An in-vehicle system enables retrofitted hardware to be used in cases in which predetermined hardware has been connected to an in-vehicle unit by performing processing to obtain an application corresponding to the predetermined hardware from a server and install the application in the in-vehicle unit. In cases in which the retrofitted hardware has been disconnected from the in-vehicle unit, the in-vehicle system also performs at least one type of processing out of processing to compress or processing to delete the application corresponding to the retrofitted hardware that has been disconnected.