---
title: Gemini 3.1 Flash TTS | Runware Docs
url: https://runware.ai/docs/models/google-gemini-3-1-flash-tts
description: Expressive text-to-speech with audio tags, multi-speaker dialogue, and 70+ languages
---
# Gemini 3.1 Flash TTS

Gemini 3.1 Flash TTS is a text-to-speech model for expressive spoken audio generation from text. It supports granular control over delivery through audio tags, native multi-speaker dialogue, and speech generation across 70+ languages, making it suitable for narration, conversational voice apps, podcasts, audiobooks, and other production-oriented voice workflows.

- **ID**: `google:gemini@3.1-flash-tts`
- **Status**: coming-soon
- **Creator**: Google
- **Release Date**: April 15, 2026
- **Capabilities**: Text to Audio

## Pricing

- **Input tokens**: `$1 / 1M`
- **Audio output tokens**: `$20 / 1M`

## Compatibility & Validation

`voice` cannot be used with `voices` (in `speech`).

## Request Parameters

**API Options**

Platform-level options for task execution and delivery.

### [taskType](https://runware.ai/docs/models/google-gemini-3-1-flash-tts#request-tasktype)

- **Type**: `string`
- **Required**: true
- **Value**: `audioInference`

Identifier for the type of task being performed

### [taskUUID](https://runware.ai/docs/models/google-gemini-3-1-flash-tts#request-taskuuid)

- **Type**: `string`
- **Required**: true
- **Format**: `UUID v4`

UUID v4 identifier for tracking tasks and matching async responses. Must be unique per task.

### [outputType](https://runware.ai/docs/models/google-gemini-3-1-flash-tts#request-outputtype)

- **Type**: `string`
- **Default**: `URL`

Audio output type.

**Allowed values**: `URL` `base64Data` `dataURI`

### [outputFormat](https://runware.ai/docs/models/google-gemini-3-1-flash-tts#request-outputformat)

- **Type**: `string`
- **Default**: `MP3`

Specifies the file format of the generated output. The available values depend on the task type and the specific model's capabilities.

- \`MP3\`: Compressed audio, smaller file size.
- \`WAV\`: Uncompressed, high-quality audio.
- \`FLAC\`: Lossless compression.
- \`OGG\`: Open-source compressed audio format (Vorbis codec).

**Allowed values**: `MP3` `WAV` `FLAC` `OGG`

### [audioSettings](https://runware.ai/docs/models/google-gemini-3-1-flash-tts#request-audiosettings)

- **Path**: `audioSettings.bitrate`
- **Type**: `object (3 properties)`

Audio encoding settings for controlling the bitrate, number of channels, and sample rate of the generated audio. Only applicable for lossy output formats (`MP3` and `OGG`). When using lossless formats (`WAV` or `FLAC`), this parameter must not be provided.

The available sample rates and valid bitrate ranges depend on the output format. For `OGG`, bitrate limits also vary by the number of channels.

**MP3 bitrate limits**:

Bitrate limits for MP3 are the same regardless of mono or stereo.

| Sample Rate | Min Bitrate | Max Bitrate |
| --- | --- | --- |
| 8,000 Hz | 8 kbps | 64 kbps |
| 11,025 Hz | 8 kbps | 64 kbps |
| 12,000 Hz | 8 kbps | 64 kbps |
| 16,000 Hz | 8 kbps | 160 kbps |
| 22,050 Hz | 8 kbps | 160 kbps |
| 24,000 Hz | 8 kbps | 160 kbps |
| 32,000 Hz | 32 kbps | 320 kbps |
| 44,100 Hz | 32 kbps | 320 kbps |
| 48,000 Hz | 32 kbps | 320 kbps |

**OGG bitrate limits — Mono (1 channel)**:

| Sample Rate | Min Bitrate | Max Bitrate |
| --- | --- | --- |
| 8,000 Hz | 8 kbps | 40 kbps |
| 12,000 Hz | 16 kbps | 48 kbps |
| 16,000 Hz | 16 kbps | 96 kbps |
| 24,000 Hz | 16 kbps | 80 kbps |
| 48,000 Hz | 32 kbps | 224 kbps |

**OGG bitrate limits — Stereo (2 channels)**:

| Sample Rate | Min Bitrate | Max Bitrate |
| --- | --- | --- |
| 8,000 Hz | 16 kbps | 80 kbps |
| 12,000 Hz | 16 kbps | 96 kbps |
| 16,000 Hz | 24 kbps | 192 kbps |
| 24,000 Hz | 32 kbps | 160 kbps |
| 48,000 Hz | 48 kbps | 256 kbps |

> [!NOTE]
> **Lossless formats**: When `outputFormat` is set to `WAV` or `FLAC`, the `audioSettings` parameter is not available since these formats produce uncompressed or lossless audio with no configurable encoding settings.

#### [bitrate](https://runware.ai/docs/models/google-gemini-3-1-flash-tts#request-audiosettings-bitrate)

- **Path**: `audioSettings.bitrate`
- **Type**: `integer`
- **Min**: `8`

Audio bitrate in kbps.

#### [channels](https://runware.ai/docs/models/google-gemini-3-1-flash-tts#request-audiosettings-channels)

- **Path**: `audioSettings.channels`
- **Type**: `integer`
- **Default**: `2`

Number of audio channels. 1 for mono, 2 for stereo.

**Allowed values**: `1` `2`

#### [sampleRate](https://runware.ai/docs/models/google-gemini-3-1-flash-tts#request-audiosettings-samplerate)

- **Path**: `audioSettings.sampleRate`
- **Type**: `integer`

Audio sample rate in Hz.

### [webhookURL](https://runware.ai/docs/models/google-gemini-3-1-flash-tts#request-webhookurl)

- **Type**: `string`
- **Format**: `URI`

Specifies a webhook URL where JSON responses will be sent via HTTP POST when generation tasks complete. For batch requests with multiple results, each completed item triggers a separate webhook call as it becomes available.

**Learn more** (1 resource):

- [Webhooks](https://runware.ai/docs/platform/webhooks) (platform)

### [deliveryMethod](https://runware.ai/docs/models/google-gemini-3-1-flash-tts#request-deliverymethod)

- **Type**: `string`
- **Default**: `sync`

Determines how the API delivers task results.

**Allowed values**:

- `sync` Returns complete results directly in the API response.
- `async` Returns an immediate acknowledgment with the task UUID. Poll for results using getResponse.

**Learn more** (1 resource):

- [Task Polling](https://runware.ai/docs/platform/task-polling) (platform)

### [uploadEndpoint](https://runware.ai/docs/models/google-gemini-3-1-flash-tts#request-uploadendpoint)

- **Type**: `string`
- **Format**: `URI`

Specifies a URL where the generated content will be automatically uploaded using the HTTP PUT method. The raw binary data of the media file is sent directly as the request body. For secure uploads to cloud storage, use presigned URLs that include temporary authentication credentials.

**Common use cases:**

- **Cloud storage**: Upload directly to S3 buckets, Google Cloud Storage, or Azure Blob Storage using presigned URLs.
- **CDN integration**: Upload to content delivery networks for immediate distribution.

```text
// S3 presigned URL for secure upload
https://your-bucket.s3.amazonaws.com/generated/content.mp4?X-Amz-Signature=abc123&X-Amz-Expires=3600

// Google Cloud Storage presigned URL
https://storage.googleapis.com/your-bucket/content.jpg?X-Goog-Signature=xyz789

// Custom storage endpoint
https://storage.example.com/uploads/generated-image.jpg
```

The content data will be sent as the request body to the specified URL when generation is complete.

### [ttl](https://runware.ai/docs/models/google-gemini-3-1-flash-tts#request-ttl)

- **Type**: `integer`
- **Min**: `60`

Time-to-live (TTL) in seconds for generated content. Only applies when `outputType` is `URL`.

### [includeCost](https://runware.ai/docs/models/google-gemini-3-1-flash-tts#request-includecost)

- **Type**: `boolean`
- **Default**: `false`

Include task cost in the response.

### [numberResults](https://runware.ai/docs/models/google-gemini-3-1-flash-tts#request-numberresults)

- **Type**: `integer`
- **Min**: `1`
- **Max**: `4`
- **Default**: `1`

Number of results to generate. Each result uses a different seed, producing variations of the same parameters.

**Generation Parameters**

Core parameters for controlling the generated content.

### [model](https://runware.ai/docs/models/google-gemini-3-1-flash-tts#request-model)

- **Type**: `string`
- **Required**: true
- **Value**: `google:gemini@3.1-flash-tts`

Identifier of the model to use for generation.

**Learn more** (3 resources):

- [Text To Image: Model Selection The Foundation Of Generation](https://runware.ai/docs/guides/text-to-image#model-selection-the-foundation-of-generation) (guide)
- [Image Inpainting: Model Specialized Inpainting Models](https://runware.ai/docs/guides/image-inpainting#model-specialized-inpainting-models) (guide)
- [Image Outpainting: Other Critical Parameters](https://runware.ai/docs/guides/image-outpainting#other-critical-parameters) (guide)

### [speech](https://runware.ai/docs/models/google-gemini-3-1-flash-tts#request-speech)

- **Path**: `speech.text`
- **Type**: `object (6 properties)`
- **Required**: true

Settings for speech generation.

#### [text](https://runware.ai/docs/models/google-gemini-3-1-flash-tts#request-speech-text)

- **Path**: `speech.text`
- **Type**: `string`
- **Required**: true
- **Min**: `1`
- **Max**: `4000`

Text to convert to speech. For dialogue mode, use speaker tags such as \[Sam\] Hello \[Bob\] Hi there. Provider markup tags like \[laughs\] and \[short pause\] are also supported.

**Learn more** (2 resources):

- [Speech Generation: Prompting Guide](https://ai.google.dev/gemini-api/docs/speech-generation#prompting-guide) (external)
- [Speech Generation: Transcript Tags](https://ai.google.dev/gemini-api/docs/speech-generation#transcript-tags) (external)

#### [voice](https://runware.ai/docs/models/google-gemini-3-1-flash-tts#request-speech-voice)

- **Path**: `speech.voice`
- **Type**: `string`
- **Default**: `Zephyr`

Voice identifier to use. Set to `auto` for automatic selection.

**Allowed values**:

- `Achernar` Female, Soft
- `Achird` Male, Friendly
- `Algenib` Male, Gravelly
- `Algieba` Male, Smooth
- `Alnilam` Male, Firm
- `Aoede` Female, Breezy
- `Autonoe` Female, Bright
- `Callirrhoe` Female, Easy-going
- `Charon` Male, Informative
- `Despina` Female, Smooth
- `Enceladus` Male, Breathy
- `Erinome` Female, Clear
- `Fenrir` Male, Excitable
- `Gacrux` Female, Mature
- `Iapetus` Male, Clear
- `Kore` Female, Firm
- `Laomedeia` Female, Upbeat
- `Leda` Female, Youthful
- `Orus` Male, Firm
- `Puck` Male, Upbeat
- `Pulcherrima` Female, Forward
- `Rasalgethi` Male, Informative
- `Sadachbia` Male, Lively
- `Sadaltager` Male, Knowledgeable
- `Schedar` Male, Even
- `Sulafat` Female, Warm
- `Umbriel` Male, Easy-going
- `Vindemiatrix` Female, Gentle
- `Zephyr` Female, Bright
- `Zubenelgenubi` Male, Casual

#### [voices](https://runware.ai/docs/models/google-gemini-3-1-flash-tts#request-speech-voices)

- **Path**: `speech.voices`
- **Type**: `array of objects (2 properties)`

Two-speaker dialogue configuration. Use instead of voice for multi-speaker generation.

##### [speaker](https://runware.ai/docs/models/google-gemini-3-1-flash-tts#request-speech-voices-speaker)

- **Path**: `speech.voices.speaker`
- **Type**: `string`
- **Required**: true
- **Min**: `1`

Unique alphanumeric speaker alias. Must appear in the text as \[Alias\].

##### [voice](https://runware.ai/docs/models/google-gemini-3-1-flash-tts#request-speech-voices-voice)

- **Path**: `speech.voices.voice`
- **Type**: `string`
- **Required**: true
- **Default**: `Zephyr`

Voice identifier to use. Set to `auto` for automatic selection.

**Allowed values**:

- `Achernar` Female, Soft
- `Achird` Male, Friendly
- `Algenib` Male, Gravelly
- `Algieba` Male, Smooth
- `Alnilam` Male, Firm
- `Aoede` Female, Breezy
- `Autonoe` Female, Bright
- `Callirrhoe` Female, Easy-going
- `Charon` Male, Informative
- `Despina` Female, Smooth
- `Enceladus` Male, Breathy
- `Erinome` Female, Clear
- `Fenrir` Male, Excitable
- `Gacrux` Female, Mature
- `Iapetus` Male, Clear
- `Kore` Female, Firm
- `Laomedeia` Female, Upbeat
- `Leda` Female, Youthful
- `Orus` Male, Firm
- `Puck` Male, Upbeat
- `Pulcherrima` Female, Forward
- `Rasalgethi` Male, Informative
- `Sadachbia` Male, Lively
- `Sadaltager` Male, Knowledgeable
- `Schedar` Male, Even
- `Sulafat` Female, Warm
- `Umbriel` Male, Easy-going
- `Vindemiatrix` Female, Gentle
- `Zephyr` Female, Bright
- `Zubenelgenubi` Male, Casual

#### [language](https://runware.ai/docs/models/google-gemini-3-1-flash-tts#request-speech-language)

- **Path**: `speech.language`
- **Type**: `string`
- **Min**: `1`
- **Default**: `en-US`

Language code for speech generation.

**Allowed values**:

- `ar-EG` Arabic (Egypt)
- `bn-BD` Bangla (Bangladesh)
- `nl-NL` Dutch (Netherlands)
- `en-IN` English (India)
- `en-US` English (United States)
- `fr-FR` French (France)
- `de-DE` German (Germany)
- `hi-IN` Hindi (India)
- `id-ID` Indonesian (Indonesia)
- `it-IT` Italian (Italy)
- `ja-JP` Japanese (Japan)
- `ko-KR` Korean (South Korea)
- `mr-IN` Marathi (India)
- `pl-PL` Polish (Poland)
- `pt-BR` Portuguese (Brazil)
- `ro-RO` Romanian (Romania)
- `ru-RU` Russian (Russia)
- `es-ES` Spanish (Spain)
- `ta-IN` Tamil (India)
- `te-IN` Telugu (India)
- `th-TH` Thai (Thailand)
- `tr-TR` Turkish (Turkey)
- `uk-UA` Ukrainian (Ukraine)
- `vi-VN` Vietnamese (Vietnam)
- `af-ZA` Afrikaans (South Africa)
- `sq-AL` Albanian (Albania)
- `am-ET` Amharic (Ethiopia)
- `ar-001` Arabic (World)
- `hy-AM` Armenian (Armenia)
- `az-AZ` Azerbaijani (Azerbaijan)
- `eu-ES` Basque (Spain)
- `be-BY` Belarusian (Belarus)
- `bg-BG` Bulgarian (Bulgaria)
- `my-MM` Burmese (Myanmar)
- `ca-ES` Catalan (Spain)
- `ceb-PH` Cebuano (Philippines)
- `cmn-CN` Chinese, Mandarin (China)
- `cmn-tw` Chinese, Mandarin (Taiwan)
- `hr-HR` Croatian (Croatia)
- `cs-CZ` Czech (Czech Republic)
- `da-DK` Danish (Denmark)
- `en-AU` English (Australia)
- `en-GB` English (United Kingdom)
- `et-EE` Estonian (Estonia)
- `fil-PH` Filipino (Philippines)
- `fi-FI` Finnish (Finland)
- `fr-CA` French (Canada)
- `gl-ES` Galician (Spain)
- `ka-GE` Georgian (Georgia)
- `el-GR` Greek (Greece)
- `gu-IN` Gujarati (India)
- `ht-HT` Haitian Creole (Haiti)
- `he-IL` Hebrew (Israel)
- `hu-HU` Hungarian (Hungary)
- `is-IS` Icelandic (Iceland)
- `jv-JV` Javanese (Java)
- `kn-IN` Kannada (India)
- `kok-IN` Konkani (India)
- `lo-LA` Lao (Laos)
- `la-VA` Latin (Vatican City)
- `lv-LV` Latvian (Latvia)
- `lt-LT` Lithuanian (Lithuania)
- `lb-LU` Luxembourgish (Luxembourg)
- `mk-MK` Macedonian (North Macedonia)
- `mai-IN` Maithili (India)
- `mg-MG` Malagasy (Madagascar)
- `ms-MY` Malay (Malaysia)
- `ml-IN` Malayalam (India)
- `mn-MN` Mongolian (Mongolia)
- `ne-NP` Nepali (Nepal)
- `nb-NO` Norwegian, Bokmål (Norway)
- `nn-NO` Norwegian, Nynorsk (Norway)
- `or-IN` Odia (India)
- `ps-AF` Pashto (Afghanistan)
- `fa-IR` Persian (Iran)
- `pt-PT` Portuguese (Portugal)
- `pa-IN` Punjabi (India)
- `sr-RS` Serbian (Serbia)
- `sd-IN` Sindhi (India)
- `si-LK` Sinhala (Sri Lanka)
- `sk-SK` Slovak (Slovakia)
- `sl-SI` Slovenian (Slovenia)
- `es-419` Spanish (Latin America)
- `es-MX` Spanish (Mexico)
- `sw-KE` Swahili (Kenya)
- `sv-SE` Swedish (Sweden)
- `ur-PK` Urdu (Pakistan)

## Response Parameters

### [taskType](https://runware.ai/docs/models/google-gemini-3-1-flash-tts#response-tasktype)

- **Type**: `string`
- **Required**: true
- **Value**: `audioInference`

Type of the task.

### [taskUUID](https://runware.ai/docs/models/google-gemini-3-1-flash-tts#response-taskuuid)

- **Type**: `string`
- **Required**: true
- **Format**: `UUID v4`

UUID of the task.

### [audioUUID](https://runware.ai/docs/models/google-gemini-3-1-flash-tts#response-audiouuid)

- **Type**: `string`
- **Required**: true
- **Format**: `UUID v4`

UUID of the output audio.

### [audioURL](https://runware.ai/docs/models/google-gemini-3-1-flash-tts#response-audiourl)

- **Type**: `string`
- **Format**: `URI`

URL of the output audio.

### [audioBase64Data](https://runware.ai/docs/models/google-gemini-3-1-flash-tts#response-audiobase64data)

- **Type**: `string`

Base64-encoded audio data.

### [audioDataURI](https://runware.ai/docs/models/google-gemini-3-1-flash-tts#response-audiodatauri)

- **Type**: `string`
- **Format**: `URI`

Data URI of the output audio.

### [seed](https://runware.ai/docs/models/google-gemini-3-1-flash-tts#response-seed)

- **Type**: `integer`

The seed used for generation. If none was provided, shows the randomly generated seed.

### [cost](https://runware.ai/docs/models/google-gemini-3-1-flash-tts#response-cost)

- **Type**: `float`

Task cost in USD. Present when `includeCost` is set to `true` in the request.