Tool: Gemini 3.8 TTS Playground
Simon Willison’s Weblog
Subscribe
23rd September 2026
Tool
Gemini 3.8 TTS Playground — Test and experiment with Google's Gemini 3.8 text-to-speech API through an interactive playground where you can compose single-voice narration or multi-speaker conversations, preview the generated audio, and explore request and response details. Save your compose settings to bookmarkable URLs for easy sharing, and generate high-quality speech synthesis powered by your Gemini API key.
Google released two new Gemini text-to-speech models today - gemini-3.8-flash-tts and gemini-3.8-flash-lite-tts.
They come with a library of over 2,000 voices, plus the ability to create a custom voice with "just a 30-second audio sample of your voice or a voice you have the rights to use".
I vibe coded this bring-your-own-key playground interface with GPT-6 Astra, taking advantage of the open CORS policy of the underlying Gemini API.
A notable feature of the API is that it makes it easy to define a full conversation between multiple characters, each with different voices and voice style instructions.
Here's a short demo clip of a conversation between two pelicans debating if they should move to the Pacifica Pier. I had Claude 4.5 Opus write the script and generate a URL to render it using the tool.
Your browser does not support the audio element.
It took ~20 seconds to generate 1m 18s of audio using Gemini 3.8 Flash TTS (not the cheaper Flash-Lite), at a cost of 2.74 cents.
Recent articles
Claude Opus 5.5, GPT-6 Sol, GPT-6 Luna, and a new price war - 22nd September 2026
Jev introduces a new shape of LLM - System One, aka Decision Models - 21st September 2026
Generating running routes with GPT-6 Astra and ChatGPT Work - 12th September 2026
This is a beat by Simon Willison, posted on 23rd September 2026.
text-to-speech 20
gemini 198
Monthly briefing
Sponsor me for $10/month and get a curated email digest of the month's most important LLM developments.
Pay me to send you less!
Sponsor & subscribe
Disclosures
Colophon
©
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026