Attribute revenue with custom payment providers

If you already use a connected provider such as Stripe, Paddle, LemonSqueezy, or Polar, prefer that built-in integration first.

Choose the right API credential

For most custom payment-provider integrations, use a website API key from the website's Settings > API page. Website keys start with flow_ and are already scoped to that one website.

Use a workspace API token from the workspace API Tokens page only when a shared backend, MCP integration, or automation needs access to multiple websites. Workspace tokens start with flow_ws_. When you use one, include websiteId or domain in the request body so Flowsery knows which website should receive the payment.

Send payments with the current API contract

When a payment succeeds, call the Flowsery Payment API:

JavaScript

await fetch('https://analytics.flowsery.com/api/v1/payments', {
  method: 'POST',
  headers: {
    Authorization: `Bearer ${FLOWSERY_API_KEY}`,
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    // Required only when FLOWSERY_API_KEY is a workspace token.
    websiteId: process.env.FLOWSERY_WEBSITE_ID,
    amount: 29.99,
    currency: 'USD',
    transactionId: 'txn_98hj',
    visitorUid: request.cookies._fs_vid,
    sessionUid: request.cookies._fs_sid,
    email: 'buyer@example.com',
    name: 'Buyer Name',
    customerId: 'cus_123',
  }),
});

Notes

Use the backend field names exactly: visitorUid, sessionUid, and transactionId.
websiteId or domain is required for flow_ws_ workspace tokens and optional for flow_ website API keys.
amount should always be sent.
Deduplication is based on transactionId.
Refunds should reuse the original transactionId and set isRefund: true.

For the endpoint details, see Create Payment.