Microservice is often referred to as a remotely callable API, but it is much more than the older network-callable API or remote process execution standards such as Remote Method Invocation (RMI), Common Object Request Broker Architecture (CORBA), or Distributed Component Object Model (DCOM) - callable API standards.

Web API is, however, most common in the Microsoft world, where Web APIs (server-side) are REST-based services that use HTTP verbs to define actions on the business resources (data). This kind of service typically uses JSON or XML (or sometimes in binary) as the request and response format.

Web services are services which are traditionally SOAP (simple object access protocol) based services whose request and responses are in XML, or sometimes, in binary. A web service is typically exposed by a standard WSDL (web services description language) as an interface definition language, which is used to create the proxies at the web service caller end.