When to Use REST vs. SOAP with Examples

by Terence Bennett • January 16, 2024

REST vs. SOAP are two methods of exchanging data through web service APIs (application programming interfaces). They both have unique features that cater to specific use cases. While CIOs indicate that most of the APIs developed today are REST-based, SOAP remains a feasible option under certain circumstances. If you're uncertain about which protocol to utilize for your applications and web services, you've arrived at the right destination. In general, you should use REST for simpler, more flexible, and scalable web services, and SOAP for standardized, protocol-based communication requiring high security and transactional reliability.

Here's the key things to know about SOAP vs. REST:

REST and SOAP are methods for data exchange via web service APIs, with REST being popular due to its simplicity and SOAP favored for its strict standards and security.
SOAP is often preferred for asynchronous and stateful operations, whereas REST is ideal for situations with limited bandwidth and for developing public APIs.
DreamFactory allows users to convert SOAP web services into RESTful APIs, managing the transformed APIs.
The choice between REST and SOAP depends on the specific requirements and context of your applications and web services.

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What Is SOAP?

Microsoft developed SOAP (Simple Object Access Protocol) as a web communication client-server protocol in the 1990s, and it has since been adopted as a web standard.

SOAP can operate via a number of common protocols, such as HTTP (Hypertext Transfer Protocol), SMTP (Simple Mail Transfer Protocol), TCP (Transmission Control Protocol), or UDP (User Datagram Protocol).

One of the breakthroughs of SOAP when it first became available was its platform independence. XML (Extensible Markup Language) is used exclusively for sending SOAP message data, a format understood by all modern systems.

SOAP follows a strict set of standards. Some developers see this as rather inflexible, while others appreciate that it is a well-documented, highly structured option.

What Is REST?

REST (Representational State Transfer) is currently the default choice for most service providers. Unlike SOAP, it is an architectural style for software development.

As SOAP is a protocol and REST is an architecture, comparing them can seem complicated and confusing. The important thing to remember is that, despite their differences, they are both popular ways of transferring data via APIs.

While REST has certain constraints, it also allows for using various languages other than XML. This flexibility simplifies the process of using REST. For example, REST can typically perform requests with a simple URL instead of creating requests with XML.

Although XML can be used with RESTful APIs, it's more common to see JSON used for most public REST APIs. REST requires the use of HTTP or HTTPS (Hypertext Transfer Protocol Secure). It restricts itself to stateless operations, meaning that any web service classified as RESTful does not store the client state on the server.

REST vs. SOAP: What's the Difference?

The main difference between SOAP and REST is that SOAP is a protocol, while REST can be defined as an architectural style. However, the REST API can use the SOAP protocol. It can also use HTTP. Naturally, they will be presented differently, have different functions, and be employed in different scenarios.

Whether you choose to configure your APIs as RESTful APIs using the REST service or use SOAP requests and messaging depends on the application you’re working with. Your programming languages of choice, along with the complexity of your applications (number of endpoints, bandwidth, etc.) will all factor in.

Let’s take a closer look at the pros and cons and determine what would make you choose one over the other in tackling the SOAP vs REST question.

Pros & Cons: REST vs. SOAP

So how do you know when to use REST or SOAP? There are various pros and cons to each that can help you decide.

REST Pros

Despite all these significant advantages, REST is far and away the most popular choice today. Why is this? The answer is that there are some things REST can do that SOAP cannot.

First and foremost, RESTful APIs can make requests via a simple URL. SOAP always sends plain text XML messages, and encoding into the XML format can become tedious, especially with larger data sets. REST works well with JSON, a much more modern and efficient way to work with data.

Nearly all programming languages and scripting languages in use today support the easy import and export of JSON data. On the off-chance JSON doesn't work for your application, REST supports other data formats.

As a lightweight architecture, REST vs. SOAP typically requires less bandwidth. REST is also highly scalable and can keep up with applications and data sets that grow over time. All these advantages have led to RESTful web services being adopted by tech giants and businesses of all sizes.

SOAP Pros

SOAP is both simple and strict. Rather than seeing this as a bad thing, developers who use SOAP appreciate working within its well-documented framework.

The strict regulations lead to increased accuracy in transmitting messages. Collaboration between two systems or organizations is improved because the rules for communication are narrow and set in place. The security around SOAP APIs is one of its strongest points.

SOAP requests have WS Security (Web Services Security) built into the protocol. WS Security provides a layer of security beyond standard mechanisms. HTTPS, for example, only secures messages during transport between a client and server. WS Security secures messages beyond the transport layer and through the entire transaction.

When a web service endpoint receives a SOAP message, it verifies security information in the message header to verify there has been no tampering with message contents. There are other WS extensions that add functionality to SOAP, too, like WSDL (Web Services Description Language).

In a highly regulated scenario, like when transferring data to government organizations, SOAP and WS Security are often seen as the most secure option for transferring a message payload. A host of other WS extensions add optional and well-documented features.

Other SOAP advantages include its support for stateful operations and its ability to use protocols other than HTTP or HTTPS.

REST Cons

While REST APIs have gained popularity due to their simplicity and flexibility, they do have some limitations and drawbacks:

Lack of Standardization: REST does not enforce a strict standard or protocol, which means that implementations can vary widely between different APIs. This can lead to inconsistencies and make it harder for developers to work with multiple REST APIs, as each might have its own conventions and practices.
Limited Security Features: REST relies on the underlying transport protocol (usually HTTP or HTTPS) for security measures, such as authentication and encryption. While this is often sufficient for many applications, it might not be adequate for more complex security requirements, particularly in enterprise settings.
Statelessness: REST APIs are designed to be stateless, meaning each request should contain all the information needed to process it. While this promotes scalability and simplifies server-side implementations, it can also lead to increased complexity on the client side, as clients need to manage and maintain state information.
Limited Error Handling: REST APIs typically use HTTP status codes to communicate errors, which can be limited in expressing the full range of possible issues that might arise during API interactions. This can make error handling and debugging more challenging for developers.

SOAP Cons

In comparison to REST, SOAP can seem like a less flexible option.

SOAP APIs, while well-suited for certain use cases, have some limitations and disadvantages:

Verbosity: SOAP messages are XML-based, which can make them more verbose and complex compared to JSON, the typical format used in REST. This can lead to larger message sizes and slower parsing, which might negatively impact performance, particularly in bandwidth-limited environments.
Complexity: SOAP is a more complex protocol, with a steeper learning curve compared to REST. It has numerous features and specifications, such as WS-Security, WS-ReliableMessaging, and WS-Addressing, which can be difficult for developers to understand and implement correctly.
Limited Flexibility: As a strict protocol, SOAP imposes certain rules and structures on its implementation. This can limit flexibility and make it less suitable for some modern use cases, such as lightweight mobile applications or microservices architectures.
Less Developer-friendly: SOAP APIs can be more challenging to work with, as they often require specialized tools for generating client libraries or handling XML-based messages. Additionally, the widespread adoption of REST has resulted in a larger ecosystem of tools, libraries, and resources tailored specifically for REST API development.

When SOAP Is the Right Choice

When should you use SOAP? There are only two scenarios where SOAP is a clear choice over REST.

Asynchronous operations: An asynchronous operation is very time-specific. It is when various signals or preceding events trigger new events rather than an external timer. REST limits itself to HTTP and HTTPS, neither of which are the ideal communication protocols for this purpose, as they may delay such an operation. SOAP supports additional communication protocols. Asynchronous operations are not suited for very simple or exceptionally complex tasks since it can be difficult to maintain correct timing.

Stateful operations: Performing repetitive, chained tasks such as the financial industry requires means that you may need to retain certain client data within the server for future use. By default, REST is stateless. RESTful apps will not save any previous transactions, but SOAP supports stateful operations. There are many other such use cases for SOAP as well, but most have to do with some variation of these two operations.

When REST Is the Right Choice

While you can use REST to produce many, if not all, of the same results as SOAP with enough work from a professional developer, there are a few situations that REST is specially geared towards.

Limited bandwidth, low-cost or simple operations: Why take the time to write complex XML when you can work from a simple URL to perform a basic, non-repetitive task? Additionally, if you have a lower-income business at the moment or limited bandwidth, REST will perform much faster and give better results in these situations than SOAP.

Developing public APIs: REST is a helpful framework for developing public APIs because it is so common, and therefore it is easy to find other developers who understand it. Additionally, it is highly flexible, bringing lots of options to the marketplace. One example is Gmail, which is a RESTful API. GitHub features public APIs from various developers for various purposes, including health, jobs, cryptocurrency, machine learning, anti-malware, and even the weather, just to name a few.

You can also use REST APIs to import or export content, create and manage credentials, and much more.

Converting SOAP to REST

DreamFactory enables users to transform SOAP to REST by:

Auto-generate RESTful APIs from a WSDL file.
Apply API management features, such as access control and rate limiting, to the transformed APIs.
Handle data transformation between XML (SOAP) and JSON (REST) formats automatically.
Customize the transformation process or add additional logic using DreamFactory's scripting engine.

DreamFactory streamlines the process of converting SOAP web services into RESTful APIs, making it easier to manage, secure, and monitor these APIs. Want to learn more? Start your free trial now or check out an in depth article here.

Manage APIs With DreamFactory

DreamFactory brings a new level of simplicity and speed to the table by enabling you to instantly and easily generate database APIs. We offer powerful security options and take hours or minutes to do what a typical backend engineer may do in a month.

We can also help you simplify workflows and get all the advantages of a secure REST API on top of your SOAP web service. DreamFactory gives an easy process for wrapping any SOAP API in REST.

If you are struggling with when to use REST vs. SOAP, contact DreamFactory today and learn more about what we can do to help you make the right choices for your business. We can also help you get started with your free 14-day trial of our hosted API management platform!

FAQ: When to Use REST vs. SOAP

What is REST used for?

REST (Representational State Transfer) is used for building lightweight, scalable web services, particularly when ease of use, performance, and flexibility are key considerations.

What is SOAP used for?

SOAP (Simple Object Access Protocol) is primarily used for structured, protocol-based data exchange, offering robust security and transactional reliability, making it suitable for enterprise-level web services.

Can REST handle complex operations like SOAP?

While REST can handle a variety of operations, SOAP is generally better for complex transactions due to its standardized protocol and built-in error handling.

Is REST more scalable than SOAP?

Yes, REST is generally more scalable than SOAP due to its stateless nature and lighter data format, making it more efficient for larger numbers of requests.

When should I choose SOAP over REST?

Choose SOAP over REST when your service requires strict security, transactional reliability, and formal contracts between client and server, such as in financial services or enterprise-level applications.