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

# Authentication

> Learn how to authenticate your requests to the Nineninesix API.

All API requests require an API key. Keys are scoped to a **project** within your organization.

## API Keys

API keys follow the format `sk_996_<prefix>_<secret>` and are created from your [dashboard](https://nineninesix.ai/api-keys).

<Warning>
  API keys are shown only once at creation. Store them securely — we only keep a
  hash on our end.
</Warning>

## Using Your Key

Pass the key as a Bearer token (or in the `X-API-Key` header):

```bash theme={null}
Authorization: Bearer sk_996_your_api_key
```

For WebSocket connections that can't set headers, pass the key as a query parameter: `?api_key=sk_996_...`.

### Full Example

```bash theme={null}
curl -N https://api.nineninesix.ai/tts/bytes \
  -H "Authorization: Bearer sk_996_your_api_key" \
  -H "Content-Type: application/json" \
  -d '{"model_id":"gepard-1.0","transcript":"Hello!","voice":{"mode":"id","id":"<voice-id>"},"output_format":{"container": "wav", "encoding": "pcm_s16le", "sample_rate": 22050}}'
```

### With an SDK

<CodeGroup>
  ```python Python theme={null}
  from cartesia import Cartesia

  client = Cartesia(
      api_key="sk_996_your_api_key",
      base_url="https://api.nineninesix.ai",
  )
  ```

  ```typescript Node.js theme={null}
  import { Cartesia } from "@cartesia/cartesia-js";

  const client = new Cartesia({
    apiKey: "sk_996_your_api_key",
    baseURL: "https://api.nineninesix.ai",
  });
  ```
</CodeGroup>

## Security Best Practices

* **Never expose keys in client-side code** — always call the API from your server
* **Use environment variables** to store keys (e.g. `NINENINESIX_API_KEY`)
* **Rotate keys regularly** — revoke old keys and generate new ones from the dashboard
* **Use separate keys** for development and production

## Key Management

You can manage your API keys from the [API Keys page](https://nineninesix.ai/api-keys):

* **Create** — generate a new key with a descriptive name
* **Revoke** — immediately disable a key (cannot be undone)
* **Monitor** — see when each key was last used