Documentation

Next.js server actions guide

Read the visitor id in the browser (attribution().ml_visitor_id from the browser package, or the ml_vid cookie) and pass it into a Server Action. Take the price from your catalog on the server. A Server Action is a public POST, so authenticate the shopper and ignore any amount sent by the browser.

@analyticfast/node is not published. Vendor packages/node/src/index.ts until it is. Keep ANALYTICFAST_TOKEN in the server environment, never in a client component.

'use server';
import { createClient } from '@analyticfast/node';

const analytics = createClient({
  token: process.env.ANALYTICFAST_TOKEN!,
  baseUrl: process.env.ANALYTICFAST_BASE_URL!,
  siteId: process.env.ANALYTICFAST_SITE_ID,
});

export async function recordPaidOrder(input: { orderId: string; visitorId?: string }) {
  const order = await loadOrderForCurrentUser(input.orderId); // your database, not the client price
  return analytics.payment({
    transactionId: order.id,
    amountMinor: order.totalMinor, // 2999 = $29.99
    currency: order.currency,      // 'USD'
    visitorId: input.visitorId,
  });
}

Call it from the client with startTransition or a form action. Retrying the action with the same order id is safe. Use track (events:write) for a server-side goal such as signup, and identify only with identity the customer gave you.

The browser install stays the client component in [Next.js installation](../install/nextjs.md). Do not put the API token next to init().

Official references, checked 2026-10-26: use server, Server Actions.