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API Reference
Audio
Speech

Create speech

POST/audio/speech

Generates audio from the input text.

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.

Accepts one of the following:
UnionMember0 = string
SpeechModel = "tts-1" or "tts-1-hd" or "gpt-4o-mini-tts" or "gpt-4o-mini-tts-2025-12-15"
Accepts 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 7 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.

Accepts one of the following:
VoiceIDsShared = string or "alloy" or "ash" or "ballad" or 7 more
Accepts one of the following:
UnionMember0 = string
UnionMember1 = "alloy" or "ash" or "ballad" or 7 more
Accepts one of the following:
"alloy"
"ash"
"ballad"
"coral"
"echo"
"sage"
"shimmer"
"verse"
"marin"
"cedar"
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.

Accepts 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.

Accepts 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