It can be difficult to determine what protocol or development structure to use to manage your data needs — especially when you’re unfamiliar with your options. Two widely-used and well-known options are REST and WebSockets. It’s common for people to ask what the differences and similarities are between REST and WebSockets. So we’ll answer just that. In this article, we’ll compare WebSockets and REST, helping you make an informed decision on which to use for your next web application.

What Is REST?

REST is a stateless architectural style for building application programming interfaces (APIs). In other words, it’s a way to structure communication between different applications on the Internet using constraints and principles to ensure that these applications understand each other. Because REST is unidirectional, meaning the REST API will only give data when requested to share, you must ask for the proper resource to receive what you’re looking for. To illustrate how REST works, imagine you want to purchase a t-shirt from an e-commerce web store via their website. Because the web store follows modern web development practices, it loads the t-shirts by querying an API. As with most APIs, there’s a client, such as a browser, and a server. The client sends a request, and the server gives a response. In this case, your browser sends a request that asks about all available t-shirts. Since the site uses a REST API, this request will query a resource through a resource indicator. A resource indicator is just an HTTP link, such as this one: http://api.exampletshirtstore.com/shirts When you query the link, the server will return the description of the resource. Usually, it’s in a format called JSON, but REST doesn’t actually prescribe specific formats. It will look something like this:
{
"shirts": [{
"name": "Basic",
"color": "white"
},
{
"name": "Advanced",
"color": "blue"
},
{
"name": "Luxury",
"color": "black"
}
]
}
Of course, you won’t see anything like this on the web page (or in the HTML). The browser will render it for you in a more presentable manner. REST is appealing to developers for several reasons. First, it’s simple to use. It’s standardized while still allowing for a high degree of flexibility. REST is also a great way to decouple the client and the server. The client doesn’t need to know how the database is built. it just needs to know how to query a resource and render it.

What Is WebSocket?

WebSocket is a way to open a two-way communication channel with a server. It enables you to both send messages to the server and receive event-driven messages back. WebSocket is a wholly different protocol from HTTP, which is what REST APIs usually use. So, while you’re accessing REST resources with links that look like regular web links, a WebSocket would use ws:// or ws:///. Usually, a client would send a regular HTTP request together with a request for upgrading to WebSocket. If the server agrees, the client and server are “connected” and can send messages without needing to establish state — meaning the authorization information, metadata, and so on — with each request-response pair. Think back to our t-shirt store example. With a REST API, you query the database about recent posts when you load the page. But you have no way to receive alerts about new posts without explicitly asking for the posts again. Since REST is stateless, the server can answer your requests, but it doesn’t know you. It can’t send you new posts when they are added to the network. One could imagine solutions for this, such as a refresh button or automatically repeated requests from the client, but none of those give a feeling of real-time interaction. This is the gap that WebSockets fill. Using a WebSocket, you could receive notifications, for example, about new t-shirts being added to the seller’s website.

WebSockets vs. REST

So, what are the differences between REST and WebSocket? To begin, it’s important to understand that they’re of slightly different categories. REST is a style of building APIs, while a WebSocket is a communications protocol. REST’s use of HTTP links the two, though. Let’s explore some of the similarities and differences between REST and WebSockets below, as well as some use cases where one of these platforms is better suited for the task at hand.

Architectures

A common web application that uses a REST API consists of three components: the client (browser), the server, and the database. The server receives the API request and translates it for the database, fetches or changes data in the database, and sends a response. With WebSockets, everything is the same, except you have a special server that’s responsible for communicating via sockets. It’s common to have the HTTP server preprocess incoming connections, which are then moved to that WebSocket server.

Ability to Handle Data and Requests

In some cases, WebSocket can bring certain performance gains over REST. You’ll see this when looking at the differences in client-server messaging in both. In REST, you put all of the state in the header of the message. The server processes that data and your request, and gives you a response. If you have another data request, you have to send the header again to remind the server of who you are. In WebSocket, you send the header once and establish a two-way channel of communication. This means you don’t need to remind the server of who you are and what is the context of your operations, shortening the overall amount of data transmitted. You can open a WebSocket and use it to send messages from the server that tell the client how to modify the page when the user takes certain actions. The result is much faster than loading the pages on each request via REST.

Stateful Versus Stateless

A large difference between WebSocket and REST is that WebSockets are stateful, while REST isn’t. WebSockets are meant for maintaining a bi-directional connection, where each party can send the other messages when they want to. This is impossible to do without establishing some kind of state — in other words, without receiving a response. REST, in contrast, is focused on responding to requests. Each request is stateless, meaning the server is like a  function producing outputs for the client’s inputs. As such, REST is much more suited for infrequent, one-directional, atomic connections.

Performance

Developing with REST is simple and easy. Because it’s so straightforward, there’s not a lot you need to add to the development process to make it run more smoothly. One of the biggest benefits of working with REST is that you don’t need to be hands-on with its management. Developing with WebSockets, in contrast, is much more challenging. This is because you need to manage a stateful system, meaning there are multiple users connected to a server at the same time, with certain statuses, privileges, user groups, and so on. The variables can add some extra labor. However, when you elect to use WebSockets where they’re most applicable, they shouldn’t add a lot of extra complexity that doesn’t already exist in the problem domain. Rather, they’ll simplify things that are typically very difficult. REST is very simple, and some of that is because it’s used for simple things. Therefore, using WebSockets for simple applications will just complicate the development process. But for complicated real-time applications, using WebSockets will be much easier and will offer more flexibility than REST.

Dependencies

Both REST APIs and WebSockets are rather easy to set up and maintain if you don’t develop them from scratch. Since REST APIs are foundational to the modern web, any kind of web framework will enable you to set them up in a trivial amount of time. Though WebSockets are a little bit less popular, there are plenty of libraries for them in most main programming languages. For example, JavaScript has Socket.IO, and Python uses WebSockets. So, if you choose to use WebSockets, you won’t feel a lack of support.

WebSockets vs. REST: Use Cases

Both REST and WebSockets have their use cases where they’re best suited for the job — and others where they’re not as strong. Let’s discuss an instance where you’d want to use each.

When Should You Use REST?

Do you need to get a simple web resource up and running or create a basic API? If so, REST will be enough. REST is well suited to isolated, occasional communications — like creating a basic API, or in a GET request to call RESTful APIs. The simplicity of development will justify any performance downsides —if there are any — that your app might suffer from being stateless.

When Should You Use WebSocket?

If you have an application that needs real-time interaction, or if it has any other events that need to be sent back to users (such as notifications), WebSocket is a tool that can help you manage a lot of the complexity of the process. For a regular application that’s well-served by a stateless, request-response-driven architecture, using WebSocket will be a case of over-engineering and most likely, add unnecessary complexity.

Deciding Between WebSocket and REST

REST and WebSocket are two different technologies that are quite popular and well-supported in the world of software development. REST is the most common way of building APIs. You can find it in virtually every web project, and it is generally the best choice for most simple web projects. But in cases where you’re working with users that need to receive real-time information, like social media updates, real-time analytics, or monitoring data, it’s better to use WebSockets. Now that you’ve seen a comprehensive overview of REST and WebSockets and their strengths, weaknesses, and ideal use cases, you’re prepared to decide which protocol — though technically different — you should use for your next project.

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Janhavi Sathe
Associate Solutions Engineer