Fiddler - Fiddler is a debugging program for websites.
Mac CLi - OS X command line tools for developers
Proxyman.io - Proxyman is a high-performance macOS app, which enables developers to view HTTP/HTTPS requests from apps and domains.
Phunt - Product Hunt command line interface
HTTP Toolkit - Beautiful, cross-platform & open-source tools to debug, test & build with HTTP(S). One-click setup for browsers, servers, Android, CLI tools, scripts and more.
speedtest-cli - Test your download speed using SpeedTest on the command-line