A facility is provided for managing application customization. In various embodiments, an application associated with the facility receives an indication of an application identifier that identifies a customized instance of the application, determines whether the customized instance of the application is available and, when the customized instance of the application is available, configures the application to employ a resource associated with the customized instance of the application. The facility can receive an identifier and an indication to update common components of an application, the application having a customized instance of the application; remove components associated with the customized instance of the application; copy common components associated with the application; associate the common components with the received identifier; and apply customizing components that customize the common components of the application to create a customized instance of the application.