Headless checkout SDK

The Headless Checkout SDK is for merchants who want a fully custom checkout page on their own domain. You own the layout, fields, and buyer experience. Shoppex still creates the invoice, starts the payment session, handles 3DS or redirects, receives webhooks, and fulfills the order. Use this when the hosted checkout page or modal embed is not flexible enough.

Headless checkout requires an active Business plan.

What you need

A storefront or app page on your own domain.
An active Business plan.
A headless checkout publishable key from the dashboard.
At least one allowed origin for the site that will call the browser API.
@shoppexio/checkout-js installed in your frontend app.

Dashboard setup

Open Dashboard -> Settings -> Developer -> Headless Checkout.

Generate a publishable key

Click Generate key. Copy the pk_live_... key immediately. The full key is shown only once.

Add your storefront origin

Add the exact origin that hosts your checkout page, for example https://yourstore.com.

Add local development origins

For local testing, add the exact local origin too, for example http://localhost:3000.

An origin is only the scheme, host, and optional port. Do not include a path.

URL you paste	Saved origin
`https://vyy.gg/checkout`	`https://vyy.gg`
`https://www.vyy.gg`	`https://www.vyy.gg`
`http://localhost:3000/cart`	`http://localhost:3000`

If your site works on both https://vyy.gg and https://www.vyy.gg, add both origins.

Never put a secret shx_... API key in browser code. Headless checkout uses pk_live_... or pk_test_... publishable keys only.

Install

npm install @shoppexio/checkout-js
# or
bun add @shoppexio/checkout-js

React example

import {
  ShoppexCheckoutProvider,
  useCheckoutSession,
  useStripePaymentSession,
  ShoppexPoweredBy,
} from '@shoppexio/checkout-js/headless/react';

function CheckoutForm() {
  const { session, loading, error } = useCheckoutSession({
    product_id: 'PROD_123',
    email: '[email protected]',
    quantity: 1,
  });

  const stripe = useStripePaymentSession(session?.id, {
    returnUrl: 'https://yourstore.com/thanks',
  });

  if (loading) return <p>Preparing checkout...</p>;
  if (error) return <p>{error.message}</p>;
  if (!session) return null;

  return (
    <form
      onSubmit={(event) => {
        event.preventDefault();
        void stripe.confirm();
      }}
    >
      <h1>{session.product?.title ?? 'Checkout'}</h1>
      <p>Total: {session.breakdown.total} {session.currency}</p>

      <div ref={stripe.mountRef} />

      <button type="submit" disabled={!stripe.ready}>
        Pay now
      </button>

      <ShoppexPoweredBy />
    </form>
  );
}

export default function Page() {
  return (
    <ShoppexCheckoutProvider publishableKey="pk_live_your_key_here">
      <CheckoutForm />
    </ShoppexCheckoutProvider>
  );
}

ShoppexPoweredBy is currently required for every Headless Checkout. The SDK checks that the badge is visible before payment confirmation. The server owns this directive; the browser cannot disable it.

API shape

The browser SDK sends the publishable key in the x-shoppex-publishable-key header. Shoppex also checks the request Origin header against your allowed origins. The SDK can:

create a checkout session
read the current session status
apply or remove coupons
set tips
select add-ons
save buyer email, marketing preference, billing address, and method-specific terms acceptance
save product custom fields and delivery instructions
start a gateway payment session
complete zero-total checkouts
request and verify Customer Balance OTPs, then apply full or partial balance payments
submit browser-bound proof for manual payment methods
capture/finalize PayPal and SumUp payments
fetch delivery after the payment is complete

The session response includes line items, totals, authoritative gateway fee previews, payment-method presentation and requirements, buyer identity state, Customer Balance availability, product custom-field definitions, delivery instructions, shop branding, terms, and delivery state. Render against the gateway kind, not the provider name, so your UI works across card, redirect, crypto, balance, and manual payment flows.

Buyer details and payment requirements

Each entry in session.gateways_available contains:

fee_preview: the server-calculated fee for that method
presentation: merchant label, button label, icon, and provider-attribution preference
requirements: whether method terms and a billing address must be saved

presentation.hide_provider_attribution only controls the payment provider’s attribution. It does not remove the required ShoppexPoweredBy badge. Persist the details before starting the gateway:

await client.updateSession(session.id, {
  email: '[email protected]',
  payment_method_terms_accepted: true,
  billing_address: {
    name: 'Customer Name',
    line1: '1 Main Street',
    city: 'Berlin',
    country: 'DE',
    postal_code: '10115',
  },
  custom_fields: {
    line_item_id: { discord_username: 'customer' },
  },
  delivery_instructions: {
    line_item_id: 'Send to customer on Discord',
  },
});

Free and Customer Balance checkout

if (!session.payment_required) {
  await client.completeFreeCheckout(session.id);
}

await client.requestBalanceOtp(session.id, '[email protected]');
const verified = await client.verifyBalanceOtp(
  session.id,
  '[email protected]',
  '123456',
);
await client.payWithBalance(session.id, verified.session_token);

Customer Balance uses the same wallet, policy, attempt, reconciliation, stock-hold, and completion-access services as Hosted Checkout.

Crypto progress and underpayments

Call getSession() or the React refresh() action to read the authoritative payment projection. session.payment_detail includes the exact decimal strings needed for a crypto progress or underpayment UI:

const detail = session.payment_detail;

if (typeof detail?.confirmations_needed === 'number') {
  console.log(`${detail.confirmations ?? 0}/${detail.confirmations_needed}`);
}

if (detail?.remaining && detail.buyer_actionable !== false) {
  console.log(`Send ${detail.remaining} ${detail.crypto_currency ?? 'crypto'}`);
}

if (detail?.buyer_actionable === false) {
  console.log(detail.buyer_action_reason);
}

if (detail?.received && detail.received_fiat_estimate) {
  console.log(
    `Received on-chain: ${detail.received} ${detail.crypto_currency} (~${detail.received_fiat_estimate} ${detail.fiat_currency})`,
  );
  console.log(`Credited by provider: ${detail.credited_fiat ?? '0'} ${detail.fiat_currency}`);
}

The detail contains expected, received, remaining, crypto_currency, buyer_actionable, buyer_action_reason, provider_status, credited_fiat, received_fiat_estimate, fiat_currency, confirmations, and confirmations_needed when those values are available. credited_fiat is the amount the provider applied to the invoice. received_fiat_estimate is only a display estimate for crypto observed on-chain and must never be counted as paid. Keep the amount values as strings. Do not recalculate the remainder with JavaScript floating-point numbers.

Embed provider adapters

Stripe uses useStripePaymentSession. The framework-agnostic Headless export also includes:

import {
  mountSquareCard,
  mountNmiCardFields,
  mountSumupCard,
  mountPaypalButtons,
} from '@shoppexio/checkout-js/headless';

These helpers mount provider-owned fields into your element and call the same Shoppex session/finalize endpoints as Hosted Checkout. Square and NMI perform their tokenized second session call; SumUp finalizes after the widget succeeds; PayPal captures the approved order. NMI includes Kount and 3D Secure when the merchant gateway requires them.

Manual payment proof

When a manual payment session has require_proof: true, use proof_type to render a note input, image input, or both. Then submit the proof with the completion grant returned by the start call:

await client.submitManualProof(session.id, start.completion_access_grant, {
  customer_note: 'Bank transfer sent',
  image: proofFile,
});

The SDK registers completion access before uploading. A publishable key alone cannot submit proof for another buyer’s invoice.

Troubleshooting

Generate key fails

Check these first:

The shop has an active Business plan.
You are using the shop owner account or a team member with permission to manage webhooks/developer settings.
Your dashboard session is fresh. Refresh the page or log out and back in.

If it still fails, open browser DevTools -> Network and inspect:

POST /v1/dashboard/checkout/headless/rotate-key

Common responses:

Status	Meaning
`403 BUSINESS_PLAN_REQUIRED`	The shop is not on an active Business plan.
`401`	The dashboard session or shop permission is invalid.
`500`	Backend or database issue. Contact support with the request id if available.

Add origin fails

Use a full http:// or https:// origin. These are valid:

https://vyy.gg
https://www.vyy.gg
http://localhost:3000

These are not valid saved origins:

vyy.gg
https://vyy.gg/checkout
ftp://vyy.gg

The dashboard normalizes paths away before saving, but the backend still rejects non-http origins and malformed values. If the UI only shows a generic error, inspect this request:

PUT /v1/dashboard/checkout/headless/origins

Browser API calls fail

Check the browser response code:

Status	Meaning
`401`	Missing, malformed, or unknown publishable key. Make sure it starts with `pk_live_` or `pk_test_`.
`403 ORIGIN_NOT_ALLOWED`	The calling site’s origin is not in the allowed origins list.
`403 BUSINESS_PLAN_REQUIRED`	Headless checkout is not enabled for the shop’s current plan.

Headless Commerce Overview

Pick the right integration shape for custom storefronts, apps, and backend flows.

Checkout Embed SDK

Use the hosted modal when you do not need a fully custom checkout UI.

Storefront SDK

Read public product, cart, and storefront data from browser code.

Webhooks

Fulfill orders and update your app after Shoppex receives payment events.

Start here

Invoices and payments

Webhooks

Headless commerce

Storefront SDK

Checkout embeds

Integrations

Resellers

Email marketing

Tutorials

Headless checkout SDK

What you need

Dashboard setup

Install

React example

API shape

Buyer details and payment requirements

Free and Customer Balance checkout

Crypto progress and underpayments

Embed provider adapters

Manual payment proof

Troubleshooting

Generate key fails

Add origin fails

Browser API calls fail

Headless Commerce Overview

Checkout Embed SDK

Storefront SDK

Webhooks

​What you need

​Dashboard setup

​Install

​React example

​API shape

​Buyer details and payment requirements

​Free and Customer Balance checkout

​Crypto progress and underpayments

​Embed provider adapters

​Manual payment proof

​Troubleshooting

​Generate key fails

​Add origin fails

​Browser API calls fail

​Related docs

Headless Commerce Overview

Checkout Embed SDK

Storefront SDK

Webhooks

What you need

Dashboard setup

Install

React example

API shape

Buyer details and payment requirements

Free and Customer Balance checkout

Crypto progress and underpayments

Embed provider adapters

Manual payment proof

Troubleshooting

Generate key fails

Add origin fails

Browser API calls fail

Related docs