Charles Proxy - HTTP proxy / HTTP monitor / Reverse Proxy
Proxyman.io - Proxyman is a high-performance macOS app, which enables developers to view HTTP/HTTPS requests from apps and domains.
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.
Weer - A HTTP protocol debugger with Chrome DevTools frontend interface
Replay - One-Click Video Editor for iOS
Reactime - Time travel debugging tool, visualizing and tracing state