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Overview Models Agents Tools Audio & voice Production API reference

Create speech

POST/audio/speech

Generates audio from the input text.

Returns the audio file content, or a stream of audio events.

Body ParametersJSONExpand Collapse
input: string

The text to generate audio for. The maximum length is 4096 characters.

maxLength4096
model: string or SpeechModel

One of the available TTS models: tts-1, tts-1-hd, gpt-4o-mini-tts, or gpt-4o-mini-tts-2025-12-15.

One of the following:
string
SpeechModel = "tts-1" or "tts-1-hd" or "gpt-4o-mini-tts" or "gpt-4o-mini-tts-2025-12-15"
One of the following:
"tts-1"
"tts-1-hd"
"gpt-4o-mini-tts"
"gpt-4o-mini-tts-2025-12-15"
voice: string or "alloy" or "ash" or "ballad" or 10 more or object { id }

The voice to use when generating the audio. Supported built-in voices are alloy, ash, ballad, coral, echo, fable, onyx, nova, sage, shimmer, verse, marin, and cedar. You may also provide a custom voice object with an id, for example { "id": "voice_1234" }. Previews of the voices are available in the Text to speech guide. Custom voices must be created from audio samples. Voices created from text prompts are supported only in Live.

One of the following:
string
"alloy" or "ash" or "ballad" or 10 more

The voice to use when generating the audio. Supported built-in voices are alloy, ash, ballad, coral, echo, fable, onyx, nova, sage, shimmer, verse, marin, and cedar. You may also provide a custom voice object with an id, for example { "id": "voice_1234" }. Previews of the voices are available in the Text to speech guide. Custom voices must be created from audio samples. Voices created from text prompts are supported only in Live.

One of the following:
"alloy"
"ash"
"ballad"
"coral"
"echo"
"sage"
"shimmer"
"verse"
"marin"
"cedar"
"fable"
"onyx"
"nova"
ID object { id }

Custom voice reference.

id: string

The custom voice ID, e.g. voice_1234.

instructions: optional string

Control the voice of your generated audio with additional instructions. Does not work with tts-1 or tts-1-hd.

maxLength4096
response_format: optional "mp3" or "opus" or "aac" or 3 more

The format to audio in. Supported formats are mp3, opus, aac, flac, wav, and pcm.

One of the following:
"mp3"
"opus"
"aac"
"flac"
"wav"
"pcm"
speed: optional number

The speed of the generated audio. Select a value from 0.25 to 4.0. 1.0 is the default.

minimum0.25
maximum4
stream_format: optional "sse" or "audio"

The format to stream the audio in. Supported formats are sse and audio. sse is not supported for tts-1 or tts-1-hd.

One of the following:
"sse"
"audio"

Create speech

curl https://api.openai.com/v1/audio/speech \
  -H "Authorization: Bearer $OPENAI_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gpt-4o-mini-tts",
    "input": "The quick brown fox jumped over the lazy dog.",
    "voice": "alloy"
  }' \
  --output speech.mp3

Create speech

curl https://api.openai.com/v1/audio/speech \
  -H "Authorization: Bearer $OPENAI_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gpt-4o-mini-tts",
    "input": "The quick brown fox jumped over the lazy dog.",
    "voice": "alloy",
    "stream_format": "sse"
  }'
Returns Examples