Following document, https://developer.apple.com/library/archive/documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/HandlingRemoteNotifications.html has a desription, "If the device token changes while your app is running, the app object calls the application:didRegisterForRemoteNotificationsWithDeviceToken: delegate method again to notify you of the change.", and you can read it so that the device token may be updated while the application is running. However, since this article is from 2018, I think it may not happen on newer versions of iOS. We would appreciate it if you could teach us the specifications for updating the device token. Best regards,