Free local migration tool

Keep your Supertonic 3 voice after Voice Builder closed

Supertonic is the speech engine behind Natural voices. Voice Builder was Supertone’s separate custom voice service. It closed on August 31, 2026. If you kept a Supertonic 3 JSON backup, you can import it here and keep using the voice privately.

Voice Builder has closed. You can still import a Supertonic 3 JSON you downloaded earlier, but UnlimitedTTS cannot recover a file that was not backed up before shutdown.

Three steps to use a saved Voice Builder voice

The import is a migration of an existing purchased embedding—not new voice cloning. Everything happens on your device.

Find your Supertonic 3 JSON backup

Find the separately labeled Supertonic 3 JSON in the independent backup you retained before shutdown.
Import and preview locally

Choose the JSON, confirm its version and your usage rights, enter a display name, then complete a short browser-local preview before saving.
Keep an independent backup

Retain the original download. After import, open the voice manager and choose Download backup so browser storage is never your only copy.

What UnlimitedTTS imports—and what it does not

Supported

A purchased or otherwise legitimately obtained Supertonic 3 Voice Builder JSON.
Local schema validation, local preview and browser-local synthesis.
Re-exporting the canonical tensor-only backup.

Not supported

Supertonic 2 JSON as a supported drop-in v3 style. “v2-compatible” refers to the ONNX inference interface, not the voice embedding.
Recovering Play/API voices or files that were never downloaded.
Creating a new voice from reference audio.

Private by default, portable by design

UnlimitedTTS reads only the two style tensors needed for Supertonic 3. Source metadata is discarded, and the filename, display name, preview text and tensor values are never sent to analytics.

What stays local

The imported tensor data and your display name are saved in IndexedDB for this browser profile. Speech generation runs through Supertonic 3 using WebGPU or WebAssembly on your device.

What analytics records

Only aggregate funnel stages, normalized error codes, migration phase and whether storage is browser-local. No voice identity, filename, vector, checksum or text content is included.

Official references

These references document the former service and the Supertonic model. UnlimitedTTS is an independent project and is not endorsed by or affiliated with Supertone.

Supertonic Voice Builder migration FAQ

Which saved Supertonic file can I import?

Use a backup explicitly labeled Supertonic 3 JSON that you downloaded before Voice Builder closed. Supertonic 2 and 3 exports are model-specific even though their visible JSON structure can look the same.

Can I import a Voice Builder JSON after August 31, 2026?

Yes, if you already downloaded and retained the Supertonic 3 JSON. UnlimitedTTS imports an existing backup locally; it cannot recover a file that was never downloaded before Voice Builder closed.

Can my browser delete an imported voice?

Yes. Imported voices currently live in browser storage, not an UnlimitedTTS account. Clearing site data, private-browsing cleanup, a browser profile reset, storage pressure, or occasionally a browser update can remove that data. Keep the original JSON and a separate backup.

Does the imported voice file leave my device?

No in the current local mode. Validation, preview, storage and Supertonic 3 speech generation happen in your browser. UnlimitedTTS analytics never receives the filename, voice name, metadata, tensor values or checksum.

Are Supertonic 2 voice files compatible with Supertonic 3?

Not as an officially supported drop-in voice style. Supertone's v2-compatible statement refers to the public ONNX inference interface, while its Voice Builder documentation describes separate, version-specific JSON files. A v2 file can have the same shape and pass structural validation, but that does not prove its embedding represents the same voice in v3. Supertone has not published a direct v2-to-v3 embedding conversion.

Can I export an imported voice from UnlimitedTTS again?

Yes. Open the importer, find the saved voice and choose Download backup. The exported file contains the canonical voice tensors without the source metadata that may have appeared in the original file.

Keep using the backup you saved

If you retained a Supertonic 3 JSON backup, you can still import, preview and use it locally.

Updated October 2, 2026 for the closed Voice Builder service. Product names and trademarks belong to their respective owners. This page provides engineering and migration guidance, not legal advice.