httpbin(1) - HTTP request and response service
Smart HTTPS - Automatically changes HTTP addresses to the secure HTTPS, and if loading encounters error, reverts...
HTTPDump - A simple, beautiful Webhook debugging tool.
SSL Enforcer - SSL Enforcer - Force SSL/TLS encryption for any browser or app. Block all unsecure connections.
Proxyman.io - Proxyman is a high-performance macOS app, which enables developers to view HTTP/HTTPS requests from apps and domains.
HTTPZ - HTTPZ is meant to be unobtrusive and lightweight.