GLOSSARY
API (AI API)
The programming interface that lets developers call an AI model from their own software, usually billed per use.
An API (application programming interface) is how software talks to software. AI APIs let developers send a prompt to a model and receive the result programmatically — the ChatGPT app is a front end for OpenAI's API, and thousands of products are front ends for someone's models.
Most tools in this directory offer APIs (filter by 'API' in our collections), typically priced per token or per second of compute. Choosing between building on an API, self-hosting open weights, or simply using a finished app is the first architecture decision every AI product team makes.