API Key

An API key is a unique identifier issued to a developer or application that grants access to an API. It functions like a password - the API server checks the key on every request to verify the caller is authorized before returning data.

API keys are typically passed in HTTP request headers. On RapidAPI, the standard header is X-RapidAPI-Key. Keys should be stored securely in environment variables rather than hardcoded in source code, since an exposed key lets others consume your quota.

Most API platforms let you regenerate a key if it is compromised, and some support multiple keys for different applications or environments - for example, a separate key for development and production.