Proxyman.io - Proxyman is a high-performance macOS app, which enables developers to view HTTP/HTTPS requests from apps and domains.
Fiddler - Fiddler is a debugging program for websites.
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.
Replay - One-Click Video Editor for iOS
Reactime - Time travel debugging tool, visualizing and tracing state
mitmproxy - mitmproxy is an SSL-capable man-in-the-middle proxy for HTTP.