SOAP vs REST API (Clear Different)

You’ll find Application Programming Interfaces (APIs) in use all over the internet. Various systems use them to send information from one piece of software to another. Simple Object Access Protocol (SOAP) and Representational State Transfer (REST) are commonly-used API styles.

What are these two protocols and how are they different? Find out when you should use each and what their relative advantages are.

What Is a SOAP API?

SOAP is a format that uses web service description language (WSDL) to describe an underlying API. It’s structured around the extensive markup language (XML). It supports both stateful and stateless data exchange between services.

In its stateful form, SOAP ensures that data exchange is protocol-based. It also tracks request history and maintains the integrity of each request in a chain. This is one of the reasons why SOAP remains a valuable API style in many top tech companies. SOAP doesn’t leave the job of session tracking to the client but handles it itself.

Security-wise, the SOAP protocol relies on web service (WS) security and secure socket layers (SSL). Data sent over SOAP is end-to-end encrypted. So, it’s a good idea to use SOAP when extra layers of security, rather than functionality, are the goal.

What Is a REST API?

REST is the more modern form of API. Unlike SOAP, it’s not protocol-bound. It focuses on architecture instead. So it comes with far greater flexibility—one reason it’s becoming the mainstay API style across the internet.

REST only sends a description of the state of a data source to a requesting web service, via an endpoint. Thus, data processing and transfer are lighter and faster using REST.

The REST API style is also strictly stateless by default. It hands over the job of session tracking and request chaining to the client and focuses on maintaining operations and resources.

Ultimately, the entire REST architecture is easy to use. And data exchange is mostly in JavaScript Object Notation (JSON) format, a more language-agnostic form of information exchange.

Where Is REST Applicable?

Most modern applications and websites that you use today rely on the REST API style. Typically, the REST architecture finds its application in services that focus more on performance and speed.

In addition to its support for JSON, REST also supports other data formats, including XML, PrettyJSON, and HTML. REST is scalable, flexible, mutable, and accessible. These are some of the core attributes that give it an upper hand as a tool for data exchange.

With its simplicity and statelessness, you’ll find REST in social media apps, enterprise, and cloud-based applications.

Its ease of integration and error-handling capability mean that it’s easy to grab data for your application from REST. Building a dynamic frontend application around a REST API is often less strenuous.

When Should You Use SOAP?

Although old, SOAP APIs are still very much in use today. While SOAP is more rigid and protocol-driven, it’s an API style that apps handling online transactions often prefer.

Although it can be equally stateless, SOAP doesn’t compete when it comes to performance. The main reason behind this is that it transfers entire resources rather than smaller representations of them.

But the stateful nature of SOAP, which makes it memory efficient, is one of its selling points. Additionally, it conforms with the ACID (atomicity, consistency, integrity, and durability) rules. This also explains its ability to maintain request activity in memory.

Because of its heavyweight structure, it’s almost pointless to handle stateless requests with SOAP. REST handles such functionality far more easily.

So, if you’re building an app that can handle multiple financial transactions, or more confidential data, SOAP might be the best option. But other software like cloud and social media apps that need light caching and speed don’t sit well so on SOAP.

Key Differences Between SOAP and REST

So what are the differences between SOAP and REST? Let’s take a look at them:

1. Data Format

SOAP relies on WSDL for sending data as an XML document. REST supports many data formats, including JSON, HTML, and XML.

2. Request Structure

For the desired response, each API style has its own request format.

SOAP’s request architecture is similar to the structure of an HTML document. And it has the following parts:

• The envelope: Defines the nature of the incoming SOAP data. Ultimately, it informs a recipient that it’s in XML.
• Header: Carries extra information about the SOAP API. This can include authentication and connection tokens.
• Request body: Describes the main content of the request. Hence, it validates the information contained in the response.
• Fault: Details potential error information within the SOAP API.

Here’s what the message structure of a REST API looks like:

• API endpoint: A connector linking to a particular resource within the application or data provider.
• Request method: Defines the type of request coming from an application. These could be POST, GET, PUT, or DELETE.
• Headers: Details the content type, authentication tokens, and maybe more, depending on the API provider’s specifications.
• Body: Also called the request payload. It describes the information you want to retrieve from or send to the REST API.

3. Caching and State Handling

REST, unlike SOAP, doesn’t handle caching. This can be a disadvantage when tracking request history in a more complex transactional chain. Although SOAP is also stateless by default, it supports stateful transactions too. So it’s ideal for tracking request history.

4. Security

In addition to SSL, SOAP uses the WS security extension to provide end-to-end encryption during data exchange. REST relies heavily on HTTPS for security. Additionally, the compliance of SOAP with the ACID guideline makes it protocol-bound. REST isn’t ACID-compliant but architecture-based, without specific rules.

5. Performance and Speed

Unlike the SOAP protocol, the REST architecture is lightweight. So it offers better performance and speed during data transfer.

6. Ease of Integration

It’s easier to modify schemas in REST. This makes integration a breeze while connecting to a REST API. SOAP is rigid and requires that you follow set protocols for successful integration.

7. Community Support and Learning Curve

REST is more popular than its SOAP counterpart. It offers better community support and​​ has an easier learning curve than the more complex SOAP protocol.

Make Your API Choice

SOAP and REST are two indispensable tools in the software industry. Regardless of the perception of their approaches, each has specific areas of application. Although REST is more popular, some companies combine both API styles to get the best of both.