The Mozilla Application Framework: for powerful, easy to develop cross-platform applications

Want to build applications? Use the Mozilla framework and make your life easier. We provide a comprehensive framework that does much of the work for you, tools to help you develop your apps, and a community of people to help.


  • XUL: a comprehensive, cross-platform UI toolkit with an easy-to-learn XML language for defining UI structure, a schema for localization, and support for both native and cross-platform (using CSS) look and feel to make writing UIs quick and painless;
  • Gecko: a performant web content rendering/editing engine with world-leading support for standards that you can drop into your application with a single line of XUL;
  • Necko: a wicked-fast, extensible networking library with built-in support for many common protocols and a well-defined plug-in interface for custom protocol handling so you can add the protocols you need;
  • XPCOM: a simple, cross-platform component model with multiple language bindings and IDL descriptions so you can plug your custom functionality into the framework and connect it with other components;
  • Web Services: built-in support for XMLHttpRequest, XML-RPC, SOAP, and WSDL to enable Mozilla-based application authors to take advantage of the exploding world of web services;
  • XPInstall: our cross-platform installer for trivial packaging and installation of your Mozilla framework applications;
  • and much much more...


  • Venkman: a JavaScript debugger with support for breakpoints, conditional breakpoints, local variable inspection, watch variables, single step, stop on error, profile data collection, report generation, code reformatting (pretty printing), and more;
  • DOM Inspector: a tool for inspecting and editing the structure and widgets of your user interface while your application is running;
  • XULMaker: a GUI builder currently under development that lets you drag-and-drop widgets onto a grid to build your user interface;
  • Bugzilla: the Mozilla bug tracking webtool to help you track progress in fixing bugs and implementing features that affect your applications;
  • LXR: a web interface to the Mozilla codebase that shows you every file in the repository as well as a line-by-line breakdown of who changed which line when in each file
  • Bonsai: a web interface to the checkin log that you can query for checkins between certain dates, of certain files, or by certain developers;
  • Tinderbox: our 24/7 build and test webtool that constantly builds, tests, and reports on the Mozilla application suite on multiple platforms so you can see the state of the application at any given point in time.


  • a large, active development community that interacts via newsgroups, mailing lists, IRC channels, and web sites;
  • flexible licensing with three licenses to choose from (MPL, LGPL, and GPL) so you can develop both open source and proprietary applications and combine the Mozilla framework with other libraries;
  • dozens of existing applications from both large and small development teams;
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