Difference Between REST API and SOAP API

SOAP API and REST API are both popular methods for exchanging data between two applications. Quite often, these two are mistakenly considered to work the same way. But there are some differences. Read on! 

What is a REST API?

REST API is an API that uses HTTP requests to manipulate data. And because it's based on the principles of REST, or Representational State Transfer, it's designed to be scalable and efficient.

REST APIs are all about ease of use. There are no complicated protocols to learn, and you can use any programming language you want. Plus, they're perfect for mobile applications, since they're lightweight and don't require a lot of bandwidth.

What is SOAP API?

A SOAP API is an application programming interface that uses the Simple Object Access Protocol to exchange messages.

SOAP API messages are XML-based, and they are popular among enterprise systems because they offer a lot of features and functionality.

But there's a downside: SOAP APIs can be difficult to use. .

SOAP API vs. REST API: the important differences

At a high level, the main difference between SOAP API and REST API is that SOAP API uses XML while REST API uses JSON. However, there are many other differences that you should be aware of before deciding which among the two you should use for your next project.

Here are the rest of the differences: 

1. Data formats

SOAP uses XML as its data format, while REST uses JSON. XML is more verbose than JSON, so it takes up more bandwidth. But it's also more versatile, because it can be used to describe a wider range of data structures. JSON is more widely supported, because it's been around longer.

2.  Cache

SOAP is not cacheable at the HTTP level, while REST is. What does this mean for you as a developer?

Simply put, it means that if you're using a SOAP API, your calls to the server will always go through, no matter how often you make them. This can lead to a lot of unnecessary network traffic and can slow down your app.

On the other hand, if you're using a REST API, the server will cache your calls, meaning that it will keep the results of your previous requests and deliver them to you faster. This can result in a more responsive app and a better user experience.

3. Bulkness

REST API is more lightweight and faster than SOAP API. This is obviously because SOAP API uses XML messages to communicate between the client and server, while REST API relies on HTTP requests.

REST API is generally more lightweight and faster than SOAP API. This is obviously because SOAP API uses XML messages to communicate between the client and server, while REST API relies on HTTP requests. XML is a great format for data exchange, but it is relatively verbose and can add significant overhead to message size. HTTP, on the other hand, is a simple request/response protocol that is much less likely to introduce errors. 

4. Rule strictness

SOAP API follows a stricter set of rules, while REST API is more flexible. This means that with SOAP API, you have to adhere to a specific structure when sending and receiving messages, while with REST API you can be more creative with the way you format your requests and responses. SOAP follows a strict set of standards to allow communication between the server and the client. 

On the other hand, REST API is an architectural style and as such, has no official standard but follows six constraints which are:

• Uniform Interface
• Client-Server
• Stateless
• Cacheable
•  Layered System
• Code on Demand

5. Client-server relationship

SOAP API is a client-server model, while REST API is a distributed system. What does that mean? In a nutshell, it means that with SOAP API, the client initiates the communication and the server responds. With REST API, on the other hand, communication is bi-directional — each resource on the server can be accessed using a uniform resource identifier (URI), which means that clients don't need to know anything about the server's internal structure. This makes REST more efficient and scalable than SOAP.

6. Resource requirements

SOAP API needs to convert the data into XML, making it demand more resources. This in turn increases its payload leading to large-sized files. On the other hand, REST API is not restricted to XML and uses multiple standards, and requires fewer resources. Therefore, comparing the processing of the two, REST API is faster than SOAP API.

7. JavaScript implementation

Although SOAP API is convenient with JavaScript, it does not support greater implementation. REST API, on the other hand,  can be implemented easily and as such, it is more convenient with JavaScript.

Although SOAP API is convenient with JavaScript, it does not support greater implementation. REST API, on the other hand,  can be implemented easily and as such, it is more convenient with JavaScript. .

8. Services interface

SOAP API and REST API express business logic in different ways. SOAP API uses a service interface like @WebService which can lead to more boilerplate code.  However, it also can provide more control over how the business logic is expressed. REST API deploys URL exposure like @Path, which can lead to more concise code. However, it can also make the business logic more difficult to understand. 

9. Code on demand

With SOAP, the client has to download and install all of the code required to access the web service. But with REST, only the code needed at that moment is sent from the server to the client.

10. Security

SOAP API has more security features by default than REST API. For example, WS-Security is a standard protocol used in SOAP API that adds default security headers to each message like UsernameToken and Timestamp. Therefore, SOAP API is preferred over REST API in most cases where a high level of security is crucial. Good examples of popular use cases include Card Numbers, Passwords, and Bank accounts. On the other hand, REST API uses HTTPS for security.

11. Complexity

Finally, SOAP is more complex than REST, and requires more coding on the part of the developer. So if you're not familiar with XML or HTTP headers, then you'll probably have an easier time working with REST.

Conclusion

SOAP is generally used for enterprise-level applications and it’s more difficult to implement. REST, on the other hand, is a light API protocol and this is why it’s more popular than SOAP because it's faster and simpler to use. So if you're just starting out with APIs, we would recommend going with REST API. It's much easier to work with compared to SOAP. And if you ever need to switch to SOAP in the future, the transition will be much smoother.