API Reference > imodeljs-frontend > Extensions Extensions Classes for creating and managing runtime Extensions Classes Name Description Extension Base Extension class for writing a demand-loaded module. Beta ExtensionAdmin Handles the loading of Extensions, and maintains a list of registered, currently loaded, and currently being downloaded extensions. Beta ExtensionServiceExtensionLoader Downloads extensions from Extension Service Beta ExternalServerExtensionLoader Reads the extension from a plain server assuming that the extension is a set of files in a directory formatted as: Beta PendingExtension Represents an Extension that we are attempting to load. Beta Interfaces Name Description ExtensionAdminProps Describes configuration options to the ExtensionAdmin Beta ExtensionLoader Implement this interface, then register it using IModelApp.extensionAdmin.addExtensionLoader to load extensions from a different source. Beta Last Updated: 29 November, 2022