Hear it before you build on it
Four of the 54 preset voices, synthesized by this API. English (US & UK), Spanish, French, Hindi, Italian, Japanese, Portuguese and Chinese.
Full list: GET /v1/voices — no key required.
One credit, one character. That's the whole model.
No seats, no minutes, no per-voice fees. Failed syntheses are refunded automatically.
Free
- All 54 voices, all languages
- Full API access
- No credit card required
Pay as you go
- $0.05 per 10,000 characters
- Top up any amount, any time
- No subscription, no expiry
Pro
- ~$0.04 per 10,000 characters
- Priority processing
- Commercial support
Shipping in three requests
Plain REST. Plain WAV. Any language, any stack — if it can send HTTP, it can speak.
Issue a key
curl -X POST https://api.opnvoice.cloud/v1/keys \ -H "content-type: application/json" -d '{"email":"you@company.com"}' → {"api_key":"sk_tts_…","free_credits":5000}
Synthesize
voice defaults to af_sarah, speed 0.5–2.0, up to 5,000 chars per request.
curl -X POST https://api.opnvoice.cloud/v1/tts \ -H "x-api-key: sk_tts_…" -H "content-type: application/json" \ -d '{"text":"Hello from OpnVoice.","voice":"af_sarah","speed":1.0}' \ -o hello.wav → WAV, 24 kHz mono · header x-credits-remaining tells you your balance
Handle four status codes
| Status | Meaning | What to do |
|---|---|---|
| 200 | Audio returned | Ship it |
| 400 | Empty text, >5,000 chars, or unknown voice | Fix the request — credits refunded |
| 401 | Missing or invalid API key | Check the x-api-key header |
| 402 | Out of credits | Top up via the link in the response body |
The questions that matter
Who owns the generated audio?
You do — 100% of IP and commercial rights are assigned to the requester (Terms, §1). Use it in products, ads, videos, games. No attribution, no royalties, ever.
Is this really safe for commercial use?
Yes. The model (Kokoro-82M) is Apache-2.0 and the runtime (kokoro-onnx) is MIT — both permit commercial use. We carry the license notice in every response's x-license header, so the compliance burden stays on our side of the API.
Do you offer voice cloning?
No, deliberately. Only pre-approved preset voices are exposed — there is no cloning code in the stack. That's a large part of why the output is legally safe to use.
What are the rate limits?
Your credit balance is the limit — one character costs one credit, checked atomically per request. If a synthesis fails on our side, the credits are refunded automatically.
What audio format do I get?
WAV, 24 kHz, 16-bit mono — ready for any player or pipeline. MP3 output is on the roadmap; converting with ffmpeg is one line in the meantime.