Overview
In modern integration scenarios — especially in Salesforce integrations — knowing the difference between SOAP and REST is essential. Both are approaches to building web services, but they differ in design philosophy, message formats, transport, and typical use cases. This post explains the core differences, pros and cons, security considerations, and when to choose one over the other.
Key differences (at a glance)
– Architectural style: REST is an architectural style that uses standard HTTP verbs (GET, POST, PUT, DELETE). SOAP is a protocol that defines a strict messaging format (XML-based) and operations.
– Message format: REST commonly uses JSON (but can use XML). SOAP uses XML exclusively with a defined envelope and schema.
– Transport: REST typically uses plain HTTP/HTTPS. SOAP can use HTTP/HTTPS, SMTP, TCP — but is most often run over HTTP/S.
– State: REST is stateless by design. SOAP supports stateful operations (via WS-* extensions) if needed.
Detailed comparison
1. Protocol vs Architectural Style
SOAP (Simple Object Access Protocol) is a protocol with formal standards (WS-Security, WS-Addressing, WS-ReliableMessaging). REST (Representational State Transfer) is an architectural style that leverages HTTP and resource-based URIs.
2. Payload and Performance
SOAP messages are wrapped in verbose XML envelopes, which can add overhead. REST typically exchanges lightweight JSON payloads, which are smaller and parse faster, leading to better performance for web/mobile apps.
3. Standards and Features
SOAP provides built-in standards for security (WS-Security), transactions, and reliable messaging. REST relies on underlying transport (HTTPS) and additional layers (OAuth, JWT) for security and lacks many built-in enterprise features that SOAP provides.
4. Caching and Idempotency
REST leverages HTTP caching semantics (Cache-Control, ETag) and is well-suited for idempotent operations using GET/PUT/DELETE. SOAP does not have native HTTP caching rules because messages are typically POSTed to a single endpoint.
5. Tooling and Contracts
SOAP uses WSDL (Web Services Description Language) to provide a strong contract, enabling code generation and strict validation. REST can use OpenAPI (Swagger) for documentation and client generation, but REST is generally more flexible and less rigidly defined.
Examples
SOAP request (simplified):
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:urn="urn:examples:helloservice">
<soapenv:Header/>
<soapenv:Body>
<urn:sayHello>
<name>John</name>
</urn:sayHello>
</soapenv:Body>
</soapenv:Envelope>
REST request (GET example):
GET /api/accounts/001xx000003DGbYAAW HTTP/1.1
Host: your-instance.salesforce.com
Authorization: Bearer <access_token>
Accept: application/json
When to use SOAP
– You need advanced WS-* features (WS-Security, reliable messaging, transactions).
– The integration partner requires a strict contract and WSDL-based integration.
– You’re working with legacy enterprise systems that expose SOAP endpoints.
When to use REST
– Building web or mobile applications where low bandwidth and performance matter.
– You prefer simpler, resource-oriented APIs with JSON payloads.
– You want to leverage HTTP features like caching, content negotiation, and easy browser compatibility.
Security considerations
– SOAP: Use WS-Security for message-level security (signing, encryption) when end-to-end message protection is required.
– REST: Use HTTPS (TLS) for transport security and standards like OAuth 2.0 / JWT for authentication and authorization.
Salesforce-specific notes
– Salesforce supports both SOAP and REST APIs. The SOAP API provides a WSDL, strong typing, and is useful for bulk and metadata operations in certain contexts. The REST API is ideal for simpler integrations, mobile apps, and integrations where JSON is preferred.
Summary: which one to pick?
Choose SOAP when you need formal contracts, advanced enterprise features, or are integrating with systems that require SOAP. Choose REST when you want simplicity, performance, and better support for web/mobile clients. In many Salesforce projects, REST is the default for new integrations, with SOAP used for legacy or specialized enterprise scenarios.
Quick checklist
– Need WS-* and message-level security: SOAP
– Mobile/web lightweight JSON: REST
– Strong contract + code generation: SOAP (WSDL) or REST (OpenAPI)
– Cache and use HTTP semantics: REST