SOAP vs REST — Key Differences Explained

Posted by Vinay Vernekar 17th January 2026

Introduction

SOAP and REST are two widely used approaches for building web services and APIs. Understanding their core differences is essential for architects, developers, and Salesforce professionals working with integrations. This post explains SOAP vs REST, highlights use-cases, and provides clear examples to help you choose the right approach.

High-level Differences

1. Protocol vs Architectural Style

SOAP (Simple Object Access Protocol) is a protocol with strict standards. It defines a formal message structure, rules for encoding, and relies on XML. REST (Representational State Transfer) is an architectural style that uses standard web protocols (HTTP) and can exchange data in multiple formats (JSON, XML, etc.).

2. Transport and Payload

SOAP commonly uses HTTP, SMTP, TCP and always uses XML for message format. REST typically uses HTTP and supports multiple formats (JSON is the most popular for modern APIs), making it lighter and faster in many cases.

3. Operations and Semantics

SOAP exposes operations (methods) through a contract (WSDL) and supports RPC-style or document-style interactions. REST treats resources (nouns) and uses standard HTTP verbs to operate on them: GET, POST, PUT, PATCH, DELETE.

4. Standards and Extensibility

SOAP has built-in standards for security (WS-Security), transactions, reliable messaging, and formal contracts (WSDL). REST relies on transport-level security (HTTPS) and standards like OAuth for authorization but lacks formal built-in standards for things like transactions.

5. Tooling and Contracts

SOAP uses WSDL to describe the service contract which enables strong typing, automatic client generation, and strict validation. REST APIs often use OpenAPI (Swagger) or RAML for documentation and client generation, but the contract is generally less strict compared to WSDL.

When to Use SOAP

  • Enterprise systems that require formal contracts and WS-* standards (e.g., banking, telecom).
  • When built-in support for transactions, reliability, or advanced security is required.
  • Legacy systems that already depend on SOAP/WSDL.

When to Use REST

  • Public APIs and microservices where simplicity, performance, and scalability matter.
  • Mobile or web clients that prefer lightweight payloads (JSON).
  • Rapid development and systems that favor HTTP semantics and caching.

Example Messages

SOAP Request (simplified)

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:ns="http://example.com/ns">
  <soapenv:Header/>
  <soapenv:Body>
    <ns:GetAccount>
      <ns:AccountId>12345</ns:AccountId>
    </ns:GetAccount>
  </soapenv:Body>
</soapenv:Envelope>

REST Request (HTTP GET)

GET /api/accounts/12345 HTTP/1.1
Host: api.example.com
Accept: application/json
Authorization: Bearer <token>

Pros and Cons (Summary)

SOAP Pros

  • Formal contracts (WSDL), strong typing.
  • Built-in WS-* standards for security and reliability.
  • Good for complex enterprise scenarios.

SOAP Cons

  • Verbose (XML heavy), steeper learning curve.
  • Can be slower due to larger payloads and processing.

REST Pros

  • Lightweight (JSON), easy to use with web and mobile clients.
  • Leverages HTTP semantics (caching, verbs) for scalability.
  • Faster to develop and widely adopted for public APIs.

REST Cons

  • No standard for transactions or advanced reliability out-of-the-box.
  • Security standards are implemented at application level (e.g., OAuth).

Conclusion

Choose SOAP when you need formal contracts, advanced WS-* features, or are integrating with legacy enterprise systems. Choose REST when you want simplicity, performance, and broad client compatibility — ideal for modern web and mobile APIs. In Salesforce integrations, SOAP APIs (SOAP API, Apex SOAP) are useful when WSDL-based contracts are needed, while REST APIs (REST API, Apex REST) are preferred for lighter-weight, JSON-driven integrations.

Keywords: SOAP vs REST, SOAP REST differences, web services, APIs, WSDL, JSON, WS-Security

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