Side by side
REST APIvsSOAP
What is the difference between REST and SOAP?
Updated 2 min read7 differences
In short
REST is a lightweight API style on plain HTTP, URLs and usually JSON, while SOAP is a formal protocol that wraps messages in XML under a strict WSDL contract.
REST API
Representational State Transfer API
A REST API is a web API that exposes data as resources identified by URLs and lets clients read or change them using standard HTTP methods.
Read the page on REST APISOAP
Simple Object Access Protocol
SOAP is an XML-based messaging protocol for web services that wraps each request and response in a strict envelope, usually defined by a formal WSDL contract.
Read the page on SOAPREST API and SOAP compared
| Aspect | REST API | SOAP |
|---|---|---|
| What it is | An architectural style | A protocol with a formal specification |
| Message format | Usually JSON, but also XML or others | Always XML inside a SOAP envelope |
| Contract | Optional, often written in OpenAPI | A WSDL file, usually required |
| Transport | HTTP | Mostly HTTP, but also SMTP, JMS and others |
| Caching | Standard HTTP caching for GET requests | Hardly any; requests are usually POST |
| Security | HTTPS plus tokens such as OAuth | WS-Security standards for signing and encrypting each message |
| Best for | Web and mobile apps, public APIs | Enterprise integrations with strict contracts |
The difference, explained
SOAP, originally short for Simple Object Access Protocol, appeared around 2000 for exchanging messages between systems and became a W3C standard in 2003. Every request and response is an XML document with an envelope, an optional header and a body, and a WSDL file describes the operations a service offers. REST, described by Roy Fielding the same year, is not a protocol but an architectural style: resources have URLs and are handled with HTTP methods such as GET, PUT and DELETE.
The key difference is weight and strictness. SOAP specifies a lot: the message format, the error format, and extension standards for security (WS-Security), transactions and reliable delivery, and it can travel over transports other than HTTP. REST leans on what HTTP already provides, such as status codes, caching and authentication headers, which keeps calls short and easy to try from a browser or curl.
Today REST, along with GraphQL and gRPC, is the default for new public and mobile APIs. SOAP remains common in banking, insurance, healthcare, government and older enterprise systems, where its formal contracts and security standards were adopted long ago, so many developers still have to call SOAP services from REST-based applications.
A common misconception is that SOAP is simply old and REST simply better. SOAP's strict contracts, generated clients and standard security are real advantages in some integrations, while REST's freedom means every API invents its own conventions for errors, versioning and documentation, often filled in with OpenAPI.
Which one should you use?
Choose REST API when…
- You are building a new web, mobile or public API.
- You want small JSON messages and HTTP caching.
- Developers should be able to explore the API with plain HTTP tools.
Choose SOAP when…
- You integrate with an existing system that only offers SOAP.
- You need message-level security or standards for reliable delivery.
- Both sides want a strict, machine-readable contract to generate code from.
Asking for one user
GET /users/42 HTTP/1.1
Host: api.example.com
Accept: application/json
HTTP/1.1 200 OK
Content-Type: application/json
{ "id": 42, "name": "Ada" }POST /UserService HTTP/1.1
Host: api.example.com
Content-Type: text/xml; charset=utf-8
SOAPAction: "GetUser"
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Body>
<GetUser xmlns="http://example.com/users">
<Id>42</Id>
</GetUser>
</soap:Body>
</soap:Envelope>Readers ask
Is SOAP still used?
Yes, mostly in banking, insurance, healthcare, telecoms and government systems, and in older enterprise software. Most new APIs use REST, GraphQL or gRPC instead.
Can REST use XML?
Yes. REST does not fix a data format, and JSON is simply the most common choice. A REST API can return XML, CSV or anything else a client asks for with the Accept header.
Is SOAP more secure than REST?
Not automatically. SOAP has standards for signing and encrypting individual messages, which some industries require, but a REST API served over HTTPS with proper authentication is secure for most uses.