An interactive console program that allows traffic flows to be intercepted, inspected, modified and replayed.
restc is an HTTP server middleware, aiming to enhance debugging experience on RESTful APIs.
debugs memory leak of running process, without recompiling or restarting, on GNU/Linux and FreeBSD
Web Debugging Proxy based on Chrome DevTools Network panel.
An open source, extensible, platform-agnostic tool for remotely debugging and testing your JavaScript. Powered by node.js and socket.io.
MailCatcher runs a super simple SMTP server which catches any message sent to it to display in a web interface. Run mailcatcher, set your favourite app to deliver to smtp://127.0.0.1:1025 instead of your default SMTP server, then check out http://127.0.0.1:1080 to see the mail that's arrived so far.
jQuery-inlog allows you to easily debug your jQuery code. See exactly what you pass to functions, what they return and in which context (this-value) they were executed.
The DebugBar integrates easily in any projects and can display profiling data from any part of your application. It comes built-in with data collectors for standard PHP features and popular projects.
Helium is a tool for discovering unused CSS across many pages on a web site. The tool is javascript-based and runs from the browser.
whoops is a nice little library that helps you develop and maintain your projects better, by helping you deal with errors and exceptions in a less painful way.
Holmes is stand-alone diagnostic CSS stylesheet that can highlight potentially invalid or erroneous HTML(5) markup by adding one class — Read more