Developing add-ons

Mozilla based software is typically extensible through add-ons. There are three primary types of add-on: extensions, plugins, and themes. This page will help guide you to the information you need in order to create add-ons for Firefox, Thunderbird, or other software based on the Mozilla platform, as well as how to distribute your add-ons.

Add-ons topics

Submitting an add-on to AMO
Provides helpful information for add-on developers to help them properly package and deliver their add-ons. This includes information about, Mozilla's add-on distribution web site.
Extensions add new functionality to Mozilla applications such as Firefox, SeaMonkey and Thunderbird. They can add anything from a toolbar button to a completely new feature.
Information about how to create plugins, which are binary components that let Mozilla based software display content they can't handle natively.
Browser extension development for everyone. Jetpack developers only need to know the tools of the modern web: HTML, CSS, and JavaScript.
Themes let users customize the appearance of the user interface presented by Mozilla-based applications.
Search engine plugins
Firefox supports search engine plugins, which enable the search box to support different search engines. (AMO) API Developers' Guide
The AMO Developers' Guide describes how to use the AMO API to fetch information about add-ons from the site.
The Mozilla platform
Information about the Mozilla platform, including all of its APIs and technologies, as well as how to use them in your own projects.
Performance guides and utilities to help you make your add-on perform well (and to play nicely with others).