> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://docs.vapi.ai/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://docs.vapi.ai/_mcp/server.

# Cartesia

> Use a custom Cartesia voice in Vapi by connecting your Cartesia API key and selecting your voice.

This guide shows you how to use a voice you created with Cartesia in your Vapi assistant. Cartesia's prebuilt voices are already available in the [Voice Library](/providers/voice/overview); follow this page only to use your own custom voice.

> **Note**
>
> A Cartesia account and API key are required for this process.

#### Create a Cartesia account and voice

Sign up at [Cartesia](https://play.cartesia.ai), then create a custom voice in the [Cartesia playground](https://play.cartesia.ai/voices). Note that you will need to set the access of the voice to public in Cartesia to use it in Vapi. [Check their docs](https://docs.cartesia.ai/build-with-cartesia/capability-guides/choosing-a-voice#sharing-a-voice) for more information.

#### Retrieve your Cartesia API key

Get your API key from your Cartesia account.

#### Enter your API key in Vapi

In the [Vapi Dashboard](https://dashboard.vapi.ai), open **Settings**, then **Integrations**, and add your Cartesia API key under **Cartesia**.

Once you save, your Cartesia voices sync automatically.

#### Select your custom voice

Open an assistant and open **Voice Settings**. Choose **Cartesia** as the provider and select your voice, or switch to **Custom Voice ID** and paste your Cartesia voice ID. You can find your voice ID in the [Voice Library](/providers/voice/overview).