When building or integrating web services, one of the most common decisions developers face is whether to use REST or SOAP. Both approaches allow applications to communicate over a network, but they differ significantly in design, data formats, flexibility, and typical use cases.
In this article, we’ll compare REST and SOAP, look at practical code examples, and explain when each approach makes the most sense.
What Is REST?
REST stands for Representational State Transfer. It is an architectural style for designing web services around resources.
In a REST API, resources are identified by URLs, and standard HTTP methods describe the actions performed on them:
GET — Retrieve a resource
POST — Create a resource
PUT — Replace a resource
PATCH — Partially update a resource
DELETE — Remove a resource
REST APIs commonly use JSON because it is lightweight and easy for both humans and applications to read.
REST Example
Suppose we want to retrieve a user with ID 42.
Request:
GET /api/users/42 HTTP/1.1
Host: example.com
Accept: application/json
Response:
{
"id": 42,
"name": "Mario Rossi",
"email": "mario@example.com"
}
The URL identifies the resource, while the HTTP method indicates the operation.
REST with JavaScript
Here is a simple example using the browser’s fetch() API:
fetch("https://example.com/api/users/42")
.then(response => {
if (!response.ok) {
throw new Error("Request failed");
}
return response.json();
})
.then(user => {
console.log(user.name);
})
.catch(error => {
console.error(error);
});
This example sends an HTTP request, parses the JSON response, and displays the user’s name.
What Is SOAP?
SOAP stands for Simple Object Access Protocol. Unlike REST, SOAP is a formal messaging protocol with a defined XML-based message structure.
SOAP messages are wrapped in an Envelope and contain a Body. They can also include headers for additional information, such as authentication or transaction-related data.
SOAP services are often described using WSDL (Web Services Description Language), which defines the available operations, messages, and data types.
SOAP Example
Let’s retrieve the same user using a SOAP operation called GetUser.
Request:
<soap:Envelope
xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Body>
<GetUser>
<UserId>42</UserId>
</GetUser>
</soap:Body>
</soap:Envelope>
Response:
<soap:Envelope
xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Body>
<GetUserResponse>
<User>
<Id>42</Id>
<Name>Mario Rossi</Name>
<Email>mario@example.com</Email>
</User>
</GetUserResponse>
</soap:Body>
</soap:Envelope>
SOAP uses XML for both requests and responses, which makes the messages more verbose than typical REST responses.
REST vs. SOAP: Key Differences
1. Architecture vs. Protocol
REST is an architectural style based on principles such as statelessness, resource-oriented design, and the use of standard HTTP methods.
SOAP is a protocol with a formal message structure and a collection of related standards.
This distinction is important: REST is not a protocol, and SOAP is not simply “REST with XML.”
2. Data Format
REST can technically use different formats, including JSON, XML, and plain text. However, JSON is the most common choice for modern REST APIs.
SOAP uses XML as its standard message format.
{
"status": "success"
}
The equivalent SOAP-style message is more structured:
<soap:Envelope
xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Body>
<Response>
<Status>success</Status>
</Response>
</soap:Body>
</soap:Envelope>
3. Communication Style
REST typically uses HTTP verbs to represent operations on resources.
GET /users/42
POST /users
PUT /users/42
DELETE /users/42
SOAP usually exposes operations through messages.
<GetUser>
<UserId>42</UserId>
</GetUser>
REST focuses on resources, while SOAP focuses on operations.
4. Performance and Overhead
REST APIs are often easier to consume because JSON messages are generally smaller and require less processing than SOAP XML envelopes.
SOAP messages can be larger because of their XML structure and additional protocol information.
However, performance depends on many factors, including:
Payload size
Network latency
Serialization and parsing
Server implementation
Caching
Authentication mechanisms
REST is not automatically faster in every situation, but it is often a practical choice for lightweight web and mobile applications.
5. Security
Both REST and SOAP can be secured.
REST commonly relies on:
HTTPS
OAuth 2.0
OpenID Connect
JWT-based authentication
SOAP can use HTTPS as well, but it also supports standards such as WS-Security, which can provide message-level security features.
For example, SOAP can include security information inside the message itself, while REST applications often rely on transport security and application-level authentication.
6. Contract and Documentation
REST APIs are commonly documented using OpenAPI.
A simplified OpenAPI example:
openapi: 3.0.0
info:
title: User API
version: 1.0.0
paths:
/users/{id}:
get:
summary: Get a user
parameters:
- name: id
in: path
required: true
schema:
type: integer
responses:
"200":
description: Successful response
SOAP services commonly use WSDL, which provides a formal description of the service contract.
This can be especially useful in enterprise environments where strict contracts and generated client code are important.
REST vs. SOAP: Comparison Table
| Feature | REST | SOAP |
|---|---|---|
| Type | Architectural style | Protocol |
| Common format | JSON | XML |
| Communication | HTTP methods and resources | XML messages and operations |
| Contract | OpenAPI or similar | WSDL |
| Complexity | Usually simpler | Usually more complex |
| Message size | Often smaller | Often larger |
| Caching | Naturally supported through HTTP | More complicated |
| Security | HTTPS, OAuth, JWT, etc. | HTTPS, WS-Security, etc. |
| Typical use cases | Web apps, mobile apps, microservices | Enterprise integrations, legacy systems |
| Learning curve | Generally lower | Generally higher |
When Should You Choose REST?
REST is usually a strong choice when you are building:
A public API
A mobile application backend
A web application
A microservices architecture
A lightweight integration between modern systems
For example, a shopping application might expose endpoints such as:
GET /products
GET /products/123
POST /orders
DELETE /cart/items/123
This resource-oriented structure is easy to understand and works well with standard HTTP tooling.
When Should You Choose SOAP?
SOAP can be the better choice when you need:
A formal service contract
Integration with existing enterprise systems
Compatibility with legacy platforms
Advanced WS-* standards
Message-level security requirements
Enterprise features such as standardized transactions
For example, a banking or insurance system may already expose SOAP services that must be consumed by other applications.
In such cases, using SOAP may be more practical than replacing an established integration.
Can REST and SOAP Work Together?
Yes. REST and SOAP are not mutually exclusive.
A modern application might expose a REST API to mobile clients while communicating with an internal SOAP service.
For example:
Mobile App
|
v
REST API
|
v
Integration Layer
|
v
SOAP Enterprise Service
The integration layer translates REST requests into SOAP messages and converts SOAP responses back into JSON.
This approach allows modern applications to work with legacy systems without requiring a complete rewrite.
REST and SOAP solve similar problems, but they are designed with different priorities.
REST is generally simpler, flexible, and well suited to modern web applications and APIs.
SOAP is more formal and structured, making it valuable for enterprise integrations and systems that depend on established standards.
The best choice depends on your project’s requirements—not simply on which technology is newer.
If you are designing a new API, REST is often a good starting point. If you are integrating with an existing enterprise platform, SOAP may be the right tool for the job.
The goal is not to choose the most popular technology, but the one that best fits your system.