Supertonic is a lightning-fast, on-device text-to-speech system designed for extreme performance with minimal computational overhead. Powered by ONNX Runtime, it runs entirely on your device—no cloud, no API calls, no privacy concerns.

• 2026.01.22 - Voice Builder is now live! Turn your voice into a deployable, edge-native TTS with permanent ownership.

• 2026.01.06 - 🎉 Supertonic 2 released with multilingual support! Now supports English (en), Korean (ko), Spanish (es), Portuguese (pt), and French (fr). Demo | Models
• 2025.12.10 - Added supertonic PyPI package! Install via pip install supertonic. For details, visit supertonic-py documentation
• 2025.12.10 - Added 6 new voice styles (M3, M4, M5, F3, F4, F5). See Voices for details
• 2025.12.08 - Optimized ONNX models via OnnxSlim now available on Hugging Face Models
• 2025.11.24 - Added Flutter SDK support with macOS compatibility

• Demo
• Why Supertonic?
• Language Support
• Getting Started
• Performance
• Built with Supertonic
• Citation
• License

Watch Supertonic running on a Raspberry Pi, demonstrating on-device, real-time text-to-speech synthesis:

Experience Supertonic on an Onyx Boox Go 6 e-reader in airplane mode, achieving an average RTF of 0.3× with zero network dependency:

Turns any webpage into audio in under one second, delivering lightning-fast, on-device text-to-speech with zero network dependency—free, private, and effortless:

🎧 Try it now: Experience Supertonic in your browser with our Interactive Demo, or get started with pre-trained models from Hugging Face Hub

• ⚡ Blazingly Fast: Generates speech up to 167× faster than real-time on consumer hardware (M4 Pro)—unmatched by any other TTS system
• 🪶 Ultra Lightweight: Only 66M parameters, optimized for efficient on-device performance with minimal footprint
• 📱 On-Device Capable: Complete privacy and zero latency—all processing happens locally on your device
• 🎨 Natural Text Handling: Seamlessly processes numbers, dates, currency, abbreviations, and complex expressions without pre-processing
• ⚙️ Highly Configurable: Adjust inference steps, batch processing, and other parameters to match your specific needs
• 🧩 Flexible Deployment: Deploy seamlessly across servers, browsers, and edge devices with multiple runtime backends.

We provide ready-to-use TTS inference examples across multiple ecosystems:

For detailed usage instructions, please refer to the README.md in each language directory.

First, clone the repository:

git clone https://github.com/supertone-inc/supertonic.git
cd supertonic

Before running the examples, download the ONNX models and preset voices, and place them in the assets directory:

Note: The Hugging Face repository uses Git LFS. Please ensure Git LFS is installed and initialized before cloning or pulling large model files.

• macOS: brew install git-lfs && git lfs install
• Generic: see https://git-lfs.com for installers

git clone https://huggingface.co/Supertone/supertonic-2 assets

Python Example (Details)

cd py
uv sync
uv run example_onnx.py

Node.js Example (Details)

cd nodejs
npm install
npm start

Browser Example (Details)

cd web
npm install
npm run dev

Java Example (Details)

cd java
mvn clean install
mvn exec:java

C++ Example (Details)

cd cpp
mkdir build && cd build
cmake .. && cmake --build . --config Release
./example_onnx

C# Example (Details)

cd csharp
dotnet restore
dotnet run

Go Example (Details)

cd go
go mod download
go run example_onnx.go helper.go

Swift Example (Details)

cd swift
swift build -c release
.build/release/example_onnx

Rust Example (Details)

cd rust
cargo build --release
./target/release/example_onnx

iOS Example (Details)

cd ios/ExampleiOSApp
xcodegen generate
open ExampleiOSApp.xcodeproj

• In Xcode: Targets → ExampleiOSApp → Signing: select your Team
• Choose your iPhone as run destination → Build & Run

• Runtime: ONNX Runtime for cross-platform inference (CPU-optimized; GPU mode is not tested)
• Browser Support: onnxruntime-web for client-side inference
• Batch Processing: Supports batch inference for improved throughput
• Audio Output: Outputs 16-bit WAV files

We evaluated Supertonic's performance (with 2 inference steps) using two key metrics across input texts of varying lengths: Short (59 chars), Mid (152 chars), and Long (266 chars).

Metrics:

• Characters per Second: Measures throughput by dividing the number of input characters by the time required to generate audio. Higher is better.
• Real-time Factor (RTF): Measures the time taken to synthesize audio relative to its duration. Lower is better (e.g., RTF of 0.1 means it takes 0.1 seconds to generate one second of audio).

Notes:
API = Cloud-based API services (measured from Seoul)
Open = Open-source models
Supertonic (M4 pro - CPU) and (M4 pro - WebGPU): Tested with ONNX
Supertonic (RTX4090): Tested with PyTorch model
Kokoro: Tested on M4 Pro CPU with ONNX
NeuTTS Air: Tested on M4 Pro CPU with Q8-GGUF

Supertonic is designed to handle complex, real-world text inputs that contain numbers, currency symbols, abbreviations, dates, and proper nouns.

🎧 View audio samples more easily: Check out our Interactive Demo for a better viewing experience of all audio examples

Overview of Test Cases:

Note: These samples demonstrate how each system handles text normalization and pronunciation of complex expressions without requiring pre-processing or phonetic annotations.

The following papers describe the core technologies used in Supertonic. If you use this system in your research or find these techniques useful, please consider citing the relevant papers:

This paper introduces the overall architecture of SupertonicTTS, including the speech autoencoder, flow-matching based text-to-latent module, and efficient design choices.

@article{kim2025supertonic,
  title={SupertonicTTS: Towards Highly Efficient and Streamlined Text-to-Speech System},
  author={Kim, Hyeongju and Yang, Jinhyeok and Yu, Yechan and Ji, Seunghun and Morton, Jacob and Bous, Frederik and Byun, Joon and Lee, Juheon},
  journal={arXiv preprint arXiv:2503.23108},
  year={2025},
  url={https://arxiv.org/abs/2503.23108}
}

This paper presents Length-Aware Rotary Position Embedding (LARoPE), which improves text-speech alignment in cross-attention mechanisms.

@article{kim2025larope,
  title={Length-Aware Rotary Position Embedding for Text-Speech Alignment},
  author={Kim, Hyeongju and Lee, Juheon and Yang, Jinhyeok and Morton, Jacob},
  journal={arXiv preprint arXiv:2509.11084},
  year={2025},
  url={https://arxiv.org/abs/2509.11084}
}

This paper describes the self-purification technique for training flow matching models robustly with noisy or unreliable labels.

@article{kim2025spfm,
  title={Training Flow Matching Models with Reliable Labels via Self-Purification},
  author={Kim, Hyeongju and Yu, Yechan and Yi, June Young and Lee, Juheon},
  journal={arXiv preprint arXiv:2509.19091},
  year={2025},
  url={https://arxiv.org/abs/2509.19091}
}

This project's sample code is released under the MIT License. - see the LICENSE for details.

The accompanying model is released under the OpenRAIL-M License. - see the LICENSE file for details.

This model was trained using PyTorch, which is licensed under the BSD 3-Clause License but is not redistributed with this project. - see the LICENSE for details.

Copyright (c) 2026 Supertone Inc.