Comprehensive Overview of Server Sent Events vs Websocket

Overview Comparison Table

Here's an easy-to-understand comparison table, highlighting key similarities and differences between Server-Sent Events (SSE) and WebSocket.:

AttributeServer-Sent EventsWebSocket
Data DirectionUnidirectional (Server to Client)Bi-directional (Server and Client)
ConnectionSingle HTTP connectionSingle TCP connection
ProtocolHTTPWS / WSS
Real time CapabilityYesYes
Data FormatTextEither Text or Binary
HeadersWith every messageOnly at handshake

The main difference between Server-Sent Events (SSE) and WebSocket is that SSE is unidirectional (allows communication from server to client), only supports text data, and keeps connection alive for automatic reconnection, while WebSocket is bidirectional (allows communication from client to server and vice versa), supports both text and binary data, but does not have built-in support for reconnection.

What are Server Sent Events

Definition and Overview of Server Sent Events

Server Sent Events (SSE) is an advanced technology, part of the client-server communications model, that offers real-time updates and true streaming. With SSE, server push functionalities are executed via a single HTTP connection. This one-way communication champion transmits text-based event data from server to client. A built-in reconnection support handles disconnection scenarios and automatic reconnection.

Server-Sent Events 2 specification promise, which was designed to tackle the previous six-connection limit per domain, improved the connection robustness and allowed for better real-time communication landscape. As preference in the real-time applications industry shifts away from the rest model, Server-Sent Events emerged as an effective alternative. In terms of performance, it efficiently supports real-time interactions, status updates, and promotes more responsive experiences.

Most modern browsers natively support Server Sent Events. And through the EventSource API, the initial request is established, creating a persistent connection between the client and server. However, unlike WebSocket, Server Sent Events only support a uni-directional data stream (server to client), which leads to some of its limitations and, by extension, makes WebSocket an attractive alternative in certain situations.

Examples of Server Sent Events

  1. Real-Time News Feeds: News applications leverage Server-Sent Events to push updates to browsers. The server sends the newly available contents to the client, eliminating the need for users to refresh their browser tabs.

  2. Real-Time Chart: In a financial trading application, real-time server-initiated events update a chart that displays stock prices. Thus, traders can get real-time information to make informed decisions.

  3. Collaborative Tools: Some tools, like collaborative editors, take advantage of Server Sent Events to broadcast changes made by one user to other users. SSE's real-time capabilities make this synchronization faster and more efficient.

What is WebSocket

Definition and Overview of WebSocket

WebSocket is an advanced technology that provides bi-directional, full-duplex communication channels over a single TCP connection. In simpler terms, this means that WebSocket allow for two-way communication. It's a persistent connection, meaning that once the connection is established, it stays open until the client or server decides to close it. This is a key benefit in real-time applications where you need continuous data exchange.

With WebSocket, the server can send data to the client without being prompted. It overcomes the limitations of traditional HTTP communications where client must initiate requests. One major benefit of this protocol is that headers are only sent at the initial handshake, saving valuable bytes of data during data transmission, reducing latency, and improving efficiency.

WebSocket are widely recognized for their performance benefits in modern web development, particularly in real-time applications. However, they must be used judiciously as they can add complexity and unnecessary overhead when simpler, request-response communication will do.

Examples of WebSocket

  1. Live Streaming: WebSocket is great for live streaming. It's near-universal support and built-in WebSocket support in most modern browsers makes it a solid choice for applications that need high speed, real-time data updates like audio and video streaming applications.

  2. Chat Applications: WebSocket are also perfect for chat applications where instant communication is crucial. With WebSocket’s two-way channel, messages can be sent and received at the same time between multiple users.

  3. Online Gaming: WebSocket are a popular choice for online gaming. In multiplayer games, for example, players' data, scores, and positions are constantly updated. Using WebSocket gives a great experience since it’s all done in real-time.

  4. Collaborative Editing Tools: In applications where multiple users can edit the same document simultaneously, WebSocket provide the real-time updates and communication needed for smooth user experiences. Examples include Google Docs and other online collaborative platforms.

This was just a quick introduction about WebSocket and its uses. Understanding when to use WebSocket and when to use alternative technologies (like Server Sent Events) can be a key factor in creating a great user experiencing while maintaining efficient, performant applications.

Server Sent Events vs WebSocket: An In-Depth Comparison

The Unique Features of WebSocket and Server-Sent Events

WebSocket enable real-time capabilities in applications such as live streaming, chat applications, and online games. They provide a persistent, bi-directional connection where the client and server can communicate freely.

Server-Sent Events (SSE) on the other hand, offer real-time updates using a single HTTP connection, ideal for broadcasting frequent updates from server to client, like real-time news feeds, stock updates, and more.

Dissimilarities and Similarities

Both technologies are designed for real-time communications but differ in significant ways. WebSocket provide full-duplex communication, allowing data to flow in both directions simultaneously. This is perfect for chat apps or multiplayer games where server and client need to exchange data at the same time.

On the flip side, Server-Sent Events are unidirectional, meaning that data can only flow from the server to the client. This kind of one-way communication is amazing for applications where you need real-time updates, like news apps or stock price feeds.

Data Transmission Format

Another key difference between these two is their data transmission format. Server-Sent Events can only send text-based event data, encoding all of its messages as strings.

WebSocket, however, have the ability to send either text or binary data. This gives WebSocket a leg up for use cases where binary data is being sent, like images or video.

Evaluating the Benefits and Downsides of Each Real-Time Technology

Pros and Cons of Server Sent Events


  • Simplicity: Server Sent Events are simple to understand and implement as they use regular HTTP protocol.
  • Automatic Reconnection: In case of lost connection, SSE will auto-reconnect which is a helpful feature.
  • Designed for updates: It's ideal for server to client updates as the technology was designed for such usage.


  • Unidirectional: Server-Sent Events only allow for one-way communication (from server to client). This could be a limitation when you want two-way communication.
  • Data type: SSE can only send text data. If you need to send binary data - you're out of luck.

Pros and Cons of WebSocket


  • Full Duplex: WebSocket allows two-way communication which is useful for real-time, interactive applications.
  • Allows for binary data: WebSocket are not limited to text-based data – it can also send binary data.


  • Complexity: WebSocket are more complex to implement and require more server resources.
  • Lack of automatic reconnection: Unlike SSE, WebSocket do not have built-in support for reconnection. If the connection closes, you'll have to handle reconnections manually.

When to use Server Sent Events

If you need a real-time connection where the primary data flow is from server to client, think about using Server-Sent Events. SSE is perfect for a use-case when the server needs to push real-time updates to the client but doesn't need anything back. For instance, live news updates or stock price updates.

Examples of scenarios where Server Sent Events are suitable

  1. Real-Time News App: For a digital newspaper application that pushes the latest news to the client in real-time, Server Sent Events would be an appropriate choice.
  2. Stock Market App: In a stock market app that shows real-time fluctuations of stock prices, SSE would fit nicely due to its push nature and automatic reconnections.

When to use WebSocket

If your application requires real-time two-way communication between the server and client, WebSocket is the right technology. If you need fast, efficient bi-directional communication, like chat apps or online multiplayer games, WebSocket takes the cake.

Examples of scenarios where WebSocket are suitable

  1. Chat Applications: For instance, in a chat application where users need to send messages to a server and receive responses in real-time, WebSocket would be the ideal pick.
  2. Multiplayer Online Game: In an online game where player positions need to be simultaneously updated and broadcasted to every connected client, WebSocket prevails due to its fast, full-duplex communication.

Examining Real-World Use Cases for SSE and WebSocket

To reflect on real-world use cases, Twitter's real-time feed implementation is a good example of Server-Sent Events, as it allows Twitter to push real-time updates to the browser.

Considering WebSocket, many real-time multiplayer browser games use it to get real-time bidirectional communication. '' is one such popular game which uses WebSocket for fast updates and to maintain the game's high performance.

Performance and Scalability Considerations

Fewer Connections with High Throughput Per Connection

Fewer connections with higher throughput per connection, like with WebSocket, can lead to more efficient use of server resources due to lower overhead. With WebSocket, the initial handshake may be heavier due to the more complex WebSocket protocol. But, it's a one-time cost. After that, the data transfer between the client and the server requires minimal overhead which reduces latency and increases speed.

This aspect makes WebSocket ideal for situations where we have fewer but very active clients, like a multiplayer online game or real-time auction site.

Many Connections with Lower Throughput Per Connection

In contrast, having many connections with lower throughput per connection as in Server Sent Events (where only the server can send messages) could theoretically take more server resources due to the higher overhead from more open connections. But, since Server-Sent Events only involves sending updates from server to clients, the server has a lighter load to deal with.

This makes Server-Sent Events perfect for applications with hundreds or even thousands of clients that just need to receive updates and don't send much data back, like a weather update application or a social media news feed.

Assessing the Potential Drawbacks and Extensibility of Both Technologies

While WebSocket come with the advantage of two-way communication and faster data transfer with lower latency, it could become resource-intensive if not managed properly. Inefficient use often leads to server overloading, making its scalability a potential drawback.

On the other hand, Server-Sent Events are much simpler and lighter as the server just has to push updates. But, it can only send text data and is unidirectional. Besides, due to the limited capabilities of SSE, it's less extensible; for complex and interactive applications, WebSocket should be preferred.

In summary, both technologies have their potential drawbacks and scalability issues, but these issues can be mitigated by using the right type of technology based on the type of application and requirements. It all boils down to the unique demands of your project.

Exploring Browser Support Across Different Technologies

WebSocket Browser Support

WebSocket have an impressive level of support across all modern browsers. This includes the latest versions of Google Chrome, Mozilla Firefox, Safari, and many others. Even mobile browsers have widespread support for WebSocket. This compatibility makes it a viable choice for an array of web applications and websites. WebSocket may run into issues, however, with older browsers and some corporate firewalls.

Even if your application needs to support older browsers, don't worry! Libraries like Socket.IO can provide fallback options to maintain real-time connections even in less-than-ideal conditions.

Server-Sent Events Browser Support

Server-Sent Events also boast wide-ranging support across most modern browsers including Chrome, Firefox, and Safari. But, browser support can be a bit of an issue when dealing with Internet Explorer (which does not support SSE) or Microsoft's Edge.

If Internet Explorer compatibility is necessary, then third-party libraries can be used to add Server-Sent Event support, or perhaps consider alternatives like Long Polling or WebSocket.

Both WebSocket and Server-Sent Events are widely supported across multiple browsers and platforms. However, it's always essential to keep your target audience's browser usage in mind when creating your web application.

Practical Applications: Getting Started with These Technologies

Kick-starting Your Journey with WebSocket

Working with WebSocket starts with creating a WebSocket connection. Here is an example code snippet in JavaScript:

//creating WebSocket connection var connection = new WebSocket("ws://"); //connection is open connection.onopen = function () { connection.send("Hi Server!"); //send a message to the server };

In this code, we create a new WebSocket object and pass the URL of the server. Once the connection is open, we send a greeting message to the server.

However, this is a simplified introduction, and WebSocket have various other methods and properties to handle communication efficiently.

Basic Guide to Starting with Server-Sent Events

To start with Server-Sent Events (SSE), you would use the EventSource API. Here is an example using JavaScript:

//create an object var source = new EventSource("api/news"); //an event handler for message event source.onmessage = function (event) { document.getElementById("result").innerHTML += + "<br>"; };

In the above code, we create a new EventSource object and pass the URL of the data source. Then we use the onmessage event handler to listen for messages from the server and update the HTML page with the message data.

As with WebSocket, this basic code only scratches the surface of what you can do with Server-Sent Events, but it serves as a starting point on your journey to master real-time communication technologies in web development.

Key Takeaways

Recap of the Main Features of WebSocket and Server-Sent Events

WebSocket offers a robust real-time, full-duplex communication protocol over single TCP connection. It supports binary data and can send data in both directions, making it ideal for applications that need simultaneous two-way interaction, like a chat application or a multiplayer game.

Server-Sent Events (SSE), on the other hand, is a technology that provides real-time updates from the server over a single HTTP connection. Its ability to auto-reconnect makes it great for applications that need to push updates from the server to the client.

Reinforcing the Differences and Similarities

WebSocket and Server-Sent events might seem very similar at first, as both provide real-time data communication. However, they have significant differences. WebSocket provide bi-directional communication whereas SSE is more suitable for unidirectional communication (server to client).

Another major point of difference is that WebSocket allow both text and binary data, while Server-Sent Events only support text.

Final Verdict: Server-Sent Events vs WebSocket - Which Is Better?

The answer to this highly depends on what you need for your application. If you need two-way communication, WebSocket is your best bet. If you only need updates from your server to the client, Server-Sent Events would be a great choice. However, it's important to remember that these technologies can also be used in combination to leverage the benefits of both.

In the end, there isn't a 'best' option — only the 'right' option that fits the needs of your application. After all, successful software engineering is about using the right tool for the job!

FAQs about Server Sent Events and WebSocket

How Do Server-Sent Events Impact the Performance and Scalability of My Application?

While Server-Sent Events offer a simple and efficient way to push real-time updates from server to clients, they do consume server resources if not managed properly and can impact performance and scalability. Efficient handling of SSE connections can mitigate this and should be an integral part of your application's design and architecture for large-scale usage.

What Future Development Trends Can Affect WebSocket and Server-Sent Events Technology?

Upcoming technologies like HTTP/3 and WebTransport may change the landscape of real-time communications. HTTP/3's improved methods could enhance Server Sent Events performance, and WebTransport might merge the benefits of both WebSocket and Server-Sent Events.

Another trend to watch for is the increasing use of WebSocket and SSE in Internet of Things (IoT) devices for real-time data exchange, which may lead to new libraries and more support for these technologies.

Keep in mind, the future of web development is ever-evolving, and staying updated with the latest trends is essential for making informed technological decisions for your project.