REST vs SOAP: Understanding the Key Differences

This article explores the main differences between REST and SOAP. Comparing the two is like comparing apples and oranges, as SOAP is a protocol format based on XML, while REST is an architectural style.

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REST vs SOAP: Understanding the Key Differences

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REST and SOAP are not comparable. REST is a software architectural style, while SOAP is a message exchange format. Let's compare the implementations of the popular REST and SOAP styles:

  • RESTful implementation example: RESTful is based on the HTTP protocol and can use JSON as the data format to transmit RESTful API.
  • SOAP implementation example: SOAP is a simple protocol based on XML that allows applications to exchange information over HTTP.

At the top level, SOAP restricts the structure of messages, while REST is an architectural approach that focuses on using HTTP as the transport protocol.

  • SOAP is special in that it is a data exchange format. For SOAP, it is always SOAP-XML, that is, XML, which contains the following elements:

Required SOAP envelope - the root element that defines the message and name space used in the document.

Optional SOAP header - contains message properties such as security information or network routing.

Required SOAP body - contains the message exchanged between applications.

Optional Fault element - provides information about errors that occurred while processing this message. Requests and responses must comply with the SOAP structure.

REST is special in that it uses HTTP as the transport protocol. This means taking full advantage of the features provided by HTTP - request methods, headers, responses, response headers, etc.

Message Format

  • In SOAP, requests and responses must be in SOAP XML format.
  • In REST, there is no fixed format. We can exchange messages based on XML, JSON, or any other format. JSON is the most popular format.

Service Definition

  • SOAP uses WSDL (Web Service Description Language), which is an XML-based language used to describe and access web services.
  • REST does not have a standard service definition language. Although WADL was one of the earliest proposed standards, it is not very popular. Swagger or Open API are currently more widely used and accepted.


SOAP does not impose any restrictions on the type of transport protocol used. We can use HTTP web protocol or MQ, while REST is best used with the HTTP transport protocol.

Usability RESTful web services are usually easier to implement than SOAP-based web services.

  • REST usually uses JSON, which is easier to parse and process. In addition, REST does not require a service definition to provide web services.
  • In addition to requiring WSDL to define services, SOAP also requires effort to process and parse SOAP-XML messages.