Technology for interoperability is disclosed by enabling the sharing of application state data for an application experience across computing devices, operating systems, applications, or locations. In one aspect, a secondary application shares encrypted state data along with a non-encrypted hint that describes the application experience reflected in the state data with a primary application. The primary application is then able to use the hint to determine that a user is interested in returning to the experience in the secondary application. The primary application then transfers the encrypted state data to the secondary application which uses the state data to return the application to the application experience. A platform and application programming interface (API) are provided for computer applications and services to store and retrieve application state data associated with an event.