Definition: An Application Programming Interface (API) is a defined set of rules that allows different software applications, services, or systems to exchange data and request functionality from one another. An API specifies what requests can be made, what information must be provided, and how the receiving system will respond.
Why It Matters: APIs allow organizations to connect systems without rebuilding their underlying software. They support integrations such as displaying inventory from an e-commerce platform, sending form submissions to a CRM, processing online payments, retrieving analytics data, or connecting an artificial intelligence assistant to business applications.
How It Works: An application sends a structured request to an API endpoint. The receiving system authenticates the request, performs the permitted action, and returns a structured response, commonly using JSON. APIs may require credentials such as API keys, access tokens, or OAuth authorization to control access.
Common Types:
- REST APIs: Web-based APIs that commonly use standard HTTP methods such as GET, POST, PUT, and DELETE.
- GraphQL APIs: APIs that allow clients to request specific fields and related data through a flexible query language.
- Webhooks: Event-driven notifications sent automatically when a specified action occurs.
- Internal APIs: Interfaces used privately within an organization to connect internal systems.
Common Mistakes:
- Exposing API credentials in public code or browser scripts
- Providing excessive permissions instead of limiting access
- Failing to validate, monitor, or rate-limit requests
- Assuming an API automatically guarantees compatibility or data quality
Related: Model Context Protocol (MCP), REST API, GraphQL, Webhook, OAuth, API Key, System Integration