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

# Choosing an API

> Pick between the REST, HTTP streaming, and WebSocket text-to-speech APIs.

Chariot offers three ways to synthesize speech. They produce the same audio from the same voices. The difference is **latency** and **how you deliver text**.

## Decision guide

<CardGroup cols={3}>
  <Card title="REST (sync)" icon="file-audio">
    You have short, complete text and want one finished WAV file. Simplest to integrate.
  </Card>

  <Card title="HTTP streaming" icon="wave-pulse">
    You have one complete utterance but want playback to start as early as possible.
  </Card>

  <Card title="WebSocket" icon="bolt">
    Text arrives incrementally (e.g. from an LLM), or you need a long, low-latency, interactive session.
  </Card>
</CardGroup>

## Comparison

|                    | REST `POST /v1/tts`   | HTTP stream `POST /v1/tts/stream` | WebSocket `/v1/tts/ws`                   |
| ------------------ | --------------------- | --------------------------------- | ---------------------------------------- |
| Connection         | One request/response  | One request, streamed response    | Persistent, bidirectional                |
| Time to first byte | After full synthesis  | Low (as generated)                | Low (per sentence)                       |
| Text delivery      | All at once           | All at once                       | Incremental, across messages             |
| Output             | WAV file              | Raw PCM (`audio/L16`)             | PCM or streaming-WAV frames per sentence |
| Max input          | 500 characters        | 500 characters                    | Unbounded across the session             |
| Billing            | Up front, per request | Up front, refunded on failure     | Per sentence, as generated               |
| Auth               | API key (header)      | API key (header)                  | API key (header or `?api_key=`)          |
| Best for           | Simplicity, batch     | Single low-latency utterance      | Real-time and long-form                  |

## Rules of thumb

* **Start with REST.** If you're generating short clips and don't need sub-second first audio, `POST /v1/tts` is the least code.
* **Reach for HTTP streaming** when you already have the full sentence but want the user to hear audio sooner, for example reading a chat reply aloud.
* **Use the WebSocket** when text is produced token-by-token (streaming from an LLM), when you're driving a voice agent, or when a single utterance would exceed 500 characters. You send `input.text` messages as text becomes available and receive audio per sentence. See [WebSocket streaming](/guides/text-to-speech/websocket).

<Note>
  Concurrency limits are enforced per plan on the synchronous `POST /v1/tts` endpoint. If you need many simultaneous generations, see [Rate limits & concurrency](/guides/resources/rate-limits) before choosing a transport.
</Note>