Application programming interface (API)

An application programming interface (API) is a defined way for software systems to exchange requests and data.

Format
Web & Development
Updated
Updated
Glossary Web & Development
Application programming interface Also known as API.Aliases: web API.

Definition

An application programming interface (API) is a defined way for software systems to exchange requests and data.

How it works

An API spells out what a system can be asked to do: the operations available, the inputs they expect, and the shape of the answers. On the web that usually means requests over HTTP with JSON going back and forth. It is what lets one service work with another without either needing to see the other's internal wiring.

Example: A billing dashboard might call an API to pull up a customer's active services.

Often confused: An API is the contract between two pieces of software; a user interface is the screen a person clicks on.

Sources

Last reviewed 2026-07-19.