The present invention relates to a method for dynamically modifying the user interface of a deployed application. The method including: a deployed application executing on a user device in accordance with pre-stored configuration data to provide at least part of the user interface; and the deployed application receiving modified configuration data from a server. The at least part of the user interface may be modified in accordance with received modified configuration data. The present invention also relates to a method for dynamically modifying the user interface of a deployed application. The method includes a deployed application executing on a device in accordance with pre-stored configuration data to provide at least part of the user interface; and the deployed application modifying at least part of the user interface in response to user input. The at least part of the user interface may be user interface navigation data. A user device and system are also disclosed.