Push Notifications definition
Push notifications are short messages that a server sends to a user's device through the operating system's notification service, appearing even when the app is not open. On mobile they are delivered through Apple Push Notification service (APNs) and Firebase Cloud Messaging (FCM), and browsers support web push for websites and progressive web apps.
How do push notifications work?
Apps never connect to phones directly. Each platform runs a push service that keeps one efficient connection to every device, and app backends send messages through it. The flow is the same on iOS, Android and the web, with small differences in authentication and payload format.
- The app asks the user for permission to show notifications.
- The operating system registers with APNs or FCM and returns a device token.
- The app sends that token to your backend, linked to the user's account.
- Your server sends a message with the token to APNs or FCM over their HTTP APIs.
- The push service delivers it, and the operating system displays it.
- A tap opens the app, ideally on the exact screen the message refers to.
Types of push notifications
Tokens change when apps are reinstalled or restored, and they become invalid when users uninstall, so backends must update tokens on every launch and remove ones the push service rejects. Sending to stale tokens wastes resources and skews delivery metrics.
- Transactional: order confirmations, delivery updates, security alerts.
- Behavioral: reminders triggered by actions, such as an abandoned cart.
- Promotional: offers, launches and campaigns.
- Silent or background: wake the app to sync data without showing anything.
- Rich: images, action buttons and expandable content.
- Web push: notifications from websites and PWAs through the browser.
Permissions and platform rules
iOS has always required users to opt in, and Android 13 introduced a runtime notification permission as well, so apps on both platforms must earn permission. Asking on first launch, before users see any value, leads to refusals that are hard to reverse. A better pattern explains the benefit on a custom screen first, then shows the system prompt at a relevant moment, such as after placing the first order.
Android notification channels let users switch categories on or off, such as promotions versus delivery updates, and iOS offers provisional authorization for quiet delivery and interruption levels for time-sensitive alerts. Respecting these controls keeps users from disabling notifications entirely. Each category should earn its place.
Push notification best practices
- Send messages that are useful to the individual, not the same blast to everyone.
- Cap frequency and respect time zones and quiet hours.
- Deep link every notification to the relevant screen.
- Localize content and keep the first line meaningful on its own.
- A/B test copy and timing, and track opens, conversions and opt-outs.
- Never put sensitive personal data in the visible text.
- Group related notifications instead of sending many in a row.
Tools for sending push notifications
Teams can call APNs and FCM directly or use services that add segmentation, scheduling and analytics, such as OneSignal, Braze, Airship or Expo Notifications for React Native apps. Nexzem implements push notifications with token management, user preference centers and deep links built in, and connects them to the client's CRM or marketing platform so messages follow real customer behavior.