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 @- <<EOF
{
  "model_id": "sonic-3.5",
  "transcript": "Hi there, it's awesome to meet you.",
  "voice": {
    "mode": "id",
    "id": "db6b0ed5-d5d3-463d-ae85-518a07d3c2b4"
  },
  "output_format": {
    "container": "raw"
  },
  "language": "en",
  "locale": "en-GB",
  "normalization": "auto",
  "add_timestamps": false,
  "add_phoneme_timestamps": false,
  "use_normalized_timestamps": true,
  "pronunciation_dict_id": "<string>",
  "generation_config": {
    "volume": 1,
    "speed": 1
  },
  "speed": "normal",
  "context_id": "<string>"
}
EOF

import requests

url = "https://api.cartesia.ai/tts/sse"

payload = {
    "model_id": "sonic-3.5",
    "transcript": "Hi there, it's awesome to meet you.",
    "voice": {
        "mode": "id",
        "id": "db6b0ed5-d5d3-463d-ae85-518a07d3c2b4"
    },
    "output_format": { "container": "raw" },
    "language": "en",
    "locale": "en-GB",
    "normalization": "auto",
    "add_timestamps": False,
    "add_phoneme_timestamps": False,
    "use_normalized_timestamps": True,
    "pronunciation_dict_id": "<string>",
    "generation_config": {
        "volume": 1,
        "speed": 1
    },
    "speed": "normal",
    "context_id": "<string>"
}
headers = {
    "Cartesia-Version": "<cartesia-version>",
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

response = requests.post(url, json=payload, headers=headers)

print(response.text)

const options = {
  method: 'POST',
  headers: {
    'Cartesia-Version': '<cartesia-version>',
    Authorization: 'Bearer <token>',
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({
    model_id: 'sonic-3.5',
    transcript: 'Hi there, it\'s awesome to meet you.',
    voice: {mode: 'id', id: 'db6b0ed5-d5d3-463d-ae85-518a07d3c2b4'},
    output_format: {container: 'raw'},
    language: 'en',
    locale: 'en-GB',
    normalization: 'auto',
    add_timestamps: false,
    add_phoneme_timestamps: false,
    use_normalized_timestamps: true,
    pronunciation_dict_id: '<string>',
    generation_config: {volume: 1, speed: 1},
    speed: 'normal',
    context_id: '<string>'
  })
};

fetch('https://api.cartesia.ai/tts/sse', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://api.cartesia.ai/tts/sse",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => json_encode([
    'model_id' => 'sonic-3.5',
    'transcript' => 'Hi there, it\'s awesome to meet you.',
    'voice' => [
        'mode' => 'id',
        'id' => 'db6b0ed5-d5d3-463d-ae85-518a07d3c2b4'
    ],
    'output_format' => [
        'container' => 'raw'
    ],
    'language' => 'en',
    'locale' => 'en-GB',
    'normalization' => 'auto',
    'add_timestamps' => false,
    'add_phoneme_timestamps' => false,
    'use_normalized_timestamps' => true,
    'pronunciation_dict_id' => '<string>',
    'generation_config' => [
        'volume' => 1,
        'speed' => 1
    ],
    'speed' => 'normal',
    'context_id' => '<string>'
  ]),
  CURLOPT_HTTPHEADER => [
    "Authorization: Bearer <token>",
    "Cartesia-Version: <cartesia-version>",
    "Content-Type: application/json"
  ],
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://api.cartesia.ai/tts/sse"

	payload := strings.NewReader("{\n  \"model_id\": \"sonic-3.5\",\n  \"transcript\": \"Hi there, it's awesome to meet you.\",\n  \"voice\": {\n    \"mode\": \"id\",\n    \"id\": \"db6b0ed5-d5d3-463d-ae85-518a07d3c2b4\"\n  },\n  \"output_format\": {\n    \"container\": \"raw\"\n  },\n  \"language\": \"en\",\n  \"locale\": \"en-GB\",\n  \"normalization\": \"auto\",\n  \"add_timestamps\": false,\n  \"add_phoneme_timestamps\": false,\n  \"use_normalized_timestamps\": true,\n  \"pronunciation_dict_id\": \"<string>\",\n  \"generation_config\": {\n    \"volume\": 1,\n    \"speed\": 1\n  },\n  \"speed\": \"normal\",\n  \"context_id\": \"<string>\"\n}")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("Cartesia-Version", "<cartesia-version>")
	req.Header.Add("Authorization", "Bearer <token>")
	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

HttpResponse<String> response = Unirest.post("https://api.cartesia.ai/tts/sse")
  .header("Cartesia-Version", "<cartesia-version>")
  .header("Authorization", "Bearer <token>")
  .header("Content-Type", "application/json")
  .body("{\n  \"model_id\": \"sonic-3.5\",\n  \"transcript\": \"Hi there, it's awesome to meet you.\",\n  \"voice\": {\n    \"mode\": \"id\",\n    \"id\": \"db6b0ed5-d5d3-463d-ae85-518a07d3c2b4\"\n  },\n  \"output_format\": {\n    \"container\": \"raw\"\n  },\n  \"language\": \"en\",\n  \"locale\": \"en-GB\",\n  \"normalization\": \"auto\",\n  \"add_timestamps\": false,\n  \"add_phoneme_timestamps\": false,\n  \"use_normalized_timestamps\": true,\n  \"pronunciation_dict_id\": \"<string>\",\n  \"generation_config\": {\n    \"volume\": 1,\n    \"speed\": 1\n  },\n  \"speed\": \"normal\",\n  \"context_id\": \"<string>\"\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://api.cartesia.ai/tts/sse")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["Cartesia-Version"] = '<cartesia-version>'
request["Authorization"] = 'Bearer <token>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"model_id\": \"sonic-3.5\",\n  \"transcript\": \"Hi there, it's awesome to meet you.\",\n  \"voice\": {\n    \"mode\": \"id\",\n    \"id\": \"db6b0ed5-d5d3-463d-ae85-518a07d3c2b4\"\n  },\n  \"output_format\": {\n    \"container\": \"raw\"\n  },\n  \"language\": \"en\",\n  \"locale\": \"en-GB\",\n  \"normalization\": \"auto\",\n  \"add_timestamps\": false,\n  \"add_phoneme_timestamps\": false,\n  \"use_normalized_timestamps\": true,\n  \"pronunciation_dict_id\": \"<string>\",\n  \"generation_config\": {\n    \"volume\": 1,\n    \"speed\": 1\n  },\n  \"speed\": \"normal\",\n  \"context_id\": \"<string>\"\n}"

response = http.request(request)
puts response.read_body

{
  "type": "chunk",
  "done": false,
  "status_code": 206,
  "step_time": 123,
  "context_id": "50dc3b5e-5841-4aa1-9f94-60cfb9aead79",
  "data": "aSDinaTvuI8gbWludGxpZnk="
}

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 @- <<EOF
{
  "model_id": "sonic-3.5",
  "transcript": "Hi there, it's awesome to meet you.",
  "voice": {
    "mode": "id",
    "id": "db6b0ed5-d5d3-463d-ae85-518a07d3c2b4"
  },
  "output_format": {
    "container": "raw"
  },
  "language": "en",
  "locale": "en-GB",
  "normalization": "auto",
  "add_timestamps": false,
  "add_phoneme_timestamps": false,
  "use_normalized_timestamps": true,
  "pronunciation_dict_id": "<string>",
  "generation_config": {
    "volume": 1,
    "speed": 1
  },
  "speed": "normal",
  "context_id": "<string>"
}
EOF

import requests

url = "https://api.cartesia.ai/tts/sse"

payload = {
    "model_id": "sonic-3.5",
    "transcript": "Hi there, it's awesome to meet you.",
    "voice": {
        "mode": "id",
        "id": "db6b0ed5-d5d3-463d-ae85-518a07d3c2b4"
    },
    "output_format": { "container": "raw" },
    "language": "en",
    "locale": "en-GB",
    "normalization": "auto",
    "add_timestamps": False,
    "add_phoneme_timestamps": False,
    "use_normalized_timestamps": True,
    "pronunciation_dict_id": "<string>",
    "generation_config": {
        "volume": 1,
        "speed": 1
    },
    "speed": "normal",
    "context_id": "<string>"
}
headers = {
    "Cartesia-Version": "<cartesia-version>",
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

response = requests.post(url, json=payload, headers=headers)

print(response.text)

const options = {
  method: 'POST',
  headers: {
    'Cartesia-Version': '<cartesia-version>',
    Authorization: 'Bearer <token>',
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({
    model_id: 'sonic-3.5',
    transcript: 'Hi there, it\'s awesome to meet you.',
    voice: {mode: 'id', id: 'db6b0ed5-d5d3-463d-ae85-518a07d3c2b4'},
    output_format: {container: 'raw'},
    language: 'en',
    locale: 'en-GB',
    normalization: 'auto',
    add_timestamps: false,
    add_phoneme_timestamps: false,
    use_normalized_timestamps: true,
    pronunciation_dict_id: '<string>',
    generation_config: {volume: 1, speed: 1},
    speed: 'normal',
    context_id: '<string>'
  })
};

fetch('https://api.cartesia.ai/tts/sse', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://api.cartesia.ai/tts/sse",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => json_encode([
    'model_id' => 'sonic-3.5',
    'transcript' => 'Hi there, it\'s awesome to meet you.',
    'voice' => [
        'mode' => 'id',
        'id' => 'db6b0ed5-d5d3-463d-ae85-518a07d3c2b4'
    ],
    'output_format' => [
        'container' => 'raw'
    ],
    'language' => 'en',
    'locale' => 'en-GB',
    'normalization' => 'auto',
    'add_timestamps' => false,
    'add_phoneme_timestamps' => false,
    'use_normalized_timestamps' => true,
    'pronunciation_dict_id' => '<string>',
    'generation_config' => [
        'volume' => 1,
        'speed' => 1
    ],
    'speed' => 'normal',
    'context_id' => '<string>'
  ]),
  CURLOPT_HTTPHEADER => [
    "Authorization: Bearer <token>",
    "Cartesia-Version: <cartesia-version>",
    "Content-Type: application/json"
  ],
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://api.cartesia.ai/tts/sse"

	payload := strings.NewReader("{\n  \"model_id\": \"sonic-3.5\",\n  \"transcript\": \"Hi there, it's awesome to meet you.\",\n  \"voice\": {\n    \"mode\": \"id\",\n    \"id\": \"db6b0ed5-d5d3-463d-ae85-518a07d3c2b4\"\n  },\n  \"output_format\": {\n    \"container\": \"raw\"\n  },\n  \"language\": \"en\",\n  \"locale\": \"en-GB\",\n  \"normalization\": \"auto\",\n  \"add_timestamps\": false,\n  \"add_phoneme_timestamps\": false,\n  \"use_normalized_timestamps\": true,\n  \"pronunciation_dict_id\": \"<string>\",\n  \"generation_config\": {\n    \"volume\": 1,\n    \"speed\": 1\n  },\n  \"speed\": \"normal\",\n  \"context_id\": \"<string>\"\n}")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("Cartesia-Version", "<cartesia-version>")
	req.Header.Add("Authorization", "Bearer <token>")
	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

HttpResponse<String> response = Unirest.post("https://api.cartesia.ai/tts/sse")
  .header("Cartesia-Version", "<cartesia-version>")
  .header("Authorization", "Bearer <token>")
  .header("Content-Type", "application/json")
  .body("{\n  \"model_id\": \"sonic-3.5\",\n  \"transcript\": \"Hi there, it's awesome to meet you.\",\n  \"voice\": {\n    \"mode\": \"id\",\n    \"id\": \"db6b0ed5-d5d3-463d-ae85-518a07d3c2b4\"\n  },\n  \"output_format\": {\n    \"container\": \"raw\"\n  },\n  \"language\": \"en\",\n  \"locale\": \"en-GB\",\n  \"normalization\": \"auto\",\n  \"add_timestamps\": false,\n  \"add_phoneme_timestamps\": false,\n  \"use_normalized_timestamps\": true,\n  \"pronunciation_dict_id\": \"<string>\",\n  \"generation_config\": {\n    \"volume\": 1,\n    \"speed\": 1\n  },\n  \"speed\": \"normal\",\n  \"context_id\": \"<string>\"\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://api.cartesia.ai/tts/sse")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["Cartesia-Version"] = '<cartesia-version>'
request["Authorization"] = 'Bearer <token>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"model_id\": \"sonic-3.5\",\n  \"transcript\": \"Hi there, it's awesome to meet you.\",\n  \"voice\": {\n    \"mode\": \"id\",\n    \"id\": \"db6b0ed5-d5d3-463d-ae85-518a07d3c2b4\"\n  },\n  \"output_format\": {\n    \"container\": \"raw\"\n  },\n  \"language\": \"en\",\n  \"locale\": \"en-GB\",\n  \"normalization\": \"auto\",\n  \"add_timestamps\": false,\n  \"add_phoneme_timestamps\": false,\n  \"use_normalized_timestamps\": true,\n  \"pronunciation_dict_id\": \"<string>\",\n  \"generation_config\": {\n    \"volume\": 1,\n    \"speed\": 1\n  },\n  \"speed\": \"normal\",\n  \"context_id\": \"<string>\"\n}"

response = http.request(request)
puts response.read_body

{
  "type": "chunk",
  "done": false,
  "status_code": 206,
  "step_time": 123,
  "context_id": "50dc3b5e-5841-4aa1-9f94-60cfb9aead79",
  "data": "aSDinaTvuI8gbWludGxpZnk="
}

Authorizations

Authorization

string

header

default:$CARTESIA_API_KEY

required

Cartesia API key (sk_car_...). Get one at play.cartesia.ai/keys.

Headers

Cartesia-Version

enum<string>

default:2026-03-01

required

API version header.

Available options:

2026-03-01

Example:

"2026-03-01"

Body

application/json

model_id

enum<string>

default:sonic-3.5

required

The ID of the model to use for the generation. See Models all options.

Available options:

sonic-3.5,

sonic-3,

sonic-preview,

sonic-latest

Example:

"sonic-3.5"

transcript

string

default:Hi there, it's awesome to meet you.

required

voice

TTSRequestVoiceSpecifier · object

required

Show child attributes

output_format

SSEOutputFormat · object

required

Show child attributes

language

string | null

Deprecated — use locale instead on Sonic 3.6 and later. The language the voice speaks the transcript in, as a code from the languages the model supports (en, hi). Supported languages are model-specific. See the language support section for the model you are calling — Sonic 3.6 or Sonic 3.5. Requesting a language a model does not support returns a 400 error; Odia (or), for example, is available on Sonic 3.6 but not on Sonic 3.5. Interchangeable with locale — set one or the other, never both. Setting both returns a 400 error, even if the values match. Existing integrations using language continue to work unchanged, including on Sonic 3.5 and earlier.

Example:

"en"

locale

string | null

The locale or language the voice speaks the transcript in, as a code from the supported locales or the languages the model supports (en-GB, hi-IN, en, hi). Accepts exactly the same values as language; set one or the other, never both. Setting both returns a 400 error, even if the values match. Locale codes such as en-GB require Sonic 3.6 or later; passing one to an earlier model returns a 400 error. Bare language codes such as en are accepted by every model that supports the field, in either locale or language. Supported languages and locales are model-specific. See the language support section for the model you are calling — Sonic 3.6 or Sonic 3.5. Locale codes are case-sensitive. Values not on the supported list return a 400 error — arbitrary BCP-47 codes are rejected, not ignored. See Text Normalization.

Example:

"en-GB"

normalization

string | null

default:auto

Controls how written forms (dates, times, numbers) are converted to spoken forms, independently of the voice's accent. One of auto (default), off, or a locale code from the supported locales (e.g. en-IN). Values not on the list return a 400 error. off disables only the automatic normalizer; SSML tags, generation controls, and pronunciation dictionaries still apply, and blocked characters still return a 400 error with their positions. Locale codes require Sonic 3.6 or later. See Text Normalization.

Example:

"auto"

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; not available on earlier models.

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

Show child attributes

speed

enum<string>

default:normal

deprecated

This property is deprecated and may not work for all voices. Use generation_config.speed instead. Influences the speed of the generated speech.

Available options:

slow,

normal,

fast

context_id

string | null

This can be any string value you find useful. The server will echo back the same context_id in events that it sends.

Contexts on the TTS (WebSocket) endpoint are used for continuations. > The TTS (SSE) endpoint does not support continuations, so most users just ignore this property.

Response

200 - text/event-stream

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

TTSSSEChunkEvent
TTSSSETimestampsEvent
TTSSSEPhonemeTimestampsEvent
TTSSSEDoneEvent
TTSSSEErrorEvent

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.

⌘I