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Google: Gemini 3.1 Flash TTS Preview

google/gemini-3.1-flash-tts-preview

Released Apr 24, 20268,192 context$1/M input tokens$20/M output tokens

Gemini 3.1 Flash TTS Preview is a text-to-speech model from Google, and a substantial generational step up from Gemini 2.5 Flash TTS. It takes text input and produces audio output across 70+ languages — nearly 3× the language coverage of its predecessor.

The headline addition is a system of 200+ inline audio tags (e.g. [whispers], [laughs], [excited]) that let developers steer delivery, emotion, and pacing mid-sentence, alongside a "director's chair" workflow in Google AI Studio for defining per-character Audio Profiles and scene-level context. It supports up to two speakers with independent voice and style configuration per speaker, outputs PCM audio at 24 kHz / 16-bit mono, and automatically watermarks all output with SynthID. Context window is 32k tokens.

Sample code and API for Gemini 3.1 Flash TTS Preview

OpenRouter normalizes requests and responses across providers for you.

OpenRouter provides a text-to-speech API that converts text into natural-sounding audio. Send text and a voice selection, and receive raw audio bytes in your chosen format.

The response is a raw audio stream (not JSON). The generation ID is returned in the X-Generation-Id response header for tracking.

Using third-party SDKs

For information about using third-party SDKs and frameworks with OpenRouter, please see our frameworks documentation.

See the Request docs for all possible fields, and Parameters for explanations of specific sampling parameters.