Charles is described as 'HTTP proxy / HTTP monitor / Reverse Proxy that enables a developer to view all of the HTTP and SSL / HTTPS traffic between their machine and the Internet. This includes requests, responses and the HTTP headers (which contain the cookies and caching information)' and is a popular http(s) debugger in the development category. There are more than 25 alternatives to Charles for a variety of platforms, including Mac, Windows, Linux, iPhone and iPad apps. The best Charles alternative is mitmproxy, which is both free and Open Source. Other great apps like Charles are Fiddler, HTTP Toolkit, Burp Suite and Proxyman.