Google Chrome Developer Tools is described as 'The Google Chrome Developer Tools provide an integrated environment for debugging, optimizing, and understanding a web application, or website, running in Google Chrome. The developer tools are developed partly through the WebKit open source project, where the tools are called' and is a very popular Web Debugger in the development category. There are more than 10 alternatives to Google Chrome Developer Tools for a variety of platforms, including Windows, Linux, Mac, Web-based and Mozilla Firefox apps. The best Google Chrome Developer Tools alternative is Firefox Developer Tools, which is both free and Open Source. Other great apps like Google Chrome Developer Tools are Web Developer, HttpWatch, HTTP Debugger and Omnibug.
DOMScope is an online web inspector and debugger for mobile web apps. Like Chrome's DevTools, it allows developers to navigate through the HTML, list applied CSS styles and execute JavaScript code inside any device's browser.
Test HTML / JavaScript / CSS snippets with real-time preview. You could also add libraries (jQuery, YUI etc.).
Venkman is the code name for Mozilla's JavaScript Debugger. Venkman aimed to provide a powerful JavaScript debugging environment for Mozilla based browsers.
Uthrottle is a tool which simulates custom connection’s conditions and limits the network traffic to a specified speed on network interfaces. In complex service oriented application stacks, some bugs only manifest themselves on congested or slow
