Overview
Web services are standardized ways for systems to communicate over a network (usually the Internet). They expose application functionality or data as network-accessible endpoints so different applications, platforms, or devices can interoperate regardless of implementation language or technology stack. Web services form the backbone of modern integration patterns — powering APIs, microservices, mobile back ends, and cross-platform integrations.
Key characteristics
Web services typically have these characteristics:
- Network-accessible: Communicate over HTTP/HTTPS or other network protocols.
- Platform and language agnostic: Clients and servers can be implemented in different languages.
- Standardized message formats: Use XML, JSON, or other agreed-upon formats.
- Discoverable and documented: Descriptions (WSDL/OpenAPI) make it easier for clients to discover capabilities.
- Stateless or stateful: Most modern web services are designed to be stateless for scalability.
Common types of web services
There are two broad families commonly discussed:
1) SOAP Web Services
SOAP (Simple Object Access Protocol) is a protocol that relies on XML for message format and often uses WSDL (Web Services Description Language) to describe service operations. SOAP is feature-rich and supports built-in standards for security (WS-Security), transactions, and reliable messaging.
Use-cases: enterprise systems requiring strong contracts, formal schemas, and advanced security or transaction support.
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Body>
<GetCustomerRequest xmlns="http://example.com/soap">
<CustomerId>12345</CustomerId>
</GetCustomerRequest>
</soap:Body>
</soap:Envelope>
2) RESTful Web Services
REST (Representational State Transfer) is an architectural style rather than a protocol. RESTful services commonly use HTTP methods (GET, POST, PUT, DELETE) and exchange data in JSON or XML. They are typically simpler and more lightweight than SOAP and are widely used for web APIs and microservices.
Use-cases: public APIs, mobile back ends, microservices, and scenarios where simplicity, performance, and JSON payloads matter.
curl -X GET "https://api.example.com/customers/12345" -H "Accept: application/json"
// Response (JSON)
{
"id": 12345,
"name": "Acme Corp",
"industry": "Manufacturing"
}
Other related concepts
WSDL (for SOAP) and OpenAPI/Swagger (for REST) provide machine-readable contract descriptions. Authentication and authorization are typically handled by OAuth, API keys, JWTs, or HTTP Basic/Auth. Transport security is commonly provided by HTTPS.
When to choose which?
Choose SOAP when you need strict contracts, WS-* features, or enterprise-level reliability/security. Choose RESTful/HTTP APIs when you need lightweight, scalable, and easy-to-consume endpoints — especially for web and mobile clients.
Best practices
- Design clear, versioned APIs (e.g., v1, v2) to avoid breaking clients.
- Use consistent naming and HTTP status codes for REST APIs.
- Document APIs with OpenAPI or WSDL so clients can auto-generate code.
- Protect endpoints with TLS and proper authentication/authorization.
- Keep payloads compact and use pagination for large result sets.
Quick summary
Web services are the networked interfaces that let disparate systems talk to each other using standardized formats and protocols. Whether SOAP or REST, web services enable integration, automation, and the distributed applications that power modern software ecosystems.