Welcome to the Jetpack Project! Jetpack's mission is to make it easy to create add-ons for Firefox using the languages of the web—HTML, CSS, and JavaScript. Right now the project is developing one product: the Add-on SDK. The Add-on Builder is now in read-only mode and will be turned off completely in April 2014. Please download your data before then. Learn more. The Add-on SDK is a locally-hosted