In 2009, Apple introduced push notifications with the release of iOS 3.0. Suddenly, messages could be sent to mobile devices, computers, or desktops, even when customers were not running any application!

Later, Google introduced the Android Cloud to Device Messaging (C2DM) service to compete with Apple’s services. However, this service was later replaced by Google Cloud Messaging (GCM). This article covers what Google Cloud Messaging is, its features, and how it differs from FCM. Let’s have a detailed look at our blog –

What is GCM?

Google Cloud Messaging (GCM) was a service from Google designed for mobile notifications. It allowed developers of third-party apps to send information or data from their servers to applications meant for the Google Android Operating System and applications or add-ons created for the Google Chrome browser. This service was provided to developers without any cost. However, GCM was replaced by Google’s Firebase Cloud Messaging (FCM) in 2019.

Suggested Reading – Alternatives To Firebase Cloud Push Notifications (FCM)

How Does GCM Work?

Google Cloud Messaging (GCM), now known as Firebase Cloud Messaging (FCM), operates on a simple principle: a relay between a server and a mobile device. Here’s how it typically works – 

  • Server Setup: Developers integrate GCM into their server-side logic. They generate an API key to authenticate their server when sending messages.
  • Device Registration: When a customer installs an application that utilizes GCM, the app registers the device with Google’s servers. This registration generates a unique device token.
  • Message Routing: When the server wants to send a message to the app on a specific device or a group of devices, it sends the message along with the device token(s) to Google’s GCM servers.
  • Delivery to Devices: GCM uses the device token(s) to identify the target device(s). It delivers the message to the appropriate devices via a persistent connection (if available) or push notifications.
  • Displaying the Notification: The mobile device receives the message and alerts the customer if the app is closed or in the background. If the app is open, it can handle the message internally without showing a notification.
  • Customer Interaction: customers can interact with the notification to open the app or perform actions specified by the developer.

GCM handles various aspects of message delivery, such as queuing messages when devices are offline and optimizing message delivery based on the target platform and network conditions. This enables efficient and reliable communication between servers and mobile devices.

Here is the sample implementation path for GCM – 

  1. Create Project: Set up a new project in the Google Developer Console.
  2. Enable GCM API: Enable Google Cloud Messaging or Firebase Cloud Messaging API for your project.
  3. Configuration: Obtain an API key and Sender ID for server-client communication.
  4. Client-Side integration: Integrate GCM/FCM libraries into your app, request necessary permissions, and register devices to obtain unique tokens.
  5. Server-Side integration: Use the API key to send messages from your server to GCM/FCM servers.
  6. Testing and Troubleshooting: Test message delivery, monitor for issues, and handle success/failure callbacks.
  7. Maintenance: Stay updated with service changes and guidelines for ongoing efficiency.

Specific steps might vary based on your platform and service (GCM or FCM). Always refer to platform-specific documentation for precise implementation guidance.

Features of GCM

Google Cloud Messaging (GCM) facilitated mobile communication by offering reliable and scalable messaging services. It supported cross-platform messaging for Android and Chrome applications, allowing developers to send notifications and data to targeted devices. Let’s look at some of the key features of GCM – 

  • Cross-platform Messaging: Supports messaging across various platforms, including Android, iOS, and web applications.
  • Notification Support: Enables developers to send notifications to customers as basic text alerts or more detailed notifications with images and action buttons.
  • Delivery Reports: Provides delivery reports and analytics to track message status and customer interactions with notifications.
  • Synchronized Notifications: Enables synchronized notifications across multiple devices belonging to the same customer.
  • Security: Offers secure communication between the app server and client devices, ensuring data integrity and confidentiality by using authentication keys.
  • Free of Charge: Provided to developers at no cost, making it accessible for app development and implementation.
  • Integration with Firebase: Seamlessly integrates with other Firebase services, enhancing app development, analytics, and customer engagement.

These features collectively make GCM/FCM a robust and versatile solution for developers to handle messaging, notifications, and customer engagement within their applications. They also make the bedrock for the various benefits that GCM provides:

Benefits of Using GCM 

Here’s a distinct breakdown of the benefits of using Google Cloud Messaging (GCM)/Firebase Cloud Messaging (FCM) separate from the earlier features:

  • Instantaneous Communication: Ensures real-time delivery of messages, facilitating immediate interaction between the app and customers.
  • Consistent Reliability: Maintains a high level of reliability across different network conditions, ensuring messages reach their intended recipients consistently.
  • Scalability Without Hassle: Scales effortlessly to accommodate the app’s growth, handling messaging needs even as the customer base expands.
  • Engaging Notifications: Supports rich and interactive notifications, allowing developers to create engaging and visually appealing customer messages.
  • Precision Targeting: Provides precise targeting options for messages, allowing developers to tailor communication to specific customer segments or devices for enhanced engagement.
  • Insightful Analytics: Offers robust analytics and reporting tools, enabling developers to gain insights into message delivery and customer interactions, facilitating data-driven optimizations.
  • Cost Efficiency: Provides a cost-effective solution by being available to developers at no charge, making it accessible for implementing messaging functionalities in apps without added expenses.


Firebase Cloud Messaging (FCM) emerged as an evolution of Google Cloud Messaging (GCM), offering a more comprehensive platform within the Firebase suite. FCM retains the core functionality of GCM but comes with additional features and integration possibilities. 

Unlike GCM, FCM is part of the broader Firebase ecosystem, providing developers access to comprehensive tools beyond messaging. FCM supports multiple platforms, including Android, iOS, and web applications, allowing developers to implement unified messaging across various devices seamlessly.

One of the significant enhancements in FCM is its support for rich notifications. FCM allows developers to create and send notifications with images, action buttons, and customized layouts, enhancing customer engagement and interaction. In contrast, GCM primarily provided basic notification capabilities without the richness and interactivity that FCM offers.

Let’s compare the different features of GCM vs FCM in this table –

AspectFirebase Cloud Messaging (FCM)Google Cloud Messaging (GCM)
PlatformPart of Firebase suite; supports Android, iOS, and webSupported Android platform, evolved into Firebase
IntegrationIntegrated with Firebase platform for a broader set of toolsIntegrated with the Firebase platform for a broader set of tools
Notification SupportSupports rich notifications with images, buttons, etc.Basic notifications without rich features
AnalyticsEnhanced analytics and reporting tools within FirebaseLimited analytics; mainly message delivery confirmation
SecurityOffers secure transmission with encryption and authenticationSimilar security measures for data transmission
Ease of UseSimplified and integrated setup within the Firebase platform. Standalone setup and configuration for GCM
Development ToolsAccess to a wider array of Firebase development toolsLimited to GCM-specific functionalities
Continued SupportContinual updates and support as part of Firebase servicesLimited ongoing development since transition to FCM
Cross-Platform SupportWidely supports multiple platforms seamlesslyPrimarily focused on Android platform
Cost StructureFree to use, part of Firebase suite with paid tiers for advanced featuresInitially free; transitioned into Firebase, retains free usage

GCM vs Push Amplification™

When stacked up against GCM (now known as FCM), Push Amplification™ can give over 200% more audience reachability. Here’s a detailed comparison.