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Extensions are small add-ons that add new functionality to Mozilla applications such as Firefox and Thunderbird. They can add anything from a toolbar button to a completely new feature. They allow the application to be customized to fit the personal needs of each user if they need additional features, while keeping the applications small to download.

Extension Frequently Asked Questions

Common questions and answers about extension development.

Setting up extension development environment

A few essential setup tips that make extension development easier.

Extension Packaging

How to package your Firefox extension for downloading and installation.

Creating Custom Firefox Extensions with the Mozilla Build System

How to set up the build environment for an extension that makes use of binary components.

Adapting XUL Applications for Firefox 1.5

A list of changes in Firefox 1.5 that affect XUL developers.

XPCNativeWrapper

Limits access to the properties and methods of the object it wraps, allowing safe access to the IDL-defined methods of the object.

Code snippets

Code commonly used by many extensions. See also articles in Category:Extensions for more examples

From Mozilla Developer Center