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

# Authentication

> How to authenticate with the FHIR API

## Authentication

The **Ferrum** supports various authentication mechanisms depending on your deployment configuration.

## Bearer Token Authentication

Most deployments use Bearer token authentication. Include the token in the `Authorization` header:

```bash theme={null}
curl -H "Authorization: Bearer YOUR_TOKEN" \
     https://your-server.com/fhir/Patient/123
```

## API Key Authentication

Some deployments may use API keys. Include the key in a custom header:

```bash theme={null}
curl -H "X-API-Key: YOUR_API_KEY" \
     https://your-server.com/fhir/Patient/123
```

## OAuth 2.0

For OAuth 2.0 authentication, follow the standard OAuth 2.0 flow:

1. Obtain an access token from your authorization server
2. Include the token in the `Authorization` header as a Bearer token

```bash theme={null}
curl -H "Authorization: Bearer ACCESS_TOKEN" \
     https://your-server.com/fhir/Patient/123
```

## Unauthenticated Access

Some endpoints may be configured for public access (read-only). Check your server configuration for details.

<Warning>
  Always use HTTPS in production to protect authentication credentials.
</Warning>