Source: https://datafa.st/docs/lemonsqueezy-checkout-api
Markdown source: https://datafa.st/docs/lemonsqueezy-checkout-api.md
Description: Set up revenue attribution with LemonSqueezy Checkout API. Pass DataFast cookies as custom data for accurate marketing channel attribution.

# Attribute revenue with LemonSqueezy Checkout API

← [Revenue attribution guide](/docs/revenue-attribution-guide)

# Attribute revenue with LemonSqueezy Checkout API

> Make sure you've [connected your LemonSqueezy account](/docs/connect-payment-provider) first.

Pass `custom` with `datafast_visitor_id` and `datafast_session_id` (cookies from DataFast) when creating a checkout session:

```javascript
// app/api/create-checkout/route.js
import { cookies } from 'next/headers';

export async function POST() {
  const cookieStore = cookies();
  // If you're using Next.js 15+, use this instead:
  // const cookieStore = await cookies();
  
  const { data, error } = await createCheckout({
    storeId,
    variantId,
    {
      productOptions: { ... },
      checkoutData: {
        ...,
        custom: {
          datafast_visitor_id: cookieStore.get('datafast_visitor_id')?.value,
          datafast_session_id: cookieStore.get('datafast_session_id')?.value
        }
      }
    }
  });
}
```

Once connected and custom data is properly passed, DataFast will automatically attribute revenue to the correct marketing channels. **No webhook setup is required**.

> After receiving a successful payment, you should see revenue data in your dashboard (referrer, country, browser, etc.).