Application programming interface

set of subroutine definitions, protocols, and tools for building software and applications

An Application Programming Interface (API) is a set of functions, procedures, methods or classes used by computer programs to request services from the operating system, software libraries or any other service providers running on the computer. A computer programmer uses the API to make application programs.

An API works by communicating with and exchanging data with other systems, acting as a messenger between the user and the system to retrieve the necessary data the user is requesting from the system.

Main types of web APIs:

  • Open APIs - available to the public; they can be accessed by any external users.
  • Partner APIs - available to strategic business partners; they are exposed to a public API developer portal.
  • Internal APIs - available to a company's internal development teams; they are exposed to a private API developer portal.
  • Composite APIs - are a sequence of tasks bundled into a single API call.[1]

Types of API include web services API like the Twitter API, which allows programs to use the API to receive updates on tweets.


  1. "Types of APIs | Learn about the Different Types of APIs in 2020". API Friends. 2020-04-29. Retrieved 2020-04-30.