Push Notifications

Push notifications are short messages that a backend server delivers to a user's device through the OS-level push service, displayed even when the corresponding app is not running. Push is the standard re-engagement and real-time messaging channel on mobile and increasingly on web.

How it works

The app registers with the OS push service (APNs on iOS, FCM on Android, Web Push on browsers) and receives a unique device token. The token is sent to the backend, which stores it against the user. To deliver a push, the backend posts a message to the platform service with the token; the service delivers the payload to the device, which renders the notification or wakes the app to handle it silently.

Common platform services

• APNs (Apple Push Notification service). iOS, iPadOS, macOS, watchOS, tvOS.
• FCM (Firebase Cloud Messaging). Android, iOS, web; the most common cross-platform option.
• Web Push. W3C standard supported by most browsers; iOS added support in 16.4+ for installed PWAs.
• OneSignal, Airship, Braze, Customer.io. Higher-level providers that orchestrate APNs, FCM, Web Push, SMS, and email.

Notification types

• Alert / banner. Visible to the user with title, body, icon, action buttons.
• Silent / data. Delivered to the app to trigger background processing without showing the user anything.
• Rich. Include images, video, custom layouts (Notification Service Extension on iOS, NotificationCompat.BigPictureStyle on Android).
• Live Activities and widgets. Persistent, dynamically updated notifications on the lock screen and Dynamic Island (iOS).