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Version: v4.4.0

Other

Use any OpenAI-compatible TTS service with OpenReader, including self-hosted servers not covered by a dedicated guide.

Requirements​

Your service only needs an OpenAI-compatible speech endpoint:

  • POST /v1/audio/speech — required.
  • Voice listing is optional and auto-discovered from /v1/audio/voices, /v1/voices, or /v1/styles. If none respond, OpenReader falls back to default voices — the Kokoro voice set for Kokoro models, otherwise the standard OpenAI voices (alloy, echo, fable, onyx, nova, shimmer).

The endpoint may return mp3, wav, ogg, or flac — OpenReader normalizes non-mp3 audio to mp3 automatically. An API key is optional.

Known compatible implementations: Kokoro-FastAPI, KittenTTS-FastAPI, Orpheus-FastAPI, Supertonic.

Setup​

Recommended (auth + admin): Settings → Admin → Shared providers

  1. Add a shared provider with type custom-openai.
  2. Set API_BASE to your service base URL (typically ending in /v1).
  3. Set API key if your service requires authentication.
  4. Set a default model/voice supported by your backend.

Legacy bootstrap seed (optional, first boot only):

API_BASE=http://your-tts-server/v1
# API_KEY=optional-key-if-required

Users select the configured shared provider, model, and voice from Settings → TTS Provider.

TTS requests are server-side

API_BASE must be reachable from the Next.js server, not just the browser. In Docker, use http://host.docker.internal:<port>/v1 so OpenReader reaches the service's published port on your host. A container name only resolves if OpenReader and the TTS service share a Docker network (Docker Compose, --link, or a shared --network). localhost/127.0.0.1 will not work, since inside the container that points at the container itself.

Troubleshooting​

If voices don't load, confirm the server is reachable from the Next.js runtime and that at least one of /v1/audio/voices, /v1/voices, or /v1/styles returns a valid response. If none do, OpenReader falls back to default voices — synthesis still works as long as POST /v1/audio/speech succeeds.

References​