> ## 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.

# Introduction

> The fastest, most human-like Text-to-Speech API, built for real-time dialogue.

Nineninesix is a Text-to-Speech API built for **real-time dialogue** — the fastest, most human-like speech synthesis for voice agents, phone systems, and live conversational apps. Point your client at `https://api.nineninesix.ai` and start streaming natural speech in a single request.

## Why Nineninesix?

* **Fastest**: Ultra-low-latency streaming for sub-second time-to-first-audio, so conversations feel instant
* **Most human-like**: Dialogue-native voices trained on real conversational speech — natural prosody, pacing, and emotion, not flat long-form narration
* **Real-time by design**: Batch (`/tts/bytes`), Server-Sent Events (`/tts/sse`), and low-latency WebSocket (`/tts/websocket`) streaming
* **Simple billing**: 1 credit per character, \$5 per 1M characters, credits never expire

## Quick 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 world! This is Nineninesix.",
    "voice": { "mode": "id", "id": "<voice-id>" },
    "output_format": { "container": "wav", "encoding": "pcm_s16le", "sample_rate": 22050 }
  }' --output speech.wav
```

## Next Steps

<CardGroup cols={2}>
  <Card title="Quickstart" icon="rocket" href="/quickstart">
    Get up and running in under 5 minutes
  </Card>

  <Card title="Authentication" icon="key" href="/authentication">
    Learn how to authenticate API requests
  </Card>

  <Card title="API Reference" icon="code" href="/api-reference/speech">
    Full API documentation
  </Card>

  <Card title="SDKs" icon="box" href="/sdks">
    Drop-in SDK setup for your stack
  </Card>
</CardGroup>