REST vs. SOAP: A Comprehensive Comparison

When it comes to web services and APIs, two major communication protocols dominate the landscape: REST (Representational State Transfer) and SOAP (Simple Object Access Protocol). Both serve the same fundamental purpose—enabling communication between different systems over a network—but they differ significantly in structure, implementation, and use cases.

What is REST?

• Rest stand for Representational State Transfer
• REST is an architectural style designed to facilitate communication between web-based systems. It follows a stateless approach, meaning that each request from a client to a server contains all necessary information, and the server does not store any client state between requests.

REST is an architectural style defined by Roy Fielding in his 2000 doctoral dissertation. It outlines 6 key constraints:

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

Representational State Transfer

Lets break it

Representational

This means you don’t interact with the actual data or resource, but rather a representation of it.

• The resource could be a user, image, blog post, etc.
• The representation is typically in JSON, XML, HTML, etc.

Example : This JSON is a representation of a user resource.

{
  "id": 123,
  "name": "John Doe"
}

State

State refers to the current situation or data about the resource at a given time.

• When you GET /users/123, you are retrieving the current state of user 123.
• When you PUT /users/123, you are changing the state of user 123.

You transfer states of resources between client and server.

Transfer

This is about moving data between client ↔ server over a network (usually HTTP).

• Client makes a request.
• Server sends back a representation of the resource’s state.

So you’re transferring the representation of a resource’s state.

Putting it all together:

In REST, the client and server communicate by transferring representations (like JSON) of the current state of resources (like users, orders, etc.).

Key Features of REST

• Uses HTTP Methods: GET, POST, PUT, DELETE, PATCH
• Lightweight: Typically returns data in JSON or XML format
• Stateless: Each request is independent and does not rely on previous interactions
• Scalable: Designed for high-performance distributed systems
• Flexible: Can work with different types of data formats (JSON, XML, YAML, etc.)

Advantages of REST

• Simplicity: Uses standard HTTP methods, making it easy to implement and understand.
• Performance: JSON-based responses are lightweight and faster to process than SOAP’s XML.
• Scalability: Statelessness allows for better load balancing and horizontal scaling.
• Cacheability: Responses can be cached, improving efficiency.

Disadvantages of REST

• Lack of built-in security: Security must be manually implemented (e.g., OAuth, JWT).
• Limited built-in error handling: Unlike SOAP, REST does not have a standardized error handling mechanism.

Why is it called RESTful?

• The term RESTful comes from REST + ful
• A RESTful API is one that fully respects the rules or constraints of REST.
• RESTful is typically used to refer to web services implementing such an architecture(REST).

What is SOAP?

• Soap stands for Simple Object Access Protocol
• SOAP is a protocol for exchanging structured information in web services. It relies on XML-based messages and follows strict communication standards. Unlike REST, SOAP maintains stateful communication if needed.

Key Features of SOAP

• Protocol-Based: Uses XML messaging format over HTTP, SMTP, TCP, or other transport protocols.
• Strict Standards: Includes WS-Security, WS-ReliableMessaging, and other enterprise-grade security features.
• Supports ACID Transactions: Ensures atomicity, consistency, isolation, and durability.
• Built-in Error Handling: Uses standardized error codes and fault messages.

Advantages of SOAP

• High Security: Ideal for financial, healthcare, and enterprise applications that require strict security.
• Reliability: Built-in mechanisms for message acknowledgement and retries.
• Extensibility: Supports additional web service specifications like WS-Security and WS-Addressing.
• Works Beyond HTTP: Unlike REST, SOAP can use other transport protocols like SMTP and TCP.

Disadvantages of SOAP:

• Complexity: More difficult to implement due to XML formatting and strict specifications.
• Slower Performance: XML messages are bulkier than JSON, making SOAP slower than REST.
• Less Flexibility: Limited to XML format, whereas REST supports multiple formats.

REST vs. SOAP

Which One Should You Choose?

• Use REST if you need a lightweight, fast, and scalable API for web and mobile applications. It’s ideal for public APIs, microservices, and modern web applications.
• Use SOAP if your application requires high security, reliability, and strict compliance with enterprise-level standards, such as in banking, healthcare, or B2B transactions.

Understanding “Architectural Style” vs. “Protocol”

When comparing REST and SOAP, a key difference is that REST is an architectural style, while SOAP is a protocol. But what does that actually mean? Let’s break it down.

What is an Architectural Style?

An architectural style is a set of design principles and guidelines that define how systems should be structured and interact. It provides general rules but allows flexibility in implementation.

REST as an Architectural Style

• REST is not a strict standard; it is a set of design principles for building web services.
• It is stateless and relies on standard HTTP methods like GET, POST, PUT, DELETE.
• REST does not enforce a specific format; you can use JSON, XML, YAML, etc.
• RESTful APIs can be implemented in different ways as long as they follow REST principles.

Example: REST is like a blueprint for designing APIs, but developers have flexibility in how they implement it.

What is a Protocol?

A protocol is a strict set of rules and formats that define how data should be transmitted and processed between systems. It ensures standardization and interoperability between different platforms.

SOAP as a Protocol

• SOAP is a well-defined messaging protocol with a strict XML-based format.
• It has built-in security (WS-Security), error handling, and supports ACID transactions.
• SOAP enforces a specific structure for messages, headers, and responses.
• It works over multiple transport protocols (HTTP, SMTP, TCP, etc.), making it more versatile for enterprise applications.

Example: SOAP is like a fixed set of rules that must be followed to ensure reliable communication between different systems.

Architectural Style vs. Protocol – A Simple Analogy

Imagine You Are Sending a Letter

REST (Architectural Style) = The Concept of Mailing a Letter

• Think of REST as the general concept of mailing letters.
• There are different ways to send a letter: by post, by courier, or even by hand.
• You can write your letter in any language (English, Spanish, French, etc.), just like REST allows different data formats (JSON, XML, etc.).
• You follow some basic rules (like writing an address, putting a stamp), but there’s flexibility in how you send it.

SOAP (Protocol) = A Strict Mailing Service Like FedEx

• SOAP is like a specific mailing service (e.g., FedEx, DHL) that follows strict rules.
• You must fill out specific forms, use a predefined envelope, and follow detailed procedures.
• Your letter must be written in a specific format, just like SOAP messages must be in XML.
• It ensures security, tracking, and reliability, just like SOAP ensures security and structured communication.

Why Do We Compare REST and SOAP?

We compare REST and SOAP because they serve the same purpose—web communication—even though they achieve it differently (one is a style, and the other is a protocol).

• Both Are Used for Web Services → They define how applications communicate over a network.
• Both Compete for the Same Purpose → Developers choose between REST and SOAP when building APIs.
• Both Work Over HTTP → Even though SOAP can use other protocols like SMTP and TCP, it is most commonly used over HTTP, just like REST.

Why Not Compare SOAP with HTTP or FTP?

• HTTP, HTTPS, and FTP are transport protocols → They define how data is transmitted.
• SOAP is a messaging protocol → It defines how data should be formatted and processed in a web service.

Example:

• HTTP/HTTPS is like a road (it moves the data).
• SOAP is like a truck carrying goods (it defines how the data is structured).
• REST is like a traffic system that provides rules for organizing roads and vehicles efficiently.

Conclusion

Both REST and SOAP have their strengths and weaknesses. REST is the go-to choice for modern web applications due to its simplicity and speed, while SOAP remains valuable for secure, enterprise-level transactions. Choosing the right protocol depends on your specific requirements, such as security, performance, and compatibility needs.

Resouces

• API Maturity Model
• Codecademy
• Rest vs Restfull
• SOAP vs Rest – javapoint
• SOAP vs Rest -Upwork