Developer's DescriptionBy Mozilla LabsCreate powerful Firefox add-ons using just HTML, CSS, and JavaScript.Add-on Builder provides powerful APIs and tools that allow developers to create add-ons for Firefox using HTML, CSS and JavaScript. When your add-on is complete, we make it easy to share it with over 400 million Firefox users world wide.The Add-on Builder is a web-based development environment that provides additional functionality for working with the Add-on SDK.Edit code in a feature-rich environment, test your add-ons instantly, and use built-in version control & sharing.