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

# Quickstart

> Install the Creem Better Auth plugin and create an authenticated checkout.

This guide uses subscription persistence, the recommended setup for most applications. It stores
Creem customer and subscription identifiers in your Better Auth database and keeps them current
through webhooks.

## 1. Install the plugin

<CodeGroup>
  ```bash npm theme={null}
  npm install @creem_io/better-auth better-auth
  ```

  ```bash pnpm theme={null}
  pnpm add @creem_io/better-auth better-auth
  ```

  ```bash yarn theme={null}
  yarn add @creem_io/better-auth better-auth
  ```

  ```bash bun theme={null}
  bun add @creem_io/better-auth better-auth
  ```
</CodeGroup>

The Creem TypeScript SDK is included as a dependency of the plugin.

## 2. Configure the server plugin

Add your test API key and a webhook signing secret to the server environment:

```bash .env theme={null}
CREEM_API_KEY=creem_test_...
CREEM_WEBHOOK_SECRET=whsec_...
```

Register the plugin in your Better Auth configuration:

```typescript lib/auth.ts theme={null}
import { creem } from "@creem_io/better-auth";
import { betterAuth } from "better-auth";

export const auth = betterAuth({
  database: {
    // Your Better Auth database configuration
  },
  plugins: [
    creem({
      apiKey: process.env.CREEM_API_KEY!,
      webhookSecret: process.env.CREEM_WEBHOOK_SECRET!,
      testMode: true,
      defaultSuccessUrl: "/billing/success",
      persistSubscriptions: true,
    }),
  ],
});
```

The webhook endpoint is registered only when `webhookSecret` is present.

## 3. Generate the database schema

The plugin adds `creemCustomerId` and `hadTrial` to the Better Auth user model and creates a
`creem_subscription` model. With Better Auth's built-in Kysely adapter, apply the schema directly:

```bash theme={null}
npx @better-auth/cli migrate
```

When Prisma, Drizzle, or another ORM owns your schema, generate the schema instead and apply it with
that ORM's migration tooling:

```bash theme={null}
npx @better-auth/cli generate
```

See the
[Better Auth database documentation](https://www.better-auth.com/docs/concepts/database) when your
adapter requires manual migration steps.

## 4. Configure the client plugin

```typescript lib/auth-client.ts theme={null}
import { creemClient } from "@creem_io/better-auth/client";
import { createAuthClient } from "better-auth/react";

export const authClient = createAuthClient({
  plugins: [creemClient()],
});
```

If client and server are separate applications, install `@creem_io/better-auth` in both.

## 5. Create a checkout

The signed-in user's email is used when no customer is supplied. Their Better Auth user ID is added
to checkout metadata as `referenceId`.

```tsx app/pricing/subscribe-button.tsx theme={null}
"use client";

import { authClient } from "@/lib/auth-client";

export function SubscribeButton({ productId }: { productId: string }) {
  const subscribe = async () => {
    const { data, error } = await authClient.creem.createCheckout({
      productId,
      successUrl: "/billing/success",
    });

    if (error) {
      throw new Error(error.message);
    }

    if (data?.url) {
      window.location.assign(data.url);
    }
  };

  return <button onClick={subscribe}>Subscribe</button>;
}
```

## 6. Register the webhook

In the Creem dashboard, point a test-mode webhook at:

```text theme={null}
https://your-domain.com/api/auth/creem/webhook
```

`/api/auth` is Better Auth's default base path. Use your configured base path if you changed it.
For local development, expose the application over HTTPS with a tunnel and register that URL.

Once Creem delivers subscription events, the plugin updates the local subscription record. You can
also add [access callbacks](/code/sdks/better-auth/webhooks) for application-specific provisioning.

## Continue

<CardGroup cols={2}>
  <Card title="Configuration" href="/code/sdks/better-auth/configuration">
    Review every plugin option and persistence behavior.
  </Card>

  <Card title="Client API" href="/code/sdks/better-auth/client">
    Add the portal, cancellation, access checks, and transaction history.
  </Card>
</CardGroup>