WebSockets vs. HTTP: What to use for your project
When selecting a communication protocol for your project, it is crucial to consider the need for fast and reliable data exchange. This is particularly important with the rapid increase in IoT development, which generates enormous amounts of data that require real-time transmissions.
The two most common communication protocols are WebSockets and HTTP, each with distinct advantages and specific uses. This article explores the comparison of WebSockets vs. HTTP, provides common use case, and explains when to use each protocol, helping you choose the best one for your project.
What is WebSocket?
WebSocket is a stateful communication protocol that provides a persistent full-duplex channel between the server and the client. It achieves this by reusing the same Transmission Control Protocol (TCP) connection that was opened at the beginning of the communication (during the opening handshake).

Before exploring the concepts of WebSockets in detail, it’s important to first examine the well-known HTTP protocol. Understanding the differences between HTTP and WebSockets will clarify why you can’t rely on just HTTP for all communication needs.
What is HTTP?
HTTP (Hypertext Transfer Protocol) is a widely used web communication protocol. However, depending on the specific use case, it may not always be the best choice. HTTP was designed as a stateless connection-oriented protocol for data retrieval on request. This implies that it opens a new, one-time connection for every request and terminates after responding to a request.
Moreover, HTTP is a one-sided connection. A client sends requests to the server, and the server responds to them. This connection is called an upstream connection or a client polling of the server (from the client to the server). On the contrary, the server cannot initiate a connection with a client (downstream connection). This is because it does not keep track of its clients.
Consider a case where data is updated thousands of times per second on the server’s side. If you want to propagate these data updates to the client using HTTP, you will encounter specific issues. Setting up a very frequent (thousand times per second) polling of the server for every client would be necessary. This activity would result in thousands of HTTP connections for every client opening and closing every second, putting considerable load both on the clients and the server.
Furthermore, it is doubtful whether all clients will receive all data updates as frequently as they come to the server. This is because the time it takes to create an HTTP connection may be longer than the interval between the updates in the data on the server. Let’s not forget the increased computational load on the server, which can cause delays in response. The server now needs to handle thousands of requests from many clients during short time intervals.
This is where the WebSocket protocol (or simply “WebSockets”) comes into play.
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How does the WebSockets protocol work?
The philosophy behind WebSockets is simple: use a single connection for all communication with a client. Instead of opening and closing the connection on every request, establish it first and reuse it whenever you want to send new data. This bidirectional (two-way) connection is crucial. It can facilitate both upstream (client to server) and downstream (server to client) messaging, unlike traditional HTTP connections.
However, this also means the connection now needs to be stateful, and the server must keep track of all the established connections to every end-user/client. This ensures the server knows where to send the data to reach a specific client. The main benefit is that there is no connection-establishment overhead at every client’s request. The server can now push data downstream to the clients, unlike HTTP, which only supports upstream connections. This is exactly what you need to solve the previous use case with a thousand data updates per second.
While WebSockets provide a secure and reliable connection over TCP, it’s important to note its limitations. WebSockets successfully handles cases like network packet loss, incorrect packet order, or packet corruption. However, it does not handle issues like timeouts or loss of connectivity to the communication party due to network problems. The application developer must explicitly handle these application-level issues to prevent data loss. Despite these limitations, continuous communication with WebSockets is faster than with HTTP.
A WebSocket connection only terminates whenever one of the communicating parties decides to terminate it or becomes unavailable/leaves the conversation. In the case of HTTP, the connection always terminates after the server’s response.
To establish a WebSocket connection, the browser issues an Upgrade HTTP request to the server, indicating the need to establish a WebSocket channel.
Note: Establishing a WebSocket connection requires issuing one HTTP Upgrade request.
WebSockets vs. HTTP summary
The following table is a short comparison of WebSocket vs. HTTP protocols:
WebSocket | HTTP |
Works on application layer in the OSI model | Works on application layer in the OSI model |
Stateful | Stateless |
Works over TCP connection | Works over TCP connection |
Establishes a single persistent connection | Establishes a new connection for every request |
Terminates connection only when one of the communicating parties terminates it | Terminates connection right after sending a response to the request |
Bidirectional connection (both upstream and downstream) | Unidirectional connection (only upstream possible) |
Does not define any format for data that is being exchanged | Uses HTTP format with appropriate headers, for every HTTP request type |
Initial request to establish WebSocket is sent as an HTTP Upgrade request | No initial request needed, works as a request-response model with a one-time connection |
If you want to explore more protocols, check out this blog post to see how HTTP compares to MQTT.
When to use WebSockets?
As you have seen in the sections above, WebSockets are a fitting solution whenever you need to update data (from the server) frequently on the client or exchange messages between a client and server in both directions.
You can think of the frequently changing data as real-time data. Imagine a meteorological station that takes numerous measurements per second in various real-world locations and sends this data to the server. While this example does not represent how these stations operate, a data visualization application for such a station would be an excellent use case for WebSockets.
In short, the WebSocket protocol is a good solution for interactive, dynamically updated services and real-time web applications. However, there is no need to use it for data that doesn’t require frequent updates, or updates rarely and does not need immediate pushing to the client. For example, online catalogs, articles, and this blog you are reading do not update in real time. Therefore, using WebSocket for these cases won’t speed up the connection (since establishing a WebSocket channel requires issuing an HTTP request first anyway).
Some well-known real-world examples of WebSocket applications include:
- Browser push notifications only use HTTP or WebSocket. You would need to establish a WebSocket connection to connect downstream and push messages to the client from the server. For example, you can display notifications about incoming messages in a personal cabinet of a ticketing system or an online store.
- Online chats / real-time comment sections, including customer support services, hold the same rationale as above. Note that you are also dealing with systems that are liable to frequent updates: new messages/comments and so on.
- In online games, specifically in multiplayer, the user receives data about new actions and state changes of the other players on the map. Then, the client part of the game renders the changes.
- Exchanges, trading platforms, and other commercial services with rapidly changing statistics, prices, etc. Such services deal with dashboards and graphs with real-time data, which is a direct use case for the WebSocket protocol.
- Social networks and blogs like Facebook Messenger, Instagram, or Telegram use WebSocket for sending, receiving, and updating messages (especially in the browser, since mobile devices implement different protocols).
When to use HTTP?
While the WebSocket protocol is ideal for real-time, interactive data exchanges, HTTP remains the preferred choice for many scenarios:
- Static content: Use HTTP to transmit static information including, online catalogs, articles, and blog posts where there is no need for constant information updates and real-time communication.
- Form submissions: Perfect for submitting web forms like contact forms, registration forms, and online surveys.
- Standard API requests: Use HTTP for RESTful APIs in cases where API requests are made periodically and do not need frequent updates.
- File downloads: HTTP is a good choice for downloading files such as PDFs, images, and other media files, which can be downloaded in a single request-response cycle.
- Non-interactive applications: For applications that don’t need real-time updates or frequent user interactions, like documentation or informational sites.
Real-world examples of HTTP include:
- Static websites: Sites with limited interactivity, for instance, corporate sites, portfolios, and individual weblogs.
- E-commerce platforms: Online stores where information about products and specifications is not updated in real-time.
- News websites: News articles that update periodically but don’t require continuous updates to the client.
- Content management systems: Platforms like WordPress, where individual user actions handle content updates rather than continuous server push.
HTTP is a robust protocol suitable for traditional web applications where real-time updates are not critical. It ensures simplicity and efficiency in delivering web content.
Websockets and HTTP in the IoT realm
Now that you understand the comparison of WebSockets vs. HTTP, let’s explore how they integrate into the IoT world. Typically, MQTT is commonly used in IoT. However, HTTP and Websockets also have their own applications. These protocols often integrate MQTT brokers with other systems, thereby bridging the gap across different pieces of an IoT infrastructure. For more information about MQTT, check out this comprehensive MQTT Protocol Guide.
Common uses of the HTTP protocol include:
- Pushing data from IoT devices to server-side applications for further processing.
- Retrieving configuration or firmware updates from a central server.
- Interfacing IoT devices with traditional web APIs to extend functionality.
On the other hand, the WebSocket protocol is ideal for:
- Sharing MQTT data with client-side applications running in the browser, such as statistics dashboards or interactive real-time management panels. If you want to explore how to configure MQTT over WebSockets further, check out this article.
Wrap-up
It is important to consider the characteristics of your data and communication needs, when selecting the best communication protocol for your project. WebSockets offer a persistent and full-duplex connection, making it suitable for real-time applications like chat applications, multiplayer games, and trading platforms that require constant updates and minimal delays. In contrast, HTTP is more appropriate for static content, standard API requests, and cases where frequent updates are unnecessary. Understanding these differences will enable you to choose a suitable protocol for your specific requirements and enhance performance and user experience.
Enroll in our free courses at the MQTT Academy to learn more about other protocols such as MQTT.
About the author
Tizian is a dedicated team member of Cedalo and has embraced the opportunity to wear many hats, driven by an unwavering passion for technology. His journey has been dynamic, allowing him to craft a multifaceted expertise.
His foundation in IT, developed during his studies, has been further refined through hands-on experience in various roles.
As a Quality Manager, Tizian ensures the functionality and usability of Cedalo's products. As a Solutions Engineer, he eagerly dives into technical inquiries, guiding their clients toward success. As a Scrum Master, he leads their agile team, fostering collaboration and effective communication.