The goal of this work is to provide users immersed in a multi-platform environment with the possibility of interacting with an application while freely moving from one device to another. We describe the solution that we have developed for a service to support platform-aware runtime migration for Web applications. This allows users interacting with an application to change device and continue their interaction from the same point. The service performs the migration of the application taking into account its runtime state and adapting the application interface to the features of the target platforms. The service is optimized for applications developed through a modelbased, multiple-level approach. The intelligence of the adaptive interfaces resides in the migration server, which adapts data collected at runtime from their original format to the format best fitting the features of the target platform. We also indicate how it is possible to extend this result in order to support partial migration and synergistic access, by which a part of the user interface is kept on one device during runtime and the remaining part is moved to another with different characteristics.