SOAP vs REST API: What's the Difference and Which Should You Choose?

In the world of web services and software integration, SOAP and REST are two dominant API architectures that developers frequently use. While both serve the same primary purpose—enabling communication between different systems—they do so in very different ways.

If you’re building an application that communicates with external services or internal systems, understanding the difference between SOAP vs REST API is crucial for making the right architectural decision.

In this blog, we’ll break down SOAP and REST, compare their features, highlight their pros and cons, and help you decide which one is best suited for your project.

 

What Is an API?

An API (Application Programming Interface) allows two software systems to communicate with each other. APIs can be used for tasks like retrieving data, processing transactions, or integrating third-party services like payment gateways, social logins, and more.

Two of the most widely used API protocols are:

• SOAP (Simple Object Access Protocol)
  
  


• REST (Representational State Transfer)
  
  

 

What Is SOAP?

SOAP is a protocol developed by Microsoft in the late 1990s. It defines a set of strict rules for structuring messages and relies heavily on XML for data formatting.

Key Features of SOAP:

• Protocol-based and highly structured
  
  


• Uses XML for request and response formatting
  
  


• Operates over HTTP, SMTP, TCP, and more
  
  


• Includes built-in standards for security (WS-Security), transactions, and messaging reliability
  
  


• Requires a WSDL (Web Services Description Language) file to define the interface
  
  

Advantages of SOAP:

• High security: Ideal for enterprise-level applications like banking and healthcare
  
  


• Standardization: Well-defined standards for error handling, messaging, and data types
  
  


• Strong support for ACID compliance: Good for distributed transactions
  
  


• Protocol agnostic: Can work over multiple transport protocols beyond HTTP
  
  

Disadvantages of SOAP:

• Verbose XML format: Slower and requires more bandwidth
  
  


• Complexity: Requires more setup and configuration
  
  


• Less flexibility for modern web and mobile applications
  
  

What Is REST?

REST is an architectural style introduced by Roy Fielding in 2000. Unlike SOAP, REST is not a protocol but a set of guidelines that leverage standard HTTP methods (GET, POST, PUT, DELETE).

Key Features of REST:

• Stateless and cacheable
  
  


• Uses standard HTTP verbs
  
  


• Data can be in JSON, XML, YAML, or even plain text (JSON is most common)
  
  


• Lightweight and easier to integrate with web applications
  
  

Advantages of REST:

• Faster and lightweight: JSON is smaller and easier to parse than XML
  
  


• Easy to use and understand: Especially for web developers
  
  


• Better performance on mobile and web platforms
  
  


• Scalable and flexible
  
  

Disadvantages of REST:

• Less standardized than SOAP
  
  


• No built-in security: Relies on HTTPS and external security implementations
  
  


• Not ideal for complex transactions or guaranteed delivery
  
  

SOAP vs REST API: Side-by-Side Comparison

Feature	SOAP	REST
Type	Protocol	Architecture style
Format	XML only	JSON, XML, YAML, plain text
Transport	HTTP, SMTP, TCP, etc.	HTTP only
Message Definition	WSDL (strict contract)	No formal contract
Flexibility	Rigid and standardized	Flexible and lightweight
Performance	Slower due to XML parsing	Faster with smaller payloads
Security	WS-Security, built-in	HTTPS and third-party mechanisms
Use Cases	Enterprise apps, banking, legacy systems	Mobile apps, web apps, microservices

When to Use SOAP

SOAP is best when:

• Security is critical: Such as financial or healthcare data
  
  


• You need strict contracts and formal definitions of service
  
  


• Your application involves stateful operations or multi-step transactions
  
  


• You're working in enterprise environments or integrating with legacy systems
  
  

When to Use REST

REST is ideal when:

• You’re building a modern web or mobile application
  
  


• You want fast and lightweight communication
  
  


• You prefer flexibility in data formats (especially JSON)
  
  


• You’re working with microservices or cloud-native applications
  
  

Real-World Examples

• SOAP is still commonly used in enterprise-level applications like:
  
  
  
  
  
  • Payment gateways (e.g., PayPal's classic APIs)
    
    
  
  
  • Telecommunication services
    
    
  
  
  • Government portals
    
    
  
  
  
  


• REST dominates in modern development:
  
  
  
  
  
  • Twitter, Facebook, and GitHub APIs
    
    
  
  
  • Mobile apps and SPAs (Single Page Applications)
    
    
  
  
  • E-commerce APIs (like Shopify or Stripe)
    
    
  
  
  
  

Conclusion

When comparing SOAP vs REST API, there’s no one-size-fits-all answer. Both have their strengths and ideal use cases. While SOAP is powerful, secure, and suitable for enterprise systems, REST is simpler, faster, and better aligned with today’s web and mobile development trends.

In short:

• Use SOAP when you need high security, strict standards, and protocol flexibility.
  
  


• Use REST when you need simplicity, speed, and scalability for modern applications.
  
  

Understanding the difference between SOAP and REST APIs helps you make informed decisions when building or integrating web services, ensuring your system is both effective and maintainable.

Need help choosing the right API protocol for your application? Let us know your use case, and we’ll guide you with expert recommendations.

Read more on- https://keploy.io/blog/community/soap-vs-rest-choosing-the-right-api-protocol