Push Notifications

Two kinds of notification

A notification is the banner that appears on the lock screen or at the top of the phone, even when your app is closed. There are two kinds, and it helps to keep them straight:

• Local notification — your app schedules it on the device itself (e.g. "remind me in 1 hour"). No server needed.
• Remote / push notification — a server sends it to the phone over the internet (e.g. "you have a new message"). This is what most people mean by "push".

Expo wraps both in one module, expo-notifications, and runs a free service that delivers remote pushes to Android and iOS without you wiring up each platform’s system separately.

Install it (one-time):

npx expo install expo-notifications

Step 1 — Ask permission and get a push token

Like the camera, notifications need permission first. For remote push you also need this phone’s push token — a unique address the server uses to reach this exact device. You ask for both together:

import * as Notifications from 'expo-notifications';

async function registerForPush() {
  const { status } = await Notifications.requestPermissionsAsync();
  if (status !== 'granted') {
    console.log('Notifications not allowed');
    return null;
  }
  const token = (await Notifications.getExpoPushTokenAsync()).data;
  console.log('Push token:', token);
  return token;   // send this to your server
}

Step 2 — Schedule a local notification

A local notification is the simplest to try because it needs no server — you schedule it right on the device. Here we fire one 5 seconds from now:

await Notifications.scheduleNotificationAsync({
  content: {
    title: 'Time to study! 📚',
    body: 'Open Code Kaksha and finish today’s lesson.',
  },
  trigger: { seconds: 5 },
});

How a remote push reaches the phone, step by step

Remote push has more moving parts. Here is the whole journey, in order, so the pieces make sense:

1. On first launch the app calls requestPermissionsAsync(); the user taps Allow.
2. The app gets its push token with getExpoPushTokenAsync() — this device’s unique address.
3. The app sends that token to your server, which stores it next to the user’s account.
4. Later, something happens worth notifying about (a new message). Your server asks Expo’s push service to deliver a notification to that token.
5. Expo hands the notification to Apple’s or Google’s system, which shows the banner on the phone — even if your app is closed.
6. When the user taps the banner, your app opens (and with deep linking from the earlier lesson, can jump straight to the relevant screen).