Jetpack is a project that develops tools and frameworks to ease development of Firefox add-ons. The project has produced the Add-on SDK, a set of APIs, a runtime, and a command-line tool for creating and running add-ons, and the Add-on Builder, a Web-based integrated development environment which uses the SDK.Add-ons developed with the SDK are written in HTML, CSS, and JavaScript using CommonJS conventions. They do not require the user to restart Firefox when they are installed and uninstalled.