Seamless SDK (Payment Web)

Follow this step-by-step guide to implement and enable Yuno’s Seamless Web SDK payment functionality in your application.

Recommended SDKWe recommend using the Web Seamless SDK for a smooth integration experience. This option provides a flexible payment solution with pre-built UI components and customization options.

Should I use Lite or Full Seamless SDK?Use the Full Seamless SDK for automatic payment method listing and separate display of payment buttons (like PayPal). The Lite Seamless SDK gives you more control over how payment methods are displayed and organized.

Step 1: Include the library in your project

The integration guide provides three flexible methods:

Direct HTML script inclusion
Dynamic JavaScript injection
NPM module installation

Choose the integration method that best suits your development workflow and technical requirements. After completing the SDK integration, you can proceed with the following steps to implement the Seamless functionality.

TypeScript LibraryIf you are using TypeScript, Yuno offers a library that provides access to all available methods in the Yuno Web SDK.

Step 2: Initialize SDK with the public key

Initialize the Yuno SDK in your JavaScript application by providing a valid PUBLIC_API_KEY:

const yuno = await Yuno.initialize(PUBLIC_API_KEY);

CredentialsSee the credentials page for more information: Authentication

Step 3: Create a checkout session

If your workflow requires sending the additional_data object, it can be sent as part of the checkout session.

To initialize the payment flow, create a new checkout_session using the Create checkout session endpoint.

First, create a customer or retrieve an existing customer ID
Include it when creating the checkout_session

To control authorization and capture with cards, include payment_method.detail.card.capture in the checkout session: set false to authorize only, true to capture immediately.

Key parameters

Parameter	Required	Description
`amount`	Yes	The primary transaction amount object containing `currency` (ISO 4217 code) and `value` (numeric amount in that currency).
`alternative_amount`	No	An alternative currency representation of the transaction amount with the same structure as `amount` (`currency` and `value`). Useful for multi-currency scenarios, such as displaying prices to customers in their preferred currency (e.g., USD) while processing the payment in the local currency (e.g., COP).

onPaymentMethodSelect EventFor all APMs, including Google Pay, Apple Pay, and PayPal, onPaymentMethodSelected is triggered as soon as the customer chooses the payment method (before the payment flow begins). Define onPaymentMethodSelected in startSeamlessCheckout before mountSeamlessCheckout.

Google Pay and Apple Pay DisplayFrom SDK version 1.5, Google Pay and Apple Pay appear as direct buttons instead of radio buttons in the payment methods list. They are displayed separately from other payment methods.

Step 4: Start the checkout process

Use the configuration below to provide a seamless and user-friendly payment experience for your customers:

await yuno.startSeamlessCheckout({
  checkoutSession: "438413b7-4921-41e4-b8f3-28a5a0141638",
  elementSelector: "#root",
  countryCode: "US",
  language: "en-US",
  showLoading: true,
  issuersFormEnable: true,
  showPaymentStatus: true,
  onLoading: (args) => console.log(args),
  renderMode: {
    type: "modal",
    elementSelector: {
      apmForm: "#form-element",
      actionForm: "#action-form-element",
    },
  },
  card: {
    type: "extends",
    styles: "",
    cardSaveEnable: false,
    texts: {},
    hideCardholderName: false, // Optional: Set to true to hide cardholder name field
  },
  texts: {},
  async yunoCreatePayment(oneTimeToken, tokenWithInformation) {
    await createPayment({ 
      oneTimeToken, 
      checkoutSession,
      vault_on_success: true 
    });
    await yuno.continuePayment({ showPaymentStatus: true });
  },
  onPaymentMethodSelected(data) {
    console.log("Payment method selected:", data);
  },
  yunoPaymentResult(data) {
    console.log("Payment result:", data);
    await yuno.hideLoader();
  },
  yunoError(error, data) {
    console.error("An error occurred:", error);
    await yuno.hideLoader();
  },
});

When using startSeamlessCheckout, specify the callbacks to handle payments. You can also customize the checkout interface using the texts objects.

Parameters

Configure the seamless checkout with the following options:

Parameter	Description
`checkoutSession`	Refers to the current payment’s checkout session. Example: `438413b7-4921-41e4-b8f3-28a5a0141638`.
`elementSelector`	The HTML element where the checkout will be rendered.
`countryCode`	This parameter specifies the country for which the payment process is being set up. Use an `ENUM` value representing the desired country code. You can find the full list of supported countries and their corresponding codes on the Country Coverage page.
`language`	Language for payment forms. Use any code listed in Supported languages. Example: `en-US`. Defaults to browser language when available.
`showLoading`	Controls the visibility of the Yuno loading/spinner page during the payment process. Default: `true`.
`onLoading`	Required to receive notifications about server calls or loading events during the payment process.
`issuersFormEnable`	Enables the issuer’s form (e.g., a list of banks). Default: `true`.
`showPaymentStatus`	Shows the Yuno Payment Status page, which is useful when continuing a payment. Default: `true`.
`showPayButton`	Controls the visibility of the pay button in the customer or card form. Default: `true`.
`renderMode`	Specify how and where the forms will be rendered. The options available are:
	▪️ `type: modal` (default)
	▪️ `type: element` - If you select `element`, you must inform the `elementSelector` to specify where the form should be rendered.
`card`	Defines the configuration for the card form. It contains settings like custom styles, save card option, and optional `hideCardholderName` to hide the cardholder name field. When `hideCardholderName` is set to `true`, the cardholder name field is not rendered. When not specified or set to `false`, the cardholder name field is displayed (default behavior). Hiding the field does not affect PAN, expiry, CVV collection, BIN logic, or 3DS/provider validations.
`texts`	Allows you to set custom button texts for card and non-card payment forms.
`yunoCreatePayment`	Placeholder function for creating a payment. This function will not be called but should be implemented. When creating the payment, you can include `vault_on_success: true` to enroll the payment method after a successful payment. See Enrolling payment methods for more details.
`onPaymentMethodSelected`	Callback invoked when a payment method is selected, along with the method’s type and name.
`yunoPaymentResult`	Callback called after the payment is completed, with the payment status (e.g., `SUCCEEDED`, `ERROR`, `CANCELED_BY_USER`).
`yunoError`	Callback invoked when there is an error in the payment process. Receives error type and optional additional data.

Customer and Merchant-Initiated TransactionsPayments can be initiated by the customer (CIT) or by the merchant (MIT). You find more information about their characteristics in Stored credentials.The step-by-step on this page refers to a customer-initiated transaction without the recurrence option. Typically, it’s used in one-time online purchases, in-store purchases, ATM withdrawals, etc.

Step 5: Mount the SDK

To present the checkout process based on the selected payment method, use the await yuno.mountSeamlessCheckout() function. This step ensures the SDK is properly mounted on your chosen HTML element.

await yuno.mountSeamlessCheckout({
  paymentMethodType: PAYMENT_METHOD_TYPE,
  vaultedToken: VAULTED_TOKEN,
});

See the Payment type page to view the complete list of payment method types you can use when mounting the SDK. The vaultedToken is optional. It represents a previously enrolled payment method. If you provide the vaultedToken, the user will not be required to provide the payment information again since it was provided in a previous transaction. After mounting, you must start the checkout flow by calling await yuno.startPayment(). If you skip this call, the payment form will not open.

Step 6: Start the payment flow (Required)

Call await yuno.startPayment() immediately after await yuno.mountSeamlessCheckout() to open the selected payment method UI:

await yuno.mountSeamlessCheckout({
  paymentMethodType: PAYMENT_METHOD_TYPE,
  vaultedToken: VAULTED_TOKEN,
});

await yuno.startPayment();

Alternatively, you can trigger the start from a user action such as a button click:

const payButton = document.querySelector('#button-pay');
payButton.addEventListener('click', async () => {
  await yuno.startPayment();
});

Demo AppIn addition to the code examples provided, you can access the Demo App for a complete implementation of Yuno SDKs (clone from the repository).

Mount external buttons

You can use the mountExternalButtons method to render Google Pay and Apple Pay buttons in custom locations within your UI. This gives you control over where these buttons are displayed.

await yuno.mountExternalButtons([
  {
    paymentMethodType: 'APPLE_PAY',
    elementSelector: '#apple-pay',
  },
  {
    paymentMethodType: 'GOOGLE_PAY',
    elementSelector: '#google-pay',
  },
]);

Parameters

Parameter	Description
`paymentMethodType`	The payment method type. Must be either `'APPLE_PAY'` or `'GOOGLE_PAY'`.
`elementSelector`	The CSS selector for the HTML element where the button should be rendered (e.g., `'#apple-pay'`, `'.button'`).

Unmounting buttons

You can unmount a single external button by payment method type:

await yuno.unmountExternalButton('APPLE_PAY');

Or unmount all external buttons at once:

await yuno.unmountAllExternalButtons();

Unmounting the SDK

For explicit cleanup of the Yuno SDK (e.g., when a user cancels the flow or you need to remove the SDK from the DOM), use the unmountSdk() method:

await yuno.unmountSdk();

Revolut Pay

There are two ways to render the Revolut Pay button:

Full checkout — the button shows up inside the payment method list rendered by the SDK.
External buttons (mountExternalButtons) — the merchant decides which container on their page the button mounts into.

In both cases, the button configuration goes in externalButtons.revolutPay inside startCheckout. Unlike other buttons, the widget is rendered by Revolut’s own SDK — the configuration maps directly to Revolut’s button options.

External buttons integration

The merchant defines a container in their HTML and mounts the button there:

<div id="revolut-pay-element"></div>

const yuno = await window.Yuno.initialize(PUBLIC_API_KEY);

await yuno.startCheckout({
  checkoutSession,
  elementSelector: '#root',
  countryCode,
  language,

  // Receives the one-time token when the buyer confirms in the Revolut widget.
  // IMPORTANT: create the payment in your backend RIGHT AWAY and call
  // continuePayment() — the Revolut widget stays open waiting for the order
  // to be completed with the created payment.
  async yunoCreatePayment(oneTimeToken, tokenWithInformation) {
    await createPaymentInYourBackend({ oneTimeToken, checkoutSession });
    yuno.continuePayment();
  },

  yunoPaymentResult(data) { /* final payment status */ },
  yunoError: (error) => { /* flow errors (including widget cancellation) */ },

  // Receives { isLoading, type } — Revolut Pay emits type: 'OTT' while the
  // token is generated and type: 'CREATE_PAYMENT' in the SDK-driven flow.
  onLoading: (data) => { /* show/hide your loader */ },

  // Button configuration (see Configuration section below)
  externalButtons: {
    revolutPay: {
      variant: 'dark',
      size: 'large',
      radius: 'round',
      action: 'pay',
      locale: 'es',
    },
  },
});

await yuno.mountExternalButtons([
  {
    paymentMethodType: 'REVOLUT_PAY',
    elementSelector: '#revolut-pay-element',
  },
]);

To unmount the Revolut Pay button, use the same methods described in Unmounting buttons:

yuno.unmountExternalButton('REVOLUT_PAY'); // this button only
yuno.unmountAllExternalButtons(); // all external buttons

Checkout session requirements

For Revolut Pay to work, the checkout session the merchant creates (backend to backend) must include these fields — the SDK reads them from the session, nothing is configured on the frontend:

amount.value and amount.currency — required; used to create the Revolut order shown in the widget.
callback_url — required; used as the mobile redirect URL to return to the merchant page (see Mobile redirects below).

Configuration (`externalButtons.revolutPay`)

All configuration is optional. The button is rendered by Revolut, so the options map to Revolut’s official button styles:

Option	Values	Default	What it does
`variant`	`'dark'` \| `'light'` \| `'light-outlined'`	Revolut decides	Button color scheme
`size`	`'large'` \| `'small'`	`'large'` (full-width)	Button size (`small` renders inline)
`radius`	`'none'` \| `'small'` \| `'large'` \| `'round'`	Revolut decides	Corner radius (`none` 0px / `small` 4px / `large` 16px / `round` pill)
`action`	`'pay'` \| `'buy'` \| `'donate'` \| `'subscribe'`	`'pay'`	Button label
`locale`	ISO locale (e.g. `'en'`, `'es'`, `'pt-BR'`) or `'auto'`	`'auto'`	Button language. Invalid values fall back to `'auto'`

Mobile redirects (`callback_url`)

On mobile, the Revolut flow can jump to the Revolut app (or an in-app browser) instead of staying in the popup. To come back to the merchant’s page, the SDK needs redirect URLs — it resolves them automatically from the callback_url the merchant already sends when creating the checkout session (backend to backend):

The session’s callback_url is used for the three outcomes: success, failure, and cancel.
Nothing extra is needed in the SDK configuration — if the session has a callback_url, mobile redirects work; if it doesn’t, the flow stays web-only.
When the buyer returns from the Revolut app, the URL includes a _rp_fr query parameter appended by Revolut — harmless, but merchants parsing the return URL strictly should be aware of it.

Desktop vs. mobile redirectsOnly mobile redirect URLs are configured by the SDK. Desktop flows always resolve inside the widget/popup — no redirect happens.

PayPal REDIRECT Workflow

The Yuno SDK supports a REDIRECT workflow for PayPal. This workflow is useful when PayPal was not initialized at the start of the SDK or when using a pre-existing PayPal orderId.

PaypalButtonModal: If PayPal is not initialized, the SDK can render the PayPal button inside a modal.
Workflow: The REDIRECT workflow skips fraud detection and OTT creation, utilizing the provided orderId.

// Example PayPal configuration
await yuno.startSeamlessCheckout({
  // ... other config
  paypal: {
    workflow: 'REDIRECT',
    orderId: 'PAYPAL_ORDER_ID',
  }
});

Enrolling payment methods in seamless flow

You can enroll payment methods (store cards for future use) directly during the seamless payment flow by setting payment_method.vault_on_success = true in the checkout session creation. When vault_on_success is set to true:

The payment method will be automatically enrolled if the payment status is SUCCEEDED
If the payment does not succeed, no vaulting will occur
The payment response will include a vaulted_token that you can use for future transactions

Example:

{
    "account_id": "...",
    ...
    "payment_method": {
        "vault_on_success": true
    }
}

Vaulting RequirementsTo generate and receive a vaulted_token when vault_on_success = true, the payment must reference an existing Yuno customer through customer_payer.id in the checkout session. Creating or sending the customer data inline inside the payment request does not create the customer on our side, so no vaulting will occur.

For more information about enrolling payment methods, see Enroll Payment Methods.

Error handling

Handle errors returned by the SDK in your app (e.g. failed payments, validation errors). For HTTP status and response codes, see Status and response codes in the API reference.

Payment retry

When a card payment comes back DECLINED or ERROR, payment retry keeps the card form open so the shopper can correct their details and try again without restarting checkout — controlled by settings.card.enable_payment_retry under styling.settings. In the seamless flow this is automatic — the SDK keeps the form open and drives the retry for you. In the Full Checkout, Lite, and Secure Fields flows you must call continuePayment on a declined/errored card payment to trigger it. See Payment retry in the Web Reference for details.

Stay updated

Visit the changelog for the latest SDK updates and version history.

Overview

Seamless SDK

Lite SDK

Headless SDK

Customization

Card Enrollment

Resources

Additional Platforms

External Native Modules

Step 1: Include the library in your project

Step 2: Initialize SDK with the public key

Step 3: Create a checkout session

Key parameters

Step 4: Start the checkout process

Parameters

Step 5: Mount the SDK

Step 6: Start the payment flow (Required)

Mount external buttons

Parameters

Unmounting buttons

Unmounting the SDK

Revolut Pay

External buttons integration

Checkout session requirements

Configuration (`externalButtons.revolutPay`)

Mobile redirects (`callback_url`)

PayPal REDIRECT Workflow

Enrolling payment methods in seamless flow

Error handling

Payment retry

Stay updated

​Step 1: Include the library in your project

​Step 2: Initialize SDK with the public key

​Step 3: Create a checkout session

​Key parameters

​Step 4: Start the checkout process

​Parameters

​Step 5: Mount the SDK

​Step 6: Start the payment flow (Required)

​Mount external buttons

​Parameters

​Unmounting buttons

​Unmounting the SDK

​Revolut Pay

​External buttons integration

​Checkout session requirements

​Configuration (externalButtons.revolutPay)

​Mobile redirects (callback_url)

​PayPal REDIRECT Workflow

​Enrolling payment methods in seamless flow

​Error handling

​Payment retry

​Stay updated

Step 1: Include the library in your project

Step 2: Initialize SDK with the public key

Step 3: Create a checkout session

Key parameters

Step 4: Start the checkout process

Parameters

Step 5: Mount the SDK

Step 6: Start the payment flow (Required)

Mount external buttons

Parameters

Unmounting buttons

Unmounting the SDK

Revolut Pay

External buttons integration

Checkout session requirements

Configuration (`externalButtons.revolutPay`)

Mobile redirects (`callback_url`)

PayPal REDIRECT Workflow

Enrolling payment methods in seamless flow

Error handling

Payment retry

Stay updated