OpenAI Text-to-Speech

OpenAI’s Text-to-Speech API generates remarkably natural speech with multiple voices, streaming support, and expressive control for developers.

Overview

OpenAI’s TTS offering provides developers with high-quality speech synthesis through simple API calls. The tts-1 model delivers low-latency generation ideal for real-time applications, while tts-1-hd produces broadcast-quality audio. Both support six built-in voices (Alloy, Echo, Fable, Onyx, Nova, Shimmer) and allow fine control over speed and expressiveness.

The newer gpt-4o-mini-tts model adds naturalness and instruction-based voice steering, letting developers describe desired tone and delivery style in plain language. Streaming support enables real-time applications like voice assistants and live narration, and the pricing per character makes it cost-effective for scale.

The API’s predictability is a feature: consistent voice output, straightforward rate limits, and JSON-native integration make it easy to embed in production systems. Because the same platform serves transcription and language models, developers can build complete voice experiences within one vendor relationship.

Key Features

• tts-1 for low latency and tts-1-hd for high-definition audio
• Six natural built-in voices with distinct characters
• gpt-4o-mini-tts with instruction-based expressive control
• Streaming support for real-time voice applications
• Simple REST API with JSON and audio output formats
• Speed control and format options (MP3, Opus, AAC, FLAC)
• Per-character pricing designed for scale
• Predictable voice consistency suitable for production systems
• Single-vendor integration with transcription and language models

Pricing

OpenAI TTS is priced per character processed, with tts-1 at approximately $0.015 per 1K characters and tts-1-hd at $0.030 per 1K characters. The gpt-4o-mini-tts model offers a middle ground in cost and quality. No free tier is provided for API usage. Costs scale linearly with characters processed, and there are no minimum commitments, making the API practical for startups and prototypes.

Who Is It For

OpenAI TTS is built for developers integrating voice into applications — chatbots, accessibility tools, content platforms, and voice assistants.

It suits teams already using OpenAI’s ecosystem who want consistent voice quality.

Accessibility teams use the API to add spoken output to applications for users with visual or reading impairments.

FAQ

Is OpenAI TTS free to use?

No — API usage is billed per character, though costs are low and predictable. ChatGPT’s voice features use related technology under consumer subscriptions.

Does OpenAI offer an API?

Yes, the Text-to-Speech API is available to all platform users with a simple REST interface supporting streaming.

How does OpenAI TTS compare to ElevenLabs?

OpenAI offers developer simplicity and ecosystem integration, while ElevenLabs leads on voice cloning, multilingual range, and emotional expressiveness.

Which audio formats does the API return?

The API can return speech in several formats including MP3, Opus, AAC, and FLAC, allowing developers to balance file size against quality for their specific application.