OpenAI TTS-1 HD
OpenAI's high-definition TTS model. Better quality for production use cases.
OpenAI TTS-1 HD is text-to-speech AI model from OpenAI, priced at €0.000 per 1M input tokens with a unknown context window.
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Examples
See what OpenAI TTS-1 HD can generate
Audiobook Passage
Input text:
"The old lighthouse keeper climbed the spiral stairs for the last time. Forty years of storms, shipwrecks, and solitary nights had carved deep lines into his face. But tonight, as the automated beacon flickered to life without him, he felt not relief but an aching emptiness—the sea no longer needed his watchful eyes."
Product Demo
Input text:
"Introducing AuraSync, the smart home hub that learns your routines. It dims the lights when you start a movie, adjusts the thermostat when you fall asleep, and brews your coffee exactly six minutes before your alarm. Your home, finally as intelligent as you are."
Pricing
API Integration
Use our OpenAI-compatible API to integrate OpenAI TTS-1 HD into your application.
npm install railwailimport railwail from "railwail";
const rw = railwail("YOUR_API_KEY");
// Simple — just pass a string
const reply = await rw.run("openai-tts-1-hd", "Hello! What can you do?");
console.log(reply);
// With message history
const reply2 = await rw.run("openai-tts-1-hd", [
{ role: "system", content: "You are a helpful assistant." },
{ role: "user", content: "Explain quantum computing simply." },
]);
console.log(reply2);
// Full response with usage info
const res = await rw.chat("openai-tts-1-hd", [
{ role: "user", content: "Hello!" },
], { temperature: 0.7, max_tokens: 500 });
console.log(res.choices[0].message.content);
console.log(res.usage);Deep dive — OpenAI's OpenAI TTS-1 HD
OpenAI was founded in December 2015 by Sam Altman, Elon Musk, Greg Brockman, Ilya Sutskever, Wojciech Zaremba and John Schulman as a non-profit AI research lab, restructured to capped-profit OpenAI LP in 2019. The company is best known for the GPT, DALL-E and Whisper model families and has raised more than $13B from Microsoft and billions more from Thrive Capital, Sequoia, Khosla and SoftBank, with a 2024 valuation above $157B. The TTS-1 HD model launched together with TTS-1 in November 2023 as the high-quality sibling, intended for offline audiobook, podcast and content-production workflows where fidelity matters more than latency. It powers the higher-quality option in the OpenAI audio endpoint and is exposed in tools like ChatGPT's Read Aloud feature on premium tiers.
Visit OpenAI →OpenAI TTS-1 HD is the high-fidelity variant of the TTS-1 family. It uses the same architectural family (Transformer-based neural-codec language-model TTS) and the same six voices (alloy, echo, fable, onyx, nova, shimmer) as TTS-1, but with a larger model and additional fine-tuning on long-form narration. The result is more natural prosody, clearer diction and better handling of long sentences, punctuation and emotional pacing, at roughly 2x the price ($0.030 per 1,000 characters) and noticeably higher latency. Output is 24 kHz in six formats (MP3, Opus, AAC, FLAC, WAV, PCM). Text input is capped at 4,096 characters per request, which is recommended to be split into paragraph chunks for very long narration. The model targets offline production: audiobooks, podcasts, training videos, accessibility narration. It does not support voice cloning.
- Parameters
- Undisclosed (larger than TTS-1)
- Context
- 4.1K tokens
- High-fidelity narration with natural prosody and emotional pacing
- Six recorded voices: alloy, echo, fable, onyx, nova, shimmer
- Multilingual: 50+ languages including English, German, Spanish, French, Italian, Japanese, Mandarin
- Six output formats including FLAC for lossless production
- Long-sentence handling tuned for audiobook-style narration
- Drop-in API-compatible with TTS-1 (just change the model name)
- Best for: audiobooks, podcasts, training content, voiceover, accessibility narration
Not disclosed. OpenAI states voices were recorded with paid professional actors; training corpus is a curated mix of recorded speech and licensed text-audio pairs.
License: Proprietary commercial API. Generated audio may be used commercially under the OpenAI Usage Policy; the six stock voices cannot be impersonated outside the API.
Known limitations
- No voice cloning
- 2x price of TTS-1 ($0.030 vs $0.015 per 1k chars)
- Higher latency unsuitable for real-time voice agents
- Hard cap of 4,096 characters per request
- Limited explicit prosody / emotion controls
Frequently asked questions
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