Application programming interface

An application programming interface, or API, is a defined interface through which software components interact using documented operations, inputs, outputs, and rules.

An API creates a boundary between an implementation and its callers. The useful engineering concern is the contract that callers can depend on.

APIs can be local library interfaces, network services, operating-system interfaces, or other software boundaries.

Related knowledge

API contracts and compatibilityDefine the promise an API makes to its clients, and change it without breaking the code that already depends on it.

Resource and operation designDecide what an API exposes as things and what it exposes as actions, and give each operation clear and predictable semantics.