What is Firebase Cloud Messaging (FCM)?
Answer
Firebase Cloud Messaging (FCM) is Google's free, reliable messaging service for sending push notifications to Android, iOS, and web applications. It replaced Google Cloud Messaging (GCM) in 2016. FCM sends two types of messages: (1) Notification messages — displayed in the system notification tray automatically (no app code needed); (2) Data messages — delivered to the app code for custom handling. FCM features: Topic messaging — broadcast to all devices subscribed to a topic (e.g., "sports-news"); Device group messaging — send to all devices owned by a user; Downstream messaging — from your server to devices; Analytics integration — track notification open rates. Use cases: order updates, social notifications, breaking news alerts, reminders. FCM is free with no per-message cost, making it practical for high-volume notification systems. The Firebase Admin SDK enables server-side notification sending from Node.js, Java, Python, Go, and C#.