1. A method performed by a computing system for managing application customization, comprising: receiving an application identifier for an application and an indication to update common components of the application, the application having a customized instance of the application; removing components associated with the customized instance of the application; copying common components associated with the application; associating the common components with the received identifier; applying customizing components that customize the common components of the application to create a customized instance of the application; receiving a first identifier with an indication to start the customized instance of the application corresponding to the first identifier; starting the customized instance of the application; receiving a second identifier with an indication to start another customized instance of the application corresponding to the second identifier wherein the other customized instance of the application is different from the customized instance of the application; and starting the second customized instance of the application wherein the customized instance of the application and the other customized instance of the application both execute the common components but provide different functionality.