SOAP – simple object access protocol

SOAP is a standard protocol that was first designed so that applications built with different languages and on different platforms could communicate. Because it is a protocol, it imposes built-in rules that increase its complexity and overhead, which can lead to longer page load times.

Common web service specifications include:

• Web services security (WS-security): Standardizes how messages are secured and transferred through unique identifiers called tokens.
• WS-ReliableMessaging: Standardizes error handling between messages transferred across unreliable IT infrastructure.
• Web services addressing (WS-addressing): Packages routing information as metadata within SOAP headers, instead of maintaining such information deeper within the network.
• Web services description language (WSDL): Describes what a web service does, and where that service begins and ends.

REST – representational state transfer

REST is a set of architectural principles attuned to the needs of lightweight web services and mobile applications.

When a request for data is sent to a REST API, it’s usually done through hypertext transfer protocol (commonly referred to as HTTP). Once a request is received, APIs designed for REST (called RESTful APIs or RESTful web services) can return messages in a variety of formats: HTML, XML, plain text, and JSON. JSON (JavaScript object notation) is favored as a message format because it can be read by any programming language (despite the name), is human- and machine-readable, and is lightweight. In this way, RESTful APIs are more flexible and can be easier to set up.