UserTesting.com - Usability testing has never been easier. Get videos of real people speaking their thoughts as they use websites, mobile apps, prototypes and more!
Fiddler - Fiddler is a debugging program for websites.
Instabug - The top apps in the world rely on Instabug for beta testing, user engagement and crash reporting.
Proxyman.io - Proxyman is a high-performance macOS app, which enables developers to view HTTP/HTTPS requests from apps and domains.
Userbrain - Easy, fast, and affordable user testing for websites and prototypes.
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.