Application programming interface (API)

An application programming interface (API) is a defined interface that lets one software application exchange data with, or request functions from, another application or service. It commonly refers to the rules, endpoints, data formats, authentication methods, and expected responses that make system-to-system communication possible.

An API is not the same thing as a user interface. People interact with screens, forms, and buttons, while software interacts with APIs. An API is also not the entire integration by itself. In practice, the full integration may also include data mapping, transformation logic, error handling, monitoring, and security controls.

How it is used in manufacturing and regulated operations

In manufacturing environments, APIs are commonly used to connect business and operational systems such as ERP, MES, QMS, PLM, CMMS, LIMS, and warehouse or supplier platforms. They allow systems to pass structured information without relying on manual re-entry.

• An ERP sends production orders to an MES through an API.
• An MES posts production results, material consumption, or lot data back to an ERP.
• A QMS receives nonconformance or inspection data from an execution system.
• A document or training system checks status information from another platform through an API.

Depending on the design, an API may support real-time exchange, near-real-time updates, or event-driven communication. Some APIs are internal to one organization, while others are exposed for suppliers, customers, or third-party software.

What an API typically includes

• Defined requests and responses
• Data structures or schemas
• Authentication and authorization methods
• Error codes and status handling
• Versioning rules
• Documentation for developers or integrators

Common implementation styles include REST APIs, SOAP APIs, GraphQL APIs, and event or message-based interfaces. In industrial settings, APIs may also be used alongside protocols and standards that are more specific to equipment or OT environments.

Common confusion

API vs integration: An API is a mechanism that can enable integration, but an integration usually includes broader workflow and data-handling logic.

API vs EDI: EDI is a structured document exchange approach often used in supply chains. APIs are generally more flexible and interactive, but they serve a different technical pattern.

API vs protocol: A protocol defines communication rules at a technical level. An API defines how software should request or exchange specific application data or functions. The two can overlap, but they are not identical.

API vs connector: A connector is usually a packaged integration component built on top of one or more APIs.

Boundary notes

In some contexts, API can also refer more broadly to a software library interface used by developers inside the same application environment. In enterprise and manufacturing systems, however, it most often means a web or service interface used to connect separate systems.