This blog explores the key differences between SOAP and REST APIs, helping you decide which is better suited for your development needs.
What is SOAP?
SOAP is a protocol developed by Microsoft in the late 1990s. It defines a very strict standard for how messages should be formatted and transmitted over a network.
Key Characteristics of SOAP:
- Protocol-based: SOAP is a protocol with a rigid set of rules.
- XML format only: All data in SOAP must be encoded in XML.
- Transport agnostic: It can use protocols like HTTP, SMTP, TCP, etc.
- Built-in error handling: SOAP supports standardized error reporting.
- Security features: SOAP supports WS-Security for advanced security needs.
- Tightly coupled: Changes in one system can require updates in the other.
When to Use SOAP:
SOAP is best for enterprise-level applications that require high reliability, strict security (such as financial or health data), and standardized protocols. It’s still widely used in legacy systems and B2B communication.
What is REST?
REST is an architectural style introduced by Roy Fielding in 2000. It is more flexible and lightweight compared to SOAP, and has become the most popular standard for designing modern web APIs.
Key Characteristics of REST:
- Architecture style: REST is not a protocol but a set of architectural guidelines.
- Supports multiple formats: REST can return data in JSON, XML, HTML, or plain text (JSON is most common).
- Uses standard HTTP methods: GET, POST, PUT, DELETE, etc.
- Stateless: Each request contains all the information needed to process it.
- Scalable and fast: REST is known for being lightweight and suitable for web and mobile applications.
When to Use REST:
REST is ideal for public APIs, cloud applications, mobile apps, and services where performance and scalability are essential.
SOAP vs REST API: Feature Comparison
| Feature | SOAP | REST |
| Protocol | Strict protocol | Architectural style |
| Message format | XML only | JSON, XML, HTML, Plain Text |
| Transport | HTTP, SMTP, TCP, etc. | HTTP/HTTPS only |
| Performance | Slower due to XML parsing | Faster and lightweight |
| Security | WS-Security (built-in) | SSL/TLS + custom authentication |
| Ease of use | More complex | Simple and intuitive |
| Error handling | Standardized fault handling | Custom implementation |
| Caching | Not supported | Supported via HTTP headers |
| Statefulness | Stateful or stateless | Stateless |
| Tooling support | Strong in enterprise (e.g., WSDL) | Widespread with RESTful libraries |
Which One Should You Choose?
Choose SOAP if:
- You are working with legacy systems that require SOAP.
- Your application requires strong security and transaction compliance.
- You need strict contracts (e.g., WSDL) and formal definitions.
- The industry you’re in demands high-level reliability and security (e.g., banking, healthcare, telecom).
Choose REST if:
- You are developing a web or mobile app.
- You want to use lightweight data formats like JSON.
- You need your service to be scalable, fast, and easy to consume.
- Your project requires frequent updates and agile development.
Real-World Use Cases
- SOAP: Banking systems, airline booking services, healthcare systems.
- REST: Twitter API, Google Maps API, Spotify, GitHub, and virtually all modern mobile apps.
Conclusion
While both SOAP and REST APIs serve to connect different systems and facilitate data exchange, the best choice depends on your specific needs. SOAP is great for enterprise-grade, secure, and reliable operations, whereas REST is best for performance-oriented, easy-to-maintain, and web-based services.
In 2025, REST continues to dominate the API landscape due to its simplicity and compatibility with the cloud and mobile-first world. However, SOAP is far from obsolete—it still has a place in many mission-critical systems.
Understanding the differences between SOAP and REST is essential for developers, architects, and anyone involved in building or consuming APIs. Choose wisely, and you’ll ensure your application’s architecture is scalable, secure, and future-ready.
Read more on https://keploy.io/blog/community/soap-vs-rest-choosing-the-right-api-protocol