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POST
  1. After submission, a task_id will be returned. If you provided a callback_url, when the task status becomes finished or failed, a POST request will be sent to the callback_url.
  2. Regardless of whether callback_url is provided, you can retrieve the result through the unified Query Task Status endpoint.
Gemini 3.8 Flash-Lite TTS is Google’s high-throughput text-to-speech model. It turns text, or a scripted conversation between two speakers, into WAV audio with 30 preset voices, auto-detects the language (Google lists 101) and takes plain-language style instructions. Use it for read-aloud features, notifications, voice-agent prompts and other high-volume, everyday speech. Gemini 3.8 Flash-Lite TTS takes the same request fields as Gemini 3.8 Flash TTS, which Google positions for maximum voice fidelity and complex dialogue. Switch between them by changing model.

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Models

  • google/gemini-3.8-flash-lite/text-to-speech — Gemini 3.8 Flash-Lite text-to-speech for high-volume single-voice or two-speaker audio.

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Features

  • Text-to-speech with one voice, or a scripted dialogue between two speakers.
  • 30 preset voices, set per request or per speaker.
  • Plain-language style_instructions for tone, pace, accent and emotion, globally or per dialogue turn.
  • Automatic language detection (Google lists 101 languages).
  • WAV audio output.

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Input modes

  • Single speaker: send text and, optionally, voice (default Kore).
  • Two-speaker dialogue: send exactly two speakers and a list of turns. Do not send top-level text or voice in this mode.

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Required parameters

Single speaker:
  • text (string): The text to speak. Not blank.
Two-speaker dialogue:
  • speakers (object[]): Exactly two objects, each with only:
    • speaker_id (string): A non-empty alias, unique within the request, such as host.
    • voice (string): One of the Voice Presets.
  • turns (object[]): At least one line, in speaking order:
    • speaker_id (string): Must match one of the two speakers.
    • text (string): What that speaker says. Not blank.
    • style_instructions (string, optional): Direction for this line only.

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Optional parameters

  • voice (string): Single-speaker mode only. One of the Voice Presets. Default Kore.
  • style_instructions (string): Global direction for the whole request, such as Calm, warm documentary narration. Works in both modes.
  • enable_safety_checker (boolean): Run the upstream safety checker. Default true.

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Output

The finished task returns one WAV audio file in the files array of Query Task Status and the callback payload. The output format is fixed; there is no output_format field.

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Voice Presets

voice and speakers[].voice accept these 30 values (case-sensitive):
  • Achernar
  • Achird
  • Algenib
  • Algieba
  • Alnilam
  • Aoede
  • Autonoe
  • Callirrhoe
  • Charon
  • Despina
  • Enceladus
  • Erinome
  • Fenrir
  • Gacrux
  • Iapetus
  • Kore
  • Laomedeia
  • Leda
  • Orus
  • Pulcherrima
  • Puck
  • Rasalgethi
  • Sadachbia
  • Sadaltager
  • Schedar
  • Sulafat
  • Umbriel
  • Vindemiatrix
  • Zephyr
  • Zubenelgenubi

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Examples

  • Single-speaker read-aloud: a message summary read with voice: Puck.
  • Two-speaker support dialogue: agent (Kore) and caller (Charon) with a global style_instructions, plus a callback_url.

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Notes

  • Credits are reserved at submission and depend on the billable character count: text, the global style_instructions, and every turn’s text and style_instructions. Speaker IDs are not counted. A failed task is refunded in full. See the pricing page for current rates.
  • Flash-Lite is billed at a lower rate than Gemini 3.8 Flash TTS.
  • Dialogue supports exactly two speakers. A third speaker, a speaker_id in turns that is not in speakers, or top-level text/voice in a dialogue request returns 400.
  • Put delivery directions in style_instructions, not in text; the model may read directions inside text aloud.
  • output_format, language_code, temperature, seed and timestamps are not supported on this endpoint, and neither are voice cloning or custom voices.

Authorizations

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Authorization
string
header
required

All API endpoints require Bearer Token authentication

Get your API Key:

Go to Dashboard → API Key (API Key Management Page) to get your API Key

Add it to the request header:

Body

application/json
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model
string
required

Model ID. Use google/gemini-3.8-flash-lite/text-to-speech.

Example:

"google/gemini-3.8-flash-lite/text-to-speech"

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input
object
required

Generation parameters. Send text (single speaker) or speakers + turns (two-speaker dialogue), not both.

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callback_url
string<uri> | null

Optional public HTTP(S) endpoint that receives a POST when the task becomes finished or failed. HTTPS is recommended. Omit it, or send null or an empty string, to disable callbacks.

Example:

"https://your-domain.com/callback"

Response

Task submitted

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code
enum<integer>
required

HTTP status code.

Available options:
200
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data
object
required