Trace - Visualized Node.js monitoring
Charles Proxy - HTTP proxy / HTTP monitor / Reverse Proxy
WeBlock - Weblock allows you to block online content.
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.
SponsorBlock - SponsorBlock is an open-source crowdsourced browser extension to skip sponsor segments in YouTube videos.
Weer - A HTTP protocol debugger with Chrome DevTools frontend interface