Web API

A web API is an application programming interface (API) for either a web server or a web browser. It can refer to a client-side JavaScript API (including any web frameworks being used) or a server-side web API. The latter consists of one or more endpoints to a defined request–response message system, typically expressed in JSON or XML by means of an HTTP-based web server.

A server API (SAPI) is not considered a server-side web API, unless it is publicly accessible by a remote web application.