🧠 FCM Token & Expo Token (Push Notifications)
I use FCM tokens and Expo tokens to send push notifications to mobile or web applications.
🎯 Simple Idea
To send a notification to a specific device:
👉 each device must have a unique token
FCM Token → used with Firebase Cloud Messaging
Expo Token → used with Expo (React Native)
🧩 FCM Token
generated by Firebase SDK on the client
uniquely identifies a device/app instance
Used for:
Android, iOS, and web push notifications
Flow:
1. app requests permission
1. device receives FCM token
1. token is sent to backend
1. backend sends notification using that token
🧩 Expo Token
generated by Expo Notifications API
wraps FCM/APNs internally
👉 easier setup for React Native apps using Expo
Flow:
1. app gets Expo push token
1. token sent to backend
1. backend sends notification via Expo service
🧠 Why I Use This
target notifications to specific users/devices
support real-time alerts (messages, updates)
improve user engagement
⚖️ Tradeoff Awareness
tokens can expire or change → must update regularly
need to manage multiple tokens per user (multiple devices)
requires handling notification permissions
📌 Practical Rule
> always store and update device tokens correctly
💬 Summary
I use:
FCM Token → direct push notification system
Expo Token → simplified layer for mobile apps
👉 to deliver reliable and targeted notifications 👍