Charles is a HTTP proxy that enables you to see traffic between your machine and the backend

Free browser plugin to measures page load time and displays it in the toolbar.

Vigil is an open-source Status Page you can host on your infrastructure, used to monitor all your servers and apps, and visible to your users.

Hosted System Status Pages Fully customizable, featuring incident tracking, subscriber notifications, and much more

Simplifies performance and load testing so that application delivery teams can take a standardized approach to ensure continuous performance, reliability, and scalability from development to production.

Percy is a visual testing and monitoring tool that focuses on detecting visual changes in web applications