Using OpenAI for Text-to-Speech

This guide covers how to use OpenAI's official Text-to-Speech API with Open WebUI. This is the simplest setup if you already have an OpenAI API key.

Looking for STT?

See the companion guide: Using OpenAI for Speech-to-Text

Requirements

• An OpenAI API key with access to the Audio API
• Open WebUI installed and running

Quick Setup (UI)

1. Click your profile icon (bottom-left corner)
2. Select Admin Panel
3. Click Settings → Audio tab
4. Configure the following:

Setting	Value
Text-to-Speech Engine	OpenAI
API Base URL	https://api.openai.com/v1
API Key	Your OpenAI API key
TTS Model	tts-1 or tts-1-hd
TTS Voice	Choose from available voices

5. Click Save

Available Models

Model	Description	Best For
tts-1	Standard quality, lower latency	Real-time applications, faster responses
tts-1-hd	Higher quality audio	Pre-recorded content, premium audio quality

Available Voices

OpenAI provides 6 built-in voices:

Voice	Description
alloy	Neutral, balanced
echo	Warm, conversational
fable	Expressive, British accent
onyx	Deep, authoritative
nova	Friendly, upbeat
shimmer	Soft, gentle

tip

Try different voices to find the one that best suits your use case. You can preview voices in OpenAI's documentation.

Per-Model TTS Voice

You can assign a specific TTS voice to individual models, allowing different AI personas to have distinct voices. This is configured in the Model Editor.

Setting a Model-Specific Voice

1. Go to Workspace > Models
2. Click the Edit (pencil) icon on the model you want to configure
3. Scroll down to find the TTS Voice field
4. Enter the voice name (e.g., alloy, echo, shimmer, onyx, nova, fable)
5. Click Save

Voice Priority

When playing TTS audio, Open WebUI uses the following priority:

1. Model-specific TTS voice (if set in Model Editor)
2. User's personal voice setting (if configured in user settings)
3. System default voice (configured by admin)

This allows admins to give each AI persona a consistent voice while still letting users override with their personal preference when no model-specific voice is set.

Use Cases

• Character personas: Give a "British Butler" model the fable voice, while an "Energetic Assistant" uses nova
• Language learning: Assign appropriate voices for different language tutors
• Accessibility: Set clearer voices for models designed for accessibility use cases

Environment Variables Setup

If you prefer to configure via environment variables:

services:
  open-webui:
    image: ghcr.io/open-webui/open-webui:main
    environment:
      - AUDIO_TTS_ENGINE=openai
      - AUDIO_TTS_OPENAI_API_BASE_URL=https://api.openai.com/v1
      - AUDIO_TTS_OPENAI_API_KEY=sk-...
      - AUDIO_TTS_MODEL=tts-1
      - AUDIO_TTS_VOICE=alloy
    # ... other configuration

All TTS Environment Variables

Variable	Description	Default
AUDIO_TTS_ENGINE	Set to openai	empty
AUDIO_TTS_OPENAI_API_BASE_URL	OpenAI API base URL	https://api.openai.com/v1
AUDIO_TTS_OPENAI_API_KEY	Your OpenAI API key	empty
AUDIO_TTS_MODEL	TTS model (tts-1 or tts-1-hd)	tts-1
AUDIO_TTS_VOICE	Voice to use	alloy

Using OpenRouter as a Text-to-Speech Provider

Open WebUI's OpenAI TTS engine is compatible with any service that implements the OpenAI Audio API, including OpenRouter. This section explains how to configure OpenRouter as your TTS provider and how to avoid a common 400 Bad Request error.

Why the 400 Error Happens

OpenRouter's /audio/speech endpoint defaults response_format to pcm when the field is omitted. Open WebUI does not send response_format in its request payload, so OpenRouter returns raw PCM audio, which Open WebUI cannot play back — resulting in a 400 Bad Request.

The fix is to explicitly request MP3 by adding {"response_format": "mp3"} to the OpenAI Params field (extra parameters) in the TTS settings.

Quick Setup (UI)

1. Click your profile icon (bottom-left corner)
2. Select Admin Panel
3. Click Settings → Audio tab → Text-to-Speech Settings
4. Configure the following:

Setting	Value
Text-to-Speech Engine	OpenAI
API Base URL	https://openrouter.ai/api/v1
API Key	Your OpenRouter API key (sk-or-...)
TTS Model	Any OpenRouter TTS model, e.g. openai/tts-1
TTS Voice	Choose from available voices
OpenAI Params	{"response_format": "mp3"}

important

The OpenAI Params field must contain {"response_format": "mp3"}. Without it, OpenRouter defaults to pcm, and speech requests fail with a 400 Bad Request error.

5. Click Save

Environment Variables Setup

If you prefer to configure via environment variables, add the parameters JSON via AUDIO_TTS_OPENAI_PARAMS:

services:
  open-webui:
    image: ghcr.io/open-webui/open-webui:main
    environment:
      - AUDIO_TTS_ENGINE=openai
      - AUDIO_TTS_OPENAI_API_BASE_URL=https://openrouter.ai/api/v1
      - AUDIO_TTS_OPENAI_API_KEY=sk-or-...
      - AUDIO_TTS_MODEL=openai/tts-1
      - AUDIO_TTS_VOICE=alloy
      - AUDIO_TTS_OPENAI_PARAMS={"response_format":"mp3"}
    # ... other configuration

info

OpenRouter supports mp3 and pcm output formats. Always select mp3 in Open WebUI — PCM output is intended for real-time streaming pipelines and cannot be played back by Open WebUI.

Testing TTS

1. Start a new chat
2. Send a message to any model
3. Click the speaker icon on the AI response to hear it read aloud

Response Splitting

When reading long responses, Open WebUI can split text into chunks before sending them to the TTS engine. This is configured in Settings > Admin > Experience > Audio under Response Splitting.

Option	Description
Punctuation (default)	Splits at sentence boundaries: periods (.), exclamation marks (!), question marks (?), and newlines. Best for natural pacing.
Paragraphs	Splits only at paragraph breaks (double newlines). Results in longer audio chunks.
None	Sends the entire response as one chunk. May cause delays before audio starts on long responses.

tip

Punctuation mode is recommended for most use cases. It provides the best balance of streaming performance (audio starts quickly) and natural speech pacing.

Troubleshooting

No Audio Plays

1. Check your OpenAI API key is valid and has Audio API access
2. Verify the API Base URL is correct (https://api.openai.com/v1)
3. Check browser console (F12) for errors

Audio Quality Issues

• Switch from tts-1 to tts-1-hd for higher quality
• Note: tts-1-hd has slightly higher latency

Rate Limits

OpenAI has rate limits on the Audio API. If you're hitting limits:

• Consider caching common phrases
• Use tts-1 instead of tts-1-hd (uses fewer tokens)

For more troubleshooting, see the Audio Troubleshooting Guide.

Cost Considerations

OpenAI charges per character for TTS. See OpenAI Pricing for current rates. Note that tts-1-hd costs more than tts-1.

info

For a free alternative, consider OpenAI Edge TTS which uses Microsoft's free Edge browser TTS.