Model comparison
Compare Gemini 3.8 Flash TTS and Inworld Realtime TTS-2 using the same provider-sourced voice & realtime rubric. No mystery score and no invented benchmark ranking.
Quick take
Google's speech-generation model for expressive narration, character voices and dialogue in 130 languages.
Put delivery instructions in speech_metadata, not the spoken script. Voice replication requires the speaker's consent; regional restrictions apply. Generated audio carries SynthID watermarking.
Inworld's newest expressive realtime text-to-speech model, designed to remember conversational delivery and speak in more than 100 languages.
This is the speech layer, not a complete agent. Inworld's current zero-data-retention page does not explicitly list TTS-2, so confirm coverage before sending sensitive text or voice data.
Compare the published facts
Values use each provider's own published units and limits. A blank means the provider did not publish a directly comparable value in the sources reviewed.
| Voice & realtime | Gemini 3.8 Flash TTS | Inworld Realtime TTS-2 |
|---|---|---|
| Price basisToken-, character-, or minute-based price for the listed access route. | $0.50 text input · $9 audio output / 1M tokens | $25 / 1M chars on demand; volume discounts |
| Interaction modeSpeech-to-speech, audio-to-audio, or streamed text-to-speech behavior. | Text-to-speech with two-speaker dialogue | Steerable realtime TTS with prior-audio context |
| Published latencyProvider-published measurement with its stated exclusions; not a Cody test. | Not published | Under 200ms median TTFA |
| LanguagesProvider-documented language coverage or a clear unpublished marker. | 130 languages | 100+ with mid-utterance switching |
| Tools & controlNative function calling, reasoning, or speech-control features. | Voice design and replication; no function calling | Voice direction, design, cloning, non-verbals |
| Context or input limitDocumented token or character limit where it is meaningful. | 8,192 input · 16,384 output tokens | Not published |
How to choose
Start with the job you need to complete, then validate cost, access, and policy details on your exact provider route.
Google says paid Gemini API prompts and responses are not used to improve its products. Unpaid-service content generally may be used, with different treatment for EEA, UK, and Swiss users; check the current terms for your account and region.
Provider and API links
Inworld advertises zero data retention as an enterprise add-on, but its currently published ZDR support page names only TTS-1.5 Mini and Max. Confirm TTS-2 coverage directly before sending regulated or confidential text.
Frequently asked questions
Gemini 3.8 Flash TTS: Google's speech-generation model for expressive narration, character voices and dialogue in 130 languages. Inworld Realtime TTS-2: Inworld's newest expressive realtime text-to-speech model, designed to remember conversational delivery and speak in more than 100 languages.
Consider Gemini 3.8 Flash TTS when your priority is Audiobooks. Consider Inworld Realtime TTS-2 when your priority is Realtime companions and support voices. Test both with your own data and provider route before committing.
No. This comparison aligns provider-published facts for the Voice & realtime category. It does not claim a universal winner or combine incompatible third-party benchmark scores.
