# API Key

A secret string that identifies the calling program.

## What is **API Key**?

An **API key** is a secret string that identifies the calling program. It is sent in a header on every request. Keep it out of code and browsers.

```bash
curl https://api.weather.example.com/today -H "X-Api-Key: <your key>"
```

Level: Journeyman · [More REST API terms at this level](https://www.ask-codey.com/glossary/subjects/rest-api/journeyman)

Updated: September 27, 2026

Source: https://www.ask-codey.com/glossary/api-key