Proxyman.io - Proxyman is a high-performance macOS app, which enables developers to view HTTP/HTTPS requests from apps and domains.
Charles Proxy - HTTP proxy / HTTP monitor / Reverse Proxy
Endpoints - View and respond to requests on an HTTP endpoint
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.
httpbin(1) - HTTP request and response service
Weer - A HTTP protocol debugger with Chrome DevTools frontend interface