> ## Documentation Index
> Fetch the complete documentation index at: https://docs.custral.com/llms.txt
> Use this file to discover all available pages before exploring further.

# SDKs

> Official Custral client libraries.

Custral publishes official client libraries on npm. Pick the one that matches where your code runs and which key you hold:

<CardGroup cols={2}>
  <Card title="TypeScript SDK" icon="js" href="/dev/sdks/typescript">
    **`@custral/sdk`**: the server-side, **secret-key** (`sk_…`) client for the `/v1` REST API. Records, objects, identity, usage modules, MCP introspection, and webhook verification.
  </Card>

  <Card title="Browser SDK" icon="browser" href="/dev/sdks/browser">
    **`@custral/js`**: the browser, **publishable-key** (`pk_…`) layer. `CustralUsage` for metering, one error hierarchy, and the realtime connector.
  </Card>

  <Card title="React SDK" icon="react" href="/dev/sdks/react">
    **`@custral/widget`**: the chat widget as a React component, plus the headless engine underneath it. Builds on `@custral/js`.
  </Card>
</CardGroup>

## Which one?

|         | `@custral/sdk`                  | `@custral/js`                    | `@custral/widget`  |
| ------- | ------------------------------- | -------------------------------- | ------------------ |
| Runs    | Server (Node / Bun)             | Browser                          | Browser (React)    |
| Key     | Secret `sk_…`                   | Publishable `pk_…`               | Publishable `pk_…` |
| Surface | Records, objects, webhooks, MCP | Usage tracking, errors, realtime | Chat widget        |

There's also the [`@custral/cli`](/dev/cli/overview) for working with your workspace from the terminal as yourself, and the [`widget.js`](/comms/chat/widget-install) drop-in script for embedding chat with no bundler.

<Note>
  **`@custral/ui` is deprecated.** It never contained any UI: it shipped the chat
  engine and the usage client. Those are now `@custral/widget` and
  `@custral/js`. The APIs are unchanged, so migrating is a rename of the import.
</Note>

## Roadmap

* Python and Ruby SDKs.
* A workflow-action SDK for hosted custom actions.


## Related topics

- [Developer Overview](/dev/overview.md)
- [Getting Started](/dev/getting-started.md)
- [Browser SDK](/dev/sdks/browser.md)
- [React SDK](/dev/sdks/react.md)
- [TypeScript SDK](/dev/sdks/typescript.md)