Attribute revenue with LemonSqueezy Checkout API

Before proceeding, confirm that you have linked your LemonSqueezy account.

Include custom with _fs_vid and _fs_sid (cookies set by Flowsery Analytics) when creating a checkout session:

// 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: {
          _fs_vid: cookieStore.get('_fs_vid')?.value,
          _fs_sid: cookieStore.get('_fs_sid')?.value
        }
      }
    }
  });
}

Once connected and custom data is passed correctly, Flowsery Analytics will automatically attribute revenue to the appropriate marketing channels. No webhook configuration is needed.

Following a successful payment, revenue data should appear in your dashboard (referrer, country, browser, etc.).