nginx - A high performance free open source web server powering busiest sites on the Internet.
Charles Proxy - HTTP proxy / HTTP monitor / Reverse Proxy
Cilium - API-aware Networking and Security
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.
Big Cloud Fabric - Data Center Networking
Weer - A HTTP protocol debugger with Chrome DevTools frontend interface