The following is a list of tools and resources that will help with your web development process, as well as potentially debugging your Firefox browser add-ons.

Web development

Integrated into Firefox

Tools and resources that are built into Firefox and are in heavy development.

Scratchpad Requires Gecko 6.0
A text editor built into Firefox that lets you edit and run JavaScript code.
Web Console Requires Gecko 2.0
A console that lets you interactively output information, run JavaScript snippets, and experiment with your content.
Page Inspector Requires Gecko 10.0
A useful tool that shows you the HTML of the element you're currently pointing at with your mouse, in context.
Style Editor Requires Gecko 11.0
Lets you edit CSS styles for the current page in real time; in addition, you can toggle them on and off. A fantastic way to work in real time with the look and feel of web content!
Using the Source Editor
The Source Editor isn't a standalone tool; instead, it's the underlying editor used by Scratchpad and the Style Editor. This article provides information common to all tools that make use of the Source Editor API.
Graphic Command Line Interface Requires Gecko 12.0
GCLI provides a command-line interface to manipulate and work with the developer tools in Firefox.


JavaScript debugger provides a powerful JavaScript debugging environment for Mozilla based browsers.
DOM Inspector
A developer tool used to inspect, browse, and edit the DOM of documents - usually web pages or XUL windows.
Integrates a wealth of development tools to edit, debug, and monitor CSS, HTML, and JavaScript live in any web page (details)
Web Developer
Adds a menu and a toolbar to the browser with various web developer tools. (details)
Reveals DOM elements as you scrub the mouse over a page. (details)
More on Firefox Add-ons
Web development category in the Firefox Add-ons site


List of validators
Various validators for things like HTML, CSS, RDF, Firefox extensions, and many others.

Authoring Software

Tool used to fix or point out invalid HTML as well as improve the layout and indentation style of the resulting markup.


Error Console
Tool used for reporting errors in the application chrome and user-opened web pages. Also reports JavaScript-related errors and warnings, CSS errors and arbitrary messages from chrome code.
Mozilla's JavaScript Debugger
JavaScript Code Quality Tool
Tool used for generation of (usually HTML) documentation from code comments (similar to JavaDoc).


DOM Inspector
Developer tool used to inspect, browse, and edit the Document Object Model of documents
Mouseover DOM Inpector is a bookmarklet that allows you to view and manipulate the DOM of a web page simply by mousing around the document.


Localization and Leveraging Tools
Tools and resources to help localize and translate your extensions to other languages.



WAI-ARIA Overview
An overview of WAI-ARIA, the Accessible Rich Internet Applications Suite; a set of documents that lay out how to make Web 2.0 sites and applications more accessible.

Testing Tools

AChecker is a tool that allows you to type in a url and test for accessibility.
W3C complete list of tools
A Complete list of web accessibility evaluation tools

A more comprehensive list of accessibility resources, see: Fluid Project accessibility resources and ARIA

Tree and branch management

cross-commit script
Concurrent Versions System(CVS) script that allows a single patch to be easily checked in on multiple branches.

User profile tools

Multiple Firefox profiles

Navigating the Mozilla Codebase

MXR (if you use vim, mxr-vim speeds up the process)


Profile Manager

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