Application programming interface (API)
An application programming interface (API) is a defined way for one piece of software to communicate with another. It specifies what requests the software can make, what information each request must include, and what kind of response it will receive.
For example, an accounting system might provide an API that allows another application to create an invoice. The application sends the invoice details in the format the API expects, and the accounting system responds with the result. The application does not need to know how the accounting system performs its work internally.
APIs can connect software made by different vendors or separate parts of the same application.
Why are APIs useful?
For a small or midsize business, APIs can make it possible to:
- connect systems without repeatedly entering the same information;
- automate routine work;
- add capabilities such as payments, shipping, maps, or AI;
- build custom workflows around commercial software; and
- replace one component without rebuilding an entire system.
Having an API does not guarantee that an integration will be simple. Vendors decide which capabilities their APIs expose, and they may impose fees, usage limits, or technical restrictions. An integration also needs to handle security, service outages, and changes to the API over time.
Before selecting business software, it is worth considering not only what the product does today, but also whether its API will allow it to work with other systems the business may need later.