Firebase Cloud Messaging

Firebase Cloud Messaging (FCM) is a cross-platform messaging solution that lets you reliably send messages at no cost.

Using FCM, you can notify a client app that new email or other data is available to sync. You can send notification messages to drive user re-engagement and retention. For use cases such as instant messaging, a message can transfer a payload of up to 4000 bytes to a client app.

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Key capabilities

Send notification messages or data messages	Send notification messages that are displayed to your user. Or send data messages and determine completely what happens in your application code. See Message types.
Versatile message targeting	Distribute messages to your client app in any of 3 ways—to single devices, to groups of devices, or to devices subscribed to topics.
Send messages from client apps	Send acknowledgments, chats, and other messages from devices back to your server over FCM’s reliable and battery-efficient connection channel.

How does it work?

An FCM implementation includes two main components for sending and receiving:

A trusted environment such as Cloud Functions for Firebase or an app server on which to build, target, and send messages.
An Apple, Android, or web (JavaScript) client app that receives messages via the corresponding platform-specific transport service.

You can send messages via the Firebase Admin SDK or the FCM server protocols. You can use the Notifications composer for testing and to send marketing or engagement messages using powerful built-in targeting and analytics or custom imported segments.

See the architectural overview for more detail and important information about the components of FCM.

Implementation path

	Set up the FCM SDK	Set up Firebase and FCM on your app according to the setup instructions for your platform.
	Develop your client app	Add message handling, topic subscription logic, or other optional features to your client app. During the development, you can easily send test messages from the Notifications composer.
	Develop your app server	Decide whether you want to use the Firebase Admin SDK or one of the server protocols to create your sending logic—logic to authenticate, build send requests, handle responses, and so on. Then build out the logic in your trusted environment. Note that if you want to use upstream messaging from your client applications, you must use XMPP, and that Cloud Functions does not support the persistent connection required by XMPP.

Next steps

Run the Android or iOS Quickstart sample. These samples let you run and review code to send a test message to a single device using the Firebase console.
Try the tutorials for Android or iOS.
Add Firebase Cloud Messaging to your Android, Apple, or Web app.
Set up your trusted environment where you'll build and send message requests. You can write sending logic using the Admin SDK, and readily deploy that code on Cloud Functions for Firebase or other cloud environments managed by Google. Alternatively, you can perform server development using the FCM server protocols.
Learn more about sending data payloads, setting message priority, and other messaging options that are available with FCM.