Google Gemini 3.1 Flash TTS

About Google Gemini 3.1 Flash TTS

Google Gemini 3.1 Flash TTS is a text-to-speech API offering expressive, controllable speech output via inline audio tags and support for multi-speaker dialogue. It is available in preview through the Gemini API, Google AI Studio, and Vertex AI and supports more than 70 languages with per-locale accent control.

Review

This tool focuses on making speech output more expressive and easier to direct without complex post-processing. Inline audio tags allow developers to change tone, pacing, and delivery within a single input, while exportable voice configurations help keep character and delivery consistent across projects.

Key Features

• Inline audio tags for mid-sentence control of tone, pacing, and expression
• Native multi-speaker dialogue in a single API call
• Support for 70+ languages with per-locale accent control
• Exportable voice and scene configurations for reuse across projects
• SynthID watermarking to mark outputs as AI-generated

Pricing and Value

Google is offering the model in preview, and typical usage will likely follow API pricing models such as pay-as-you-go through the Gemini API or Vertex AI with possible free-tier access during the preview. The main value is reducing engineering work needed to produce expressive, multi-speaker audio; however, teams should factor in API costs, compute for large-scale use, and integration effort when assessing overall value.

Pros

• Fine-grained, inline control of delivery reduces the need for manual audio editing
• Built-in multi-speaker and exportable configs simplify complex dialogue workflows
• Broad language and accent coverage suits localization and multilingual products
• SynthID watermarking adds an attribution layer for generated audio

Cons

• Currently in preview, so stability, SLA, and final pricing are subject to change
• Integration and orchestration for complex projects can still require engineering effort
• Quality and expressiveness may vary by language or edge cases, requiring testing

Overall, Google Gemini 3.1 Flash TTS is well suited for developers and teams building voice agents, dubbing tools, or interactive audio experiences that need expressive, programmable speech. Organizations should pilot the preview and evaluate integration costs, language quality, and output attribution requirements before full production use.