1. A computer-implemented method performed by data processing apparatus comprising one or more computers in data communication, the method comprising: determining, for a native application that generates an application environment for display on a user device within the native application, the native application operating independent of a browser application that can operate on the user device, a set of environment instances of the native application; for each environment instance: determining textual data describing features of the corresponding environment instance, the textual data being data that is not rendered to be visible when the native application renders the environment instance on a user device display; generating, from the textual data, native application environment instance data describing content of the environment instance; and indexing the native application environment instance data for the native application in an index that is searchable by a search engine.