, otherwise you will get an error message when trying to run it. It is important to remark that if you wish to run the x64 version of Charles, you need to have the 64-bit version of the JRE.
Even though it is a Java application, which requires the code to be interpreted and compiled on the fly, it performs fast and doesn't delay the communications between server and browser. And with minor issues, it can be a very useful tool for both experienced and non-experienced users web users.