Methods, systems, and apparatus, including medium-encoded computer program products, for managing an application execution environment on a computer. One or more aspects of the subject matter described in this specification can be embodied in one or more methods of managing an application execution environment comprising a cross-platform application program interface to provide services to applications that run in the application execution environment, the one or more methods including: maintaining associations between the applications and different versions of the application execution environment installed on a computer, where the associations indicate in which of the different versions of the application execution environment the applications run; and managing the different versions of the application execution environment on the computer based on the associations between the applications and the different versions of the application execution environment in which the applications run.