---
title: Text to Speech
product: vercel
url: /docs/ai-gateway/modalities/text-to-speech
canonical_url: "https://vercel.com/docs/ai-gateway/modalities/text-to-speech"
last_updated: 2018-10-20
type: conceptual
prerequisites:
  - /docs/ai-gateway/modalities
  - /docs/ai-gateway
related:
  - /docs/ai-gateway/modalities/realtime
  - /docs/ai-gateway/modalities/speech-to-text
summary: Learn about text to speech on Vercel.
install_vercel_plugin: npx plugins add vercel/vercel-plugin
---

# Text to Speech

Generate spoken audio from text with speech models such as `openai/tts-1` and `openai/gpt-4o-mini-tts`. Use this for voiceovers, audio versions of written content, or spoken responses in your app.

Use this to turn text into spoken audio. For live, two-way voice, see [Realtime](/docs/ai-gateway/modalities/realtime); to transcribe recorded audio, see [Speech to Text](/docs/ai-gateway/modalities/speech-to-text).

> **💡 Note:** Text to speech is in beta and access is rolling out gradually. Speech models
> may not appear in the model catalog yet for your team.

## Generate speech with the AI SDK

Use `experimental_generateSpeech` with a speech model from the AI Gateway provider:

```typescript filename="generate-speech.ts"
import { experimental_generateSpeech as generateSpeech } from 'ai';
import { gateway } from '@ai-sdk/gateway';
import { writeFile } from 'node:fs/promises';

const result = await generateSpeech({
  model: gateway.speechModel('openai/tts-1'),
  text: 'Hello! Thanks for trying out AI Gateway.',
  voice: 'alloy',
  outputFormat: 'mp3',
});

await writeFile('greeting.mp3', result.audio.uint8Array);
```

> **💡 Note:** Speech support in the AI Gateway provider is available on the canary releases
> of the AI SDK. Install them with `pnpm add ai@canary @ai-sdk/gateway@canary`.

### Request options

| Option         | Description                                                              |
| -------------- | ------------------------------------------------------------------------ |
| `text`         | The text to convert to speech. Required.                                 |
| `voice`        | The voice to use, such as `alloy`. Available voices depend on the model. |
| `outputFormat` | The audio format, such as `mp3` or `wav`.                                |
| `instructions` | Directions for how the model should speak, such as tone or pacing.      |
| `speed`        | Playback speed. Defaults to 1.                                           |
| `language`     | The language of the input text.                                          |

Support for each option varies by model. Unsupported options are reported in `warnings` on the result instead of failing the request.

## Generate speech with the REST API

You can also call the speech endpoint directly. Send a `POST` request with the model in the `ai-model-id` header. The response contains the audio as a base64-encoded string:

#### cURL

```bash filename="generate-speech.sh"
curl -X POST https://ai-gateway.vercel.sh/v4/ai/speech-model \
  -H "Authorization: Bearer $AI_GATEWAY_API_KEY" \
  -H "ai-model-id: openai/tts-1" \
  -H "Content-Type: application/json" \
  -d '{
    "text": "Hello! Thanks for trying out AI Gateway.",
    "voice": "alloy",
    "outputFormat": "mp3"
  }' | jq -r '.audio' | base64 -d > greeting.mp3
```

#### TypeScript

```typescript filename="generate-speech-rest.ts"
import { writeFile } from 'node:fs/promises';

const response = await fetch(
  'https://ai-gateway.vercel.sh/v4/ai/speech-model',
  {
    method: 'POST',
    headers: {
      Authorization: `Bearer ${process.env.AI_GATEWAY_API_KEY}`,
      'ai-model-id': 'openai/tts-1',
      'Content-Type': 'application/json',
    },
    body: JSON.stringify({
      text: 'Hello! Thanks for trying out AI Gateway.',
      voice: 'alloy',
      outputFormat: 'mp3',
    }),
  },
);

const result = await response.json();
await writeFile('greeting.mp3', Buffer.from(result.audio, 'base64'));
```

The response is a JSON object with the base64-encoded audio:

```json filename="response.json"
{
  "audio": "SUQzBAAAAAAA...",
  "warnings": []
}
```

## Limitations

- Audio returns base64-encoded in a JSON response. Streaming audio output is not supported.
- Text to speech supports OpenAI speech models only.


---

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