Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for extending application access across devices. In some implementations, an electronic device receives a request to provide access to the electronic device to a particular user that is not registered as a user of the electronic device. The electronic device receives authentication credentials for the particular user. The electronic device provides the authentication credentials to a server system and receives data from the server system that (i) indicates that the providing access to the electronic device in a guest mode is authorized, and (ii) indicates a state of an instance of an application installed on a second device. The electronic device provides access to the electronic device in the guest mode that provides an interface that at least partially recreates the state of the instance of the application installed on the second device.