openai-speech/references/audio-api.md

Audio Speech API quick reference

Endpoint

• Create speech: POST /v1/audio/speech

Default model

• gpt-4o-mini-tts-2025-12-15

Other speech models (if requested)

• gpt-4o-mini-tts
• tts-1
• tts-1-hd

Core parameters

• model: speech model
• input: text to synthesize (max 4096 characters)
• voice: built-in voice name
• instructions: optional style directions (not supported for tts-1 or tts-1-hd)
• response_format: mp3, opus, aac, flac, wav, or pcm
• speed: 0.25 to 4.0

Built-in voices

• alloy, ash, ballad, cedar, coral, echo, fable, marin, nova, onyx, sage, shimmer, verse

Output notes

• Default format is mp3.
• pcm is raw 24 kHz 16-bit little-endian samples (no header).
• wav includes a header (better for quick playback).

Compliance note

• Provide a clear disclosure that the voice is AI-generated.