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POST
/
tts
/
sse
Text to Speech (SSE)
curl --request POST \
  --url https://api.cartesia.ai/tts/sse \
  --header 'Authorization: Bearer <token>' \
  --header 'Cartesia-Version: <cartesia-version>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "model_id": "<string>",
  "transcript": "<string>",
  "voice": {
    "mode": "id",
    "id": "<string>"
  },
  "output_format": {
    "container": "raw",
    "encoding": "pcm_f32le",
    "sample_rate": 8000
  },
  "language": "en",
  "context_id": "<string>",
  "add_timestamps": false,
  "add_phoneme_timestamps": false,
  "use_normalized_timestamps": true,
  "pronunciation_dict_id": "<string>",
  "generation_config": {
    "volume": 1,
    "speed": 1,
    "emotion": "neutral"
  },
  "speed": "normal"
}
'
{
  "type": "chunk",
  "done": false,
  "status_code": 206,
  "step_time": 123,
  "context_id": "50dc3b5e-5841-4aa1-9f94-60cfb9aead79",
  "data": "aSDinaTvuI8gbWludGxpZnk="
}

Documentation Index

Fetch the complete documentation index at: https://docs.cartesia.ai/llms.txt

Use this file to discover all available pages before exploring further.

Authorizations

​
Authorization
string
header
required

A short-lived access token to make API requests from a client.

Headers

​
Cartesia-Version
enum<string>
required

API version header.

Available options:
2026-03-01
Example:

"2026-03-01"

Body

application/json
​
model_id
string
required

The ID of the model to use for the generation. See Models for available models.

​
transcript
string
required
​
voice
TTSRequestVoiceSpecifier · object
required
​
output_format
SSEOutputFormat · object
required
​
language
enum<string>

The language that the given voice should speak the transcript in. For valid options, see Models.

Available options:
en,
fr,
de,
es,
pt,
zh,
ja,
hi,
it,
ko,
nl,
pl,
ru,
sv,
tr,
tl,
bg,
ro,
ar,
cs,
el,
fi,
hr,
ms,
sk,
da,
ta,
uk,
hu,
no,
vi,
bn,
th,
he,
ka,
id,
te,
gu,
kn,
ml,
mr,
pa
​
context_id
string | null

Optional context ID for this request.

​
add_timestamps
boolean | null
default:false

Whether to return word-level timestamps. If false (default), no word timestamps will be produced at all. If true, the server will return timestamp events containing word-level timing information.

​
add_phoneme_timestamps
boolean | null
default:false

Whether to return phoneme-level timestamps. If false (default), no phoneme timestamps will be produced. If true, the server will return timestamp events containing phoneme-level timing information.

​
use_normalized_timestamps
boolean | null

Whether to use normalized timestamps (True) or original timestamps (False).

​
pronunciation_dict_id
string | null

The ID of a pronunciation dictionary to use for the generation. Pronunciation dictionaries are supported by sonic-3 models and newer.

​
generation_config
GenerationConfig · object

Configure the various attributes of the generated speech. Available on sonic-3 and sonic-3.5 (with speed and volume temporarily disabled on sonic-3.5); not available on earlier models.

See Volume, Speed, and Emotion for a guide on this option.

​
speed
enum<string>
default:normal
deprecated

Use generation_config.speed for sonic-3. Speed setting for the model. Defaults to normal. This feature is experimental and may not work for all voices. Influences the speed of the generated speech. Faster speeds may reduce hallucination rate.

Available options:
slow,
normal,
fast

Response

200 - text/event-stream

Server-sent events stream. Each frame is data: <json>\n\n where the JSON payload matches TTSSSEEvent.

Audio data chunk.

​
type
enum<string>
required

Event type identifier.

Available options:
chunk
​
done
enum<boolean>
required

Whether this is the final event for the request. Always false for chunk events.

Available options:
false
​
data
string
required

Base64-encoded audio data.

​
step_time
number
required

Server-side processing time for this chunk in milliseconds.

​
status_code
integer
required

HTTP-style status code.

​
context_id
string | null

The context ID echoed back from the request, if one was provided.