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

# API Key Overview

> Authenticate API requests and secure webhooks using API keys.

API keys are used to authenticate your requests to:

* REST API endpoints
* SDK integrations
* Webhook endpoints

Each workspace can have multiple API keys, all sharing the same permission level.

### REST API Authentication

To authenticate your REST API requests, include your API key in the request headers:

```http theme={null}
Authorization: Bearer YOUR_API_KEY
```

Try out authentication in our [API Playground](/api-references/create-phone-call) to see it in action.

### Webhook API Key

For enhanced security, we automatically designate one of your API keys for [webhook authentication](/features/secure-webhook). This designated webhook API key:

* Is used to sign and verify webhook requests
* Cannot be deleted
* Ensures your webhook endpoints only receive legitimate requests

<Note>
  Keep your API keys secure and never share them in public repositories or client-side code.
</Note>