UXsniff - Track user behavior on your website and improve conversions with UXsniff: the user experience watchdog that looks out for you.
Fiddler - Fiddler is a debugging program for websites.
Rage Grade by FullStory - Benchmark your customer frustration
Proxyman.io - Proxyman is a high-performance macOS app, which enables developers to view HTTP/HTTPS requests from apps and domains.
Talebook - Understand your client and kick-off your new project!
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.