Voice

What it does

Natural speech, generated locally.

• Default small is Kokoro 82M (StyleTTS 2): American, British, Spanish and French. Runs on Transformers.js directly, no kokoro-js. fp32 on WebGPU (fp16 gives NaN on the v4 runtime), q8 on WASM.
• Pass size: "multi" for Supertonic 2 (Supertone, 2026): one ~262 MB model for English, Korean, Spanish, Portuguese and French at 44.1 kHz, 10 preset voices (st_f1…st_m5). Pass language per call.
• Supertonic 2 is OpenRAIL-M: open weights with use restrictions (no impersonation, no deception, no illegal use). The rest of the TTS sizes are Apache-2.0.
• Pass size: "tiny" for KittenTTS nano (~28 MB, 8 English voices, WASM).
• Audio streams sentence by sentence via speakStream. WebGPU is several times faster on small and multi; WASM works everywhere.
• Pass voice to pick a speaker (af_heart / bella / st_f1). Kokoro Spanish and French download a local eSpeak-NG WASM (~18 MB) on first use. Nothing is uploaded.

Specifications

Package

runonweb/tts

Base model

Kokoro 82M · hexgrad

License

Apache-2.0

Weights

onnx-community/Kokoro-82M-v1.0-ONNX

Download

~326 MB / ~92 MB (small)multi ~262 MBtiny ~28 MB

Quantization

fp32 on WebGPUq8 on WASM (multi is fp32, tiny is WASM)

Backend

WebGPUWASM fallback

Input

Text

Get started with runonweb/tts

pnpm add runonweb

npm install runonweb

bun add runonweb

yarn add runonweb

import { TextToSpeech } from 'runonweb/tts'

const tts = new TextToSpeech({ size: 'small', voice: 'af_heart' })
await tts.load()

for await (const chunk of tts.speakStream('Hello from the browser')) {
  // chunk.audio is 24 kHz PCM. Play as it arrives
}

const wav = await tts.speakToBlob('Hola mundo', { voice: 'ef_dora' })
new Audio(URL.createObjectURL(wav)).play()

// Supertonic 2: one model, five languages, 44.1 kHz
const multi = new TextToSpeech({ size: 'multi', voice: 'st_f1' })
const pt = await multi.speakToBlob('Olá do navegador', { language: 'pt' })

tts.dispose()

Same shape everywhere: construct, load(), run, dispose(). Pass onProgressto show download progress on first use.

Questions about Voice