Surge for Mac - Advanced Web Debugging Proxy for Mac & iOS
Google Chrome Developer Tools - Get started with Google Chrome's built-in web developer tools.
Weer - A HTTP protocol debugger with Chrome DevTools frontend interface
Omnibug - Omnibug is a plugin for the Google Chrome and Mozilla Firefox browsers to ease developing and...
Charles Proxy - HTTP proxy / HTTP monitor / Reverse Proxy
Fiddler - Fiddler is a debugging program for websites.