> ## Documentation Index
> Fetch the complete documentation index at: https://nango.dev/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Authentication

Use an [API key](/reference/backend/http-api/api-keys) as a Bearer token in the `Authorization` header. API keys are managed in **Environment Settings > API Keys** in the Nango UI.

```
Authorization: Bearer <NANGO-API-KEY>
```

Each API key has [scopes](/reference/backend/http-api/api-keys#scopes) that control which endpoints it can access. A key without the required scope will receive a `403 Forbidden` response.