Cartesia API

by docs.cartesia.ai

Speech, image and audio Added on November 3rd, 2026 Checked and working on November 3rd, 2026

What it does

The Cartesia API offers fast text-to-speech and speech-to-text, for example to give a voice agent spoken answers. A POST request with a JSON body (model, transcript, voice, output format) returns WAV, MP3 or raw audio; SSE and WebSocket streaming are also available. Requests need an Authorization: Bearer and a Cartesia-Version header. Free plan with 20,000 credits per month (text-to-speech uses about one credit per character); a commercial use license comes with paid plans. An official MCP server at https://mcp.cartesia.ai/mcp lets AI agents generate speech, transcribe audio and manage voices.

API
JSON
MCP
REST

At a glance

API key: Needed, free · More APIs with a free key
Pricing: Free plan with 20,000 credits per month (text-to-speech uses about one credit per character); a commercial use license comes with paid plans.
Commercial use: Not on the free plan
From the browser: Yes (CORS)
Formats: JSON
Interface: REST, MCP
Provider: docs.cartesia.ai
Last checked: Working on November 3rd, 2026

More information: https://docs.cartesia.ai/api-reference/tts/bytes

Compare: ElevenLabs API vs Cartesia API

Is this your service? Show that it is listed

Put this badge on your website or in your README; it links to this page. About the badge

HTML

<a href="https://free-web-services.com/web-services/ai/media/cartesia-api.html"><img src="https://free-web-services.com/badge.svg" width="208" height="44" alt="Listed on Free Web Services" /></a>

Markdown

[![Listed on Free Web Services](https://free-web-services.com/badge.svg)](https://free-web-services.com/web-services/ai/media/cartesia-api.html)

Example request

curl

curl -X POST 'https://api.cartesia.ai/tts/bytes' \
  -H 'Authorization: Bearer YOUR_API_KEY' \
  -H 'Cartesia-Version: 2026-08-14' \
  -H 'Content-Type: application/json' \
  -d '{"model_id":"sonic-3","transcript":"Hello, world!","voice":{"mode":"id","id":"db6b0ed5-d5d3-463d-ae85-518a07d3c2b4"},"output_format":{"container":"mp3","sample_rate":44100,"bit_rate":128000}}'

JavaScript

const response = await fetch("https://api.cartesia.ai/tts/bytes", {
  method: 'POST',
  headers: {
    "Authorization": "Bearer YOUR_API_KEY",
    "Cartesia-Version": "2026-08-14",
    "Content-Type": "application/json",
  },
  body: JSON.stringify({"model_id":"sonic-3","transcript":"Hello, world!","voice":{"mode":"id","id":"db6b0ed5-d5d3-463d-ae85-518a07d3c2b4"},"output_format":{"container":"mp3","sample_rate":44100,"bit_rate":128000}}),
});
const data = await response.json();
console.log(data);

Python

import requests

response = requests.post(
    "https://api.cartesia.ai/tts/bytes",
    headers={
        "Authorization": "Bearer YOUR_API_KEY",
        "Cartesia-Version": "2026-08-14",
        "Content-Type": "application/json",
    },
    json={
        "model_id": "sonic-3",
        "transcript": "Hello, world!",
        "voice": {
            "mode": "id",
            "id": "db6b0ed5-d5d3-463d-ae85-518a07d3c2b4",
        },
        "output_format": {
            "container": "mp3",
            "sample_rate": 44100,
            "bit_rate": 128000,
        },
    },
    timeout=30,
)
print(response.json())

Replace YOUR_API_KEY with your own key. The JavaScript works in a web page as well as in Node.js 18 or newer.