# Ondoku (音読さん)

> Ondoku (音読さん, ondoku3.com) is a text-to-speech web service. It offers two official HTTP APIs: the Standard TTS API (SLA: 99.0% monthly uptime) and the Advanced TTS API (Beta, SLA: 98.0% monthly uptime). Both authenticate with an access token in the `token` header.

The API documentation is published in English and Japanese with the same terms. A machine-readable OpenAPI 3.1 definition (in English) covers both APIs.

## Official APIs

- Standard TTS API: `POST https://ondoku3.com/text_to_speech_api/`. Official API. Synthesizes speech in 81 languages and regions with 692 voices and returns the URL of the generated MP3. SLA: 99.0% monthly uptime.
- Advanced TTS API (Beta): `POST https://ondoku3.com/api/advanced-tts/` creates an asynchronous job; `GET https://ondoku3.com/api/advanced-tts/jobs/{job_id}/` polls it. Official API in Beta with emotion and speaking-style control. SLA: 98.0% monthly uptime.

## Authentication

- Send your 64-character access token in the `token` header. Get it at https://ondoku3.com/ja/users/extension/ after signing in.
- Advanced TTS job polling sends the per-job `job_token` (returned by job creation) in the `X-Job-Token` header.

## Rate limits and quotas

- Standard TTS API: 30 requests per 60 seconds per client IP address (shared across all tokens used from the same IP).
- Standard TTS API: all four body fields `text`, `voice`, `speed`, and `pitch` are required.
- Advanced TTS API: the API accepts up to 400 characters per request on the free plan and 3,000 on paid plans. Job creation is limited to 10 requests per 60 seconds per client IP address (shared across all tokens used from the same IP).
- Both APIs consume the plan's monthly character allowance. See the pricing page for plans.

## SLA

- Uptime is measured per calendar month in JST. A 5-minute interval is downtime when it had requests and all of them returned HTTP 5xx. For the Advanced TTS API, both job creation and polling count; failed speech generation (job status `failed`) does not.
- Excluded: announced scheduled maintenance, outages of speech-synthesis providers or cloud infrastructure, client-side causes (HTTP 4xx, including rate limits and insufficient characters), and force majeure.
- If the SLA is missed, paid-plan users who apply via the contact form by the end of the following month receive 10% of their plan's monthly character allowance for that month. No cash refunds.
- The SLA covers uptime only, not response time.

## Change policy

- Breaking changes (removing fields, changing types or meaning, retiring endpoints) are announced 30 days in advance in the changelog section of each API documentation page.
- Notable backward-compatible changes such as new fields or voices are recorded in the same changelog after release (no advance notice).
- Urgent security fixes are an exception.

## Docs

- [API documentation index](https://ondoku3.com/en/developer/api/) ([Japanese](https://ondoku3.com/ja/developer/api/))
- [Standard TTS API](https://ondoku3.com/en/developer/api/standard-tts.html) ([Japanese](https://ondoku3.com/ja/developer/api/standard-tts.html)): authentication, request, response, errors, rate limits, SLA definition, changelog
- [Advanced TTS API, Beta](https://ondoku3.com/en/developer/api/advanced-tts.html) ([Japanese](https://ondoku3.com/ja/developer/api/advanced-tts.html)): job creation, polling, voices, errors, limits, SLA, changelog
- [Voice list for the Standard TTS API](https://ondoku3.com/en/developer/api/voices.html) ([Japanese](https://ondoku3.com/ja/developer/api/voices.html))
- [OpenAPI 3.1 definition](https://ondoku3.com/ja/developer/api/openapi.json): both APIs

## Pricing, terms, and support

- [Pricing (Japanese)](https://ondoku3.com/ja/pricing/)
- [Terms of service (Japanese)](https://ondoku3.com/ja/terms/)
- [Contact (Japanese)](https://ondoku3.com/ja/contact/)