This article compares Firebase and Socket.IO, two solutions that are frequently used to power realtime features and experiences like chat and multiplayer collaboration. We’ll go through the following points:
What is Firebase?
Firebase is a Backend as a Service (BaaS) platform that helps you build, test, release, and monitor web and mobile apps for end-users. Firebase provides numerous features out of the box, such as:
Realtime database. At its core, Firebase is a cloud service that allows you to store data related to your application and service. Firebase offers two different non-relational database options: the Firebase Realtime Database, and Cloud Firestore, the newer database for mobile app development, providing a more intuitive data model and enhanced capabilities for querying data.
Cloud and in-app messaging. Both Firebase Realtime Database and Cloud Firestore can push realtime updates to client devices following any changes to the database. There’s also Firebase Cloud Messaging, a service that allows you to send native push notifications and notification messages across platforms (iOS, Android, web).
Hosting. Firebase provides secure hosting on Google Cloud.
Integrations. Given that Firebase is powered by Google, this naturally extends its functionality via integrations with services such as Google Pub/Sub, Google Cloud Functions, and Google Analytics.
App analytics. Firebase comes with a dashboard for visualizing your app’s activity, so you can make critical business decisions based on this data.
Firebase pros and cons
We’ll now cover some of Firebase’s key advantages and disadvantages.
Firebase helps app developers move quickly: you don’t have to worry about hosting, provisioning, and managing backend processes and components like databases, data storage, and authentication. Firebase’s collection of services makes the entire development cycle shorter and more straightforward.
Firebase has good technical documentation, and detailed SDK and API reference, making it easy to get started and use the platform. Going beyond docs, there are about 1.5 million apps built with Firebase, so there’s a pretty big community of experts who can help you with questions and issues.
Most of the Firebase services are free to start with, which is great if you are new to Firebase and simply want to test the platform, to assess if it’s the right choice for your project.
An instance of the Firebase Realtime Database has a limit of 200.000 concurrent connections and 1.000 write operations per second. To scale beyond these limits, you have to use sharding, which is a notoriously difficult process.
Vendor lock-in is an issue when you use Firebase. For example, if one day you conclude that the Realtime Database / Cloud Firestore is unsuitable for your use case, it’s hard to migrate to another (NoSQL) database. This is because of the way data is stored - a JSON tree in the case of the Realtime Database, respectively collections of documents (which are very similar to JSON data) in the case of Cloud Firestore.
There are plenty of horror stories of costs escalating out of control, especially if you are new to Firebase, and don’t yet have a good grasp on the pricing model and how to engineer your apps in a cost-effective manner. See How not to get a $30k bill from Firebase and We burnt $72K testing Firebase + Cloud Run and almost went bankrupt for details.
What is Socket.IO?
Socket.IO is an open-source realtime library that enables low-latency, bi-directional communication between web clients and servers. Built on top of the WebSocket protocol, Socket.IO provides additional capabilities compared to raw WebSockets:
Fallback to HTTP long polling for environments where WebSockets aren’t supported (e.g., older browsers and some corporate networks with proxy servers).
Disconnection detection, packet buffering, and automatic reconnections.
Broadcasting to all clients, or a subset of clients via rooms.
Acknowledgments (via callbacks).
Socket.IO advantages and disadvantages
Making use of namespaces enables you to minimize the number of TCP connections used, and save socket ports on the server, while broadcasting allows you to efficiently distribute data in scenarios where you need to fan out the same message to multiple users.
Socket.IO is easy to get started with; it provides a simple API for both the client side and the server side, making it straightforward to implement realtime functionality into your application.
Integrations with various solutions for horizontal scaling: Redis, MongoDB, Postgres, AMQP / RabbitMQ, so you can choose the one that best suits your needs. Note that you must use one of these when you scale beyond a single Socket.IO server, to pass events between nodes, and ensure that events are properly routed to all clients.
Socket.IO does not guarantee exactly-once messaging semantics. By default, Socket.IO provides an at-most-once delivery guarantee. This means there’s a chance some messages might never get delivered to recipients, especially when poor network conditions and disconnections are involved. If you’re unhappy with the default semantics, you can configure Socket.IO to provide an at-least-once messaging guarantee. However, this brings additional engineering complexity - you have to use acknowledgments, timeouts, assign a unique ID to each event, persist events in a database, and resend events upon reconnections.
Socket.IO is designed to work in a single region, rather than a multi-region architecture. This can lead to issues such as increased latency (if your users are in different regions), and even system downtime - what happens if the datacenter where you have your Socket.IO servers goes through an outage?
Comparing Firebase and Socket.IO
In this section, we’ll look at the conceptual differences between Firebase and Socket.IO, and compare their feature and capabilities. We’ll also cover Firebase and Socket.IO use cases, including scenarios when you can use Firebase and Socket.IO together.
Key conceptual differences between Firebase and Socket.IO
There are some key distinctions between Firebase and Socket.IO:
Socket.IO is a free-to-use, open-source solution, while Firebase is a commercial (paid) solution.
You have to host Socket.IO yourself (or find someone to do it for you). In contrast, Firebase is a managed, cloud-based offering.
Socket.IO is a rather simple realtime library, designed to handle realtime communication (primarily over WebSockets), and nothing else. Meanwhile, Firebase is a more complex solution that allows you to build a complete app, with realtime messaging over WebSockets, push notifications, hosting, database storage, authentication, etc.
Firebase can work in a multi-region setup (if you use Cloud Firestore). In comparison, Socket.IO is designed to work in a single region, rather than a multi-region architecture.
Socket.IO doesn’t provide a mechanism to generate and renew tokens. Firebase, on the other hand, offers an authentication service.
Firebase vs Socket.IO: features and capabilities
The table below compares Firebase and Socket.IO features and capabilities:
Type of solution
Firebase offers two pricing plans: the Spark plan (free) and the Blaze plan (pay as you go), which is recommended for building apps at scale.
Free to use (open source)
Managed for you
You have to manage it yourself
The Firebase Realtime Database has a limit of 200.000 concurrent WebSocket connections. You can scale beyond this limit by sharding your data across multiple instances.
Cloud Firestore can autoscale up to 1 million concurrent connections.
Unclear to what extent you can scale Socket.IO.
99.95% for hosting and the Realtime Database.
99.999% if you are using Cloud Firestore in a multi-region configuration.
Is it multi-region?
Cloud Firestore is available in multi-regional configurations (but the Realtime Database is only a regional service).
Socket.IO is designed to work in a single region.
Guaranteed message ordering
Guaranteed message delivery (exactly-once)
Native push notifications
Limited number of integrations, primarily with Google Cloud services, such as Google Pub/Sub and Google Analytics.
Only provides a few integrations with tools like Redis, MongoDB, and Postgres. You need to use one of them if you plan to scale to more than 1 Socket.IO server.
Cloud Functions for Firebase. No support for other serverless platforms, such as AWS Lambda or Azure Functions.
Firebase provides two different NoSQL databases: the Firebase Realtime Database, and the more recent Cloud Firestore.
HTTP long polling
Pub/sub messaging / broadcast
Yes (but only for the Realtime Database; this feature is not supported for Cloud Firestore)
Good security, including an authentication service, permissions, and compliance with standards such as SOC 2 and EU GDPR.
Basic native security capabilities. For example, it doesn’t provide a mechanism to generate and renew tokens.
Socket.IO provides a minimalistic Admin UI.
Firebase and Socket.IO use cases
Both Firebase and Socket.IO can be used to deliver realtime features and apps like live chat and multiplayer collaboration. However, Firebase and Socket.IO play different roles in your tech stack and system architecture. Sometimes, you can even use Firebase and Socket.IO together.
When to use Firebase?
You can use Firebase if:
You’re looking for an all-in-one app development solution that includes diverse features like data storage, hosting, realtime messaging, and authentication.
You're building a mobile or web app that requires realtime data synchronization. Firebase provides two different NoSQL databases: the Firebase Realtime Database, and the more recent Cloud Firestore. Data stored can be synchronized across all clients in realtime, with low latencies - every time there is a change in the DB, connected devices will receive an update. Note that Firebase uses WebSockets for data synchronization with clients.
You want to send native push notifications to client apps (note that in comparison, Socket.IO does not provide native push notification capabilities).
When to use Socket.IO?
Socket.IO is useful if:
You are looking specifically for a WebSocket-based library to power bidirectional, event-based realtime communication for your app.
You’re working with WebRTC, and you need a signaling mechanism to coordinate communication between peers. WebSockets (and implicitly, Socket.IO) are frequently used to enable signaling for WebRTC apps.
You need more control over realtime communication. Socket.IO can be connected to different backend / DB options, and allows you to flexibly tailor realtime communication to your use case. In contrast, Firebase is more restrictive, offers only two database options, and comes with a pre-designed communication model (it forces you to store all events you want to push to connected clients in the Firebase database).
When to use Firebase and Socket.IO together?
There are scenarios where you can use Socket.IO and Firebase in complementarity. That’s because Socket.IO is a more flexible (and arguably better) choice for realtime, bidirectional communication, while Firebase provides other features that come in handy when building web apps.
Let’s assume you want to build a digital whiteboard app with multiplayer collaboration features. You could authenticate users and manage permissions with Firebase Authentication, store user-generated content in Firebase Cloud Storage, and run backend code in response to various events (e.g., a new user connecting) with the help of Cloud Functions for Firebase. Alongside these Firebase capabilities, you could use Socket.IO to handle realtime communication between connected clients, for features like live cursors.
Another example - say you’re building a chat experience and using Socket.IO as your realtime communication solution. But if you want chat users to receive push notifications when they’re not actively using the app, Socket.IO can’t help, as it relies on a persistent socket connection. You could, however, complement Socket.IO with Firebase Cloud Messaging, a service that allows you to send native push notifications to client devices.
Socket.IO and Firebase alternatives
We hope this article is a good starting point for you to discover the advantages, disadvantages, and differences between Firebase and Socket.IO. There are many other alternative solutions you can use instead of Firebase and Socket.IO to engineer realtime features and web apps. We encourage you to explore these alternatives to see if there are any better fits for your specific use case:
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