> ## Documentation Index > Fetch the complete documentation index at: https://primer.io/docs/llms.txt > Use this file to discover all available pages before exploring further. # showUniversalCheckout ```ts theme={"dark"} showUniversalCheckout( clientToken: string, options: UniversalCheckoutOptions ): Promise ``` Showing Drop-in Checkout is the simplest way to integrate with Primer. With just a few lines of code, you can display a fully in-context checkout UI with all your payment methods. Availing Drop-In Checkout is as easy as implementing one line of code. ```ts theme={"dark"} import { Primer } from "@primer-io/checkout-web"; const checkout = await Primer.showUniversalCheckout(clientToken, { container: "#container", onCheckoutComplete(...args) { console.log("onCheckoutComplete", ...args); }, }); ``` Note that there are more options which can be passed to Drop-In Checkout. Please refer to the section below for more information. ## Parameters **clientToken** `string` *required* A string containing a client token as returned by the Primer API when you [create a client session](https://primer.io/docs/checkout/client-session.md#create-a-client-session). **universalCheckoutOptions** `object` *required* When calling `showUniversalCheckout` you can provide Drop-In Checkout with some configuration options. These options range from callbacks notifying you of the current payment's status, to styling options for certain UI elements. **container** `string | Element` *required* The container element in which the checkout should be rendered. **locale** `string` This option forces the locale. By default, the locale will be set to the browser's locale. **merchantDomain** `string` Optional domain override. **Required for Apple Pay when the checkout is rendered in a cross-origin iframe.** For example, if your main page is `example.com` and the iframe checkout is hosted at `iframecheckout.com`, you must set this to `example.com` to ensure Apple Pay functions properly. **Additional Requirements:** * The iframe element must include `allow="payment"` attribute * Only supported on Safari 17 or later **apiVersion** `"legacy" | "2.4"` Specifies the API version to use when interacting with the Primer backend. * If not explicitly set, defaults to version `'2.4'`. * Set this to `'legacy'` if you encounter compatibility issues with the latest API version and wish to revert to the previous stable behavior. **Payment lifecycle callbacks** **onPaymentCreationStart** `() =\> void` Notifies you before the checkout tokenizes a payment method and creates a payment. **onBeforePaymentCreate** `(data: object, handler: object) =\> void` Called when a payment will be created. Use as an opportunity to update UI accordingly - for example, to display a "loading" component. The `handler` must be used to then abort or continue with payment creation. Primer will continue with payment creation if `onBeforePaymentCreate` is not implemented. **Parameters** **data** `object` **Properties** **paymentMethodType** `string` The type of the payment method Primer will use for payment creation, one of [PaymentMethodType](https://primer.io/docs/sdk/web/v2.x.x/constants/payment-method-types.md) **handler** `object` Provides two methods to continue or abort the payment. > [!WARNING] > > You MUST call one of the methods of the handler if `onBeforePaymentCreate` is implemented. Choose to abort a payment. ```ts TS theme={"dark"} return handler.abortPaymentCreation(); ``` Choose to continue with payment creation ```ts TS theme={"dark"} return handler.continuePaymentCreation(); ``` You can also pass an idempotency key which will be sent with the payment request to prevent duplicate payments from being created. ```ts TS theme={"dark"} return handler.continuePaymentCreation({ idempotencyKey: 'my-unique-key' }); ``` **onCheckoutComplete** `(data: object) =\> void` Called when a payment has been created. Move on to next step in your checkout flow, such as showing a success message, etc. **Parameters** **data** `object` **Properties** **payment** `object` **Properties** **id** `string` Primer's unique identifier for the payment. **orderId** `string` Your order identifier as provided in the client session. **paymentMethodData** `object` Optional payment method data - for some payment methods this object will contain additional information on the payment. **onCheckoutFail** `(error: PrimerClientError, data: object, handler: object) =\> void` Called when the checkout flow has failed. This callback can also be used to display an error state within your own UI. **Parameters** **error** `PrimerClientError` **Properties** **code** `ErrorCode` **message** `string` **diagnosticsId** `Nullable\` **data** `object` **isFromDeveloper** `boolean` **fromErrorCode** `(code: ErrorCode, options: ErrorOptions) =\> PrimerClientError` **data** `object` **Properties** **payment** `object` When checkout fails, the payment might or might not have been created. If it was created, the payment object contains some information regarding it. **Properties** **id** `string` Primer's unique identifier for the payment. **orderId** `string` Your order identifier as provided in the client session. **paymentMethodData** `object` Optional payment method data - for some payment methods this object will contain additional information on the payment. **handler** `object` Show an error message. If `handler` is `undefined`, the SDK does not expect anything from you. If `handler` exists, you MUST call one of the functions of the handler. ```ts TS theme={"dark"} import { Primer } from "@primer-io/checkout-web"; const checkout = await Primer.showUniversalCheckout(clientToken, { container: "#container", onCheckoutComplete(...args) { console.log("onCheckoutComplete", ...args); }, onCheckoutFail(error, data, handler) { if (!handler) { return; } // Show a default error message return handler.showErrorMessage(); // Or show a custom error message // return handler.showErrorMessage('This is my custom message'); }, }); ``` **Properties** **showErrorMessage** `(customErrorMessage?: string) =\> void` **Parameters** **customErrorMessage?: string** `string` An optional custom error message. **Client session lifecycle callbacks** **onBeforeClientSessionUpdate** `() =\> void` Called when the client session is in the process of being updated. Use it to show a loading indicator on your UI. **onClientSessionUpdate** `(clientSession: ClientSession) =\> void` Called when the client session has been updated by the checkout. Returns the updated client session which can be used to inform your UI. For example updating tax, shipping or discount amounts displayed to your customers. **Event callbacks** **onPaymentMethodAction** `(action: string, data: object) =\> void` Notifies you when a specific payment method has been selected or unselected. **Parameters** **action** `'PAYMENT_METHOD_SELECTED' | 'PAYMENT_METHOD_UNSELECTED'` The action being performed on the payment method. Payment will be unselected when a popup is closed. **data** `object` **Properties** **paymentMethodType** `string` The type of the payment method Primer will use for payment creation, one of [PaymentMethodType](https://primer.io/docs/sdk/web/v2.x.x/constants/payment-method-types.md) **payment** `object | undefined` The payment object, available when a payment has already been created before the payment method is unselected. **Properties** **id** `string` The unique identifier of the payment. **Payment methods options** **card** `object` Customize the appearance and behavior of the card fields in the checkout form. **Properties** **cardholderName** `object` Options for the cardholder name input field. **Properties** **required** `boolean` Whether the cardholder name is required. Only works if the cardholder name is visible. **visible** `boolean` Whether the cardholder name input field should be visible. **placeholder** `string | (options: \{ locale: string \}) =\> string` The placeholder text to display in the cardholder name input field. It can be either a string or a function that returns a string. The function receives an options object as first argument. **cardNumber** `object` Customize the placeholder of the card number field. **Properties** **placeholder** `string | (options: \{ locale: string \}) =\> string` The placeholder text to display in the cardholder number input field. It can be either a string or a function that returns a string. The function receives an options object as first argument. **expiryDate** `object` Customize the placeholder of the expiry date field. **Properties** **placeholder** `string | (options: \{ locale: string \}) =\> string` The placeholder text to display in the expiry date input field. It can be either a string or a function that returns a string. The function receives an options object as first argument. **cvv** `object` Customize the placeholder of the CVV field. **Properties** **placeholder** `string | (options: \{ locale: string \}) =\> string` The placeholder text to display in the CVV input field. It can be either a string or a function that returns a string. The function receives an options object as first argument. **preferredFlow** `"DEDICATED_SCENE" | "EMBEDDED_IN_HOME"` Specify the preferred flow for entering card details. **redirect** `object` Options for payment methods that rely on redirecting. **Properties** **returnUrl** `string` The URL to return to after the redirect process has completed. **forceRedirect** `boolean` Whether to always use a redirect flow, rather than a popup window, even if other options are available. Default value is `false`. **paypal** `object` Options for using PayPal as a payment method. **Properties** **buttonColor** `"gold" | "blue" | "silver" | "white" | "black"` The color of the PayPal button. **buttonShape** `"pill" | "rect"` The shape of the PayPal button. **buttonSize** `"small" | "medium" | "large" | "responsive"` The size of the PayPal button. **buttonHeight** `number` The height of the PayPal button, in pixels. **buttonLabel** `"checkout" | "credit" | "pay" | "buynow" | "paypal" | "installment"` The label displayed on the PayPal button. **buttonTagline** `boolean` Whether to display the PayPal tagline beneath the button. **paymentFlow** `"DEFAULT" | "PREFER_VAULT"` The payment flow to use for the PayPal button. **onClick** `() =\> void` A function to be called when the PayPal button is clicked. **googlePay** `object` Options for using Google Pay as a payment method. **Properties** **buttonType** `"long" | "short" | "book" | "buy" | "checkout" | "donate" | "order" | "pay" | "plain" | "subscribe"` **buttonColor** `"default" | "black" | "white"` The color of the Google Pay button. **buttonSizeMode** `"fill" | "static"` The size mode of the Google Pay button. **onClick** `() =\> void` A function to be called when the Google Pay button is clicked. **captureBillingAddress** `boolean` Whether to prompt the user to select a billing address. **existingPaymentMethodRequired** `boolean` If set to `true`, this specifies that Google Pay can only be used for payments if the user's Google Pay wallet already contains allowed payment methods. When enabled, the SDK will check if [`IsReadyToPayResponse.paymentMethodPresent`](https://developers.google.com/pay/api/web/reference/response-objects#IsReadyToPayResponse) is also `true` before rendering the Google Pay button. Default value is `false`. **applePay** `object` Options for using Apple Pay as a payment method. **Properties** **buttonType** `"plain" | "buy" | "set-up" | "donate" | "check-out" | "book" | "subscribe"` The type of the Apple Pay button to display. **buttonStyle** `"white" | "white-outline" | "black"` The style of the Apple Pay button. **captureBillingAddress** `boolean` *deprecated* Whether to display a prompt for the user to enter their billing address during the payment process. **billingOptions** `object` Billing contact configuration options for Apple Pay. **Properties** **requiredBillingContactFields** `("postalAddress" | "phoneNumber" | "emailAddress")[]` *required* An array of string values that specify which required contact information fields should be collected during the checkout process. **shippingOptions** `object` Shipping contact configuration options for Apple Pay. **Properties** **requiredShippingContactFields** `("postalAddress" | "name" | "phoneNumber" | "emailAddress")[]` *required* An array of string values that specify which required contact information fields should be collected during the checkout process. **adyenKlarna** `object` Options for using Klarna via Adyen as a payment method. **Properties** **buttonOptions** `object` Options for Klarna button. **Properties** **text** `string` Text to be displayed next to the Klarna logo. If provided, it will replace the default `Pay with` text. **klarna** `object` Options for using Klarna as a payment method. **Properties** **paymentFlow** `"DEFAULT" | "PREFER_VAULT"` The payment flow of the Klarna payment method. **recurringPaymentDescription** `string` The description of the recurring payment. **allowedPaymentCategories** `("pay_now" | "pay_later" | "pay_over_time")[]` An array of string values that specify the allowed payment categories. **buttonOptions** `object` Options for Klarna button. **Properties** **text** `string` Text to be displayed next to the Klarna logo. If provided, it will replace the default `Pay with` text. **directDebit** `object` Options for using direct debit as a payment method. **Properties** **customerCountryCode** `string` *required* The customer's two-letter country code. **companyName** `string` *required* The name of the company or organization accepting payments. **companyAddress** `string` *required* The address of the company or organization accepting payments. **customerName** `string` The name of the customer making the payment. **customerEmail** `string` The email address of the customer making the payment. **customerAddressLine1** `string` The first line of the customer's address. **customerAddressLine2** `string` The second line of the customer's address. **customerCity** `string` The city of the customer's address. **customerPostalCode** `string` The postal code of the customer's address. **iban** `string` The International Bank Account Number (IBAN) of the customer's bank account. **submitButtonLabels** `object` An object containing the text to display on the submit button for the Direct Debit form and mandate. **Properties** **form** `string | (options: \{ locale: string \}) =\> string` The label to display on the submit button for the Direct Debit form. **mandate** `string | (options: \{ locale: string \}) =\> string` *required* The label to display on the submit button for the Direct Debit mandate. **giftCard** `object` Options for using gift cards as a payment method. **Properties** **logoSrc** `string` *required* The source URL of the button logo. **background** `string` *required* The background color of the button. **logoAlt** `string` An alternative text for the button logo. **text** `string` The text to display on the button. **Vault options** **vault** `object` An interface for configuring the display of vaulted payment methods. **Properties** **visible** `boolean` Whether the vaulted payment methods are visible or not. If this is not necessary for your use case, we recommend setting this to `false` to skip the retrieval of the vault and speed up the loading of the checkout. Default value is `true`. **deletionDisabled** `boolean` Whether deleting a vaulted payment method is disabled or enabled. **Customization options** **style** `CheckoutStyle` See the [CheckoutStyle](https://primer.io/docs/sdk/web/v2.x.x/checkout-style/Overview.md) page. **form** `object` **Properties** **inputLabelsVisible** `boolean` Choose whether to show the label above inputs. **submitButton** `object` Drop-In Checkout allows you to use your own submit button for submitting forms. By default, the built-in submit button will be favored. Note that when disabling the built-in submit button and using your own custom submit button, it is required to implement the [submit](https://primer.io/docs/sdk/web/v2.x.x/primer-checkout/methods/submit.md) function in order to notify Drop-In Checkout of form submissions. When using your own custom submit button, it's important to use the following callbacks to ensure that your submit button is in the correct state and in sync with the checkout as your customers interact with it. ```ts TS theme={"dark"} const options = { /* Other options ... */ submitButton: { useBuiltInButton: false, // Default to true // Callback for receiving the submit button's visible state in the current scene onVisible(isVisible, context: { currentSceneId }) { // Show or hide your custom submit button }, // Callback for receiving the submit button's disabled state in the current scene onDisable(isDisabled, context: { currentSceneId }) { // Disable or enable your custom submit button }, // Callback for receiving the submit button's loading state in the current scene onLoading(isLoading, context: { currentSceneId }) { // Show your submit button in a loading state }, // Callback for receiving the submit button's content in the current scene onContentChange(content, context: { currentSceneId }) { // Set your submit button's content with either the content provided or your own custom content }, }, }; ``` **Properties** **useBuiltInButton** `boolean` Set whether to use built-in submit button or to display your own custom button. **amountVisible** `boolean` Set whether the total order amount should be displayed in the submit button content. **Callbacks** **onVisible** `(isVisible: boolean, context: object) =\> void` Show or hide your custom submit button. **context** **currentSceneId** `string` An identifier for the current scene. **onDisable** `(isDisabled: boolean, context: object) =\> void` Disable or enable your custom submit button. **context** **currentSceneId** `string` An identifier for the current scene. **onLoading** `(isLoading: boolean, context: object) =\> void` Put your submit button in a loading state. **context** **currentSceneId** `string` An identifier for the current scene. **onContentChange** `(content: string, context: object) =\> void` Set your submit button's content with either the content provided or your own custom content. **context** **currentSceneId** `string` An identifier for the current scene. **processingIndicator** `object` **Properties** **visible** `boolean` Choose whether a processing indicator overlay should be shown on form submission. **errorMessage** `object` **Properties** **disabled** `boolean` Choose whether to allow Universal Checkout to show error messages. **Callbacks** **onErrorMessageShow** `(message: string) =\> void` A callback for when the error message should be displayed, you can choose to use the provided message for your own purposes. **onErrorMessageHide** `() =\> void` A callback for when the error message should be hidden, update own UI accordingly. **successScreen** `false | object` When the checkout is successfully completed, Drop-In Checkout displays a success scene with a default success message "Your payment was successful!". Set the option `successScreen` to modify the default behavior of the success scene. Remove the success screen: ```ts TS theme={"dark"} const options = { /* Other options ... */ successScreen: false, }; ``` Change the message of the default success screen: ```ts TS theme={"dark"} const options = { /* Other options ... */ successScreen: { type: "CHECK", title: "This is a custom success message!", }, }; ``` **Properties** **type** `'CHECK'` "CHECK" is the only type of success screen supported at the moment. **title** `string` Your custom success message. **Manual payment handling** **paymentHandling** `"AUTO" | "MANUAL"` The `paymentHandling` option defines how the SDK should handle payment creation and resume. The default is `AUTO`, set `paymentHandling` to `MANUAL` to turn off automatic payment handling. This disables the callbacks `onBeforePayment` and `onCheckoutComplete`. Two callbacks must be implemented: * `onTokenizeSuccess()` to create payments with the `paymentMethodToken`. * `onResumeSuccess()` to resume payments with `resumeToken`. See the [Manual Payment Creation](https://primer.io/docs/checkout/advanced/manual-payment-creation.md) guide for examples. > [!NOTE] > > The guide's examples are written for `PrimerCheckout`, but the same concepts apply to `PrimerHeadlessCheckout`. **onTokenizeSuccess** `(data: PaymentMethodTokenData, handler: OnTokenizeSuccessHandler) =\> void` > [!NOTE] > > If you set `paymentHandling` to `MANUAL`, implementing this is mandatory. **Parameters** **data** `PaymentMethodTokenData` **Properties** **token** `string` *required* The payment instrument token you can use to [create a payment request](https://primer.io/docs/api-reference/v2.4/api-reference/payments-api/create-a-payment.md) from your backend. **analyticsId** `string` An unique identifier for the payment instrument token. **paymentInstrumentData** `PaymentInstrumentData` Additional information about the payment instrument. Depending on the payment method type, only some of the following properties are present on the object. **Properties** **paymentMethodConfigId** `string` The identifier for the payment method configuration. **paymentMethodType** `string` The type of the payment method used for the transaction, one of [PaymentMethodType](https://primer.io/docs/sdk/web/v2.x.x/constants/payment-method-types.md). **sessionInfo** `SessionInfo` Information about the session associated with the transaction. **first6Digits** `string` The first six digits of the payment card. **firstDigits** `string` The first six or eight digits of the payment card within PCI guidelines. **last4Digits** `string` The last four digits of the payment card. **expirationMonth** `string` The expiration month of the payment card. **expirationYear** `string` The expiration year of the payment card. **cardholderName** `string` The name of the cardholder as it appears on the payment card. **network** `string` The network associated with the payment card (e.g., Visa, Mastercard). **isNetworkTokenized** `string` Indicates whether the payment card's network is tokenized. **binData** `BinData` Information about the Bank Identification Number (BIN) of the payment card. **threeDSecureAuthentication** `ThreeDSAuthenticationData` Data related to 3D Secure authentication for the transaction. **Properties** **responseCode** `ThreeDSecureStatus` Indicates the outcome of the 3D Secure authentication process.\ Possible values: * `AUTH_SUCCESS`: The authentication was successful. * `AUTH_FAILED`: The authentication process failed. * `SKIPPED`: The authentication was skipped. * `CHALLENGE`: A challenge was issued during the authentication process. **reasonCode** `string` An optional code indicating the reason for the outcome of the 3D Secure authentication. **reasonText** `string` An optional text description providing further details about the reason for the authentication outcome. **protocolVersion** `string` Specifies the version of the 3D Secure protocol that was used. **challengeIssued** `boolean` Indicates whether a challenge was issued as part of the authentication process. * `true`: A challenge was issued. * `false`: No challenge was issued. **paypalBillingAgreementId** `string` The identifier for a PayPal billing agreement, if applicable. **externalPayerInfo** `ExternalPayerInfo` External information about the payer associated with the transaction. **shippingAddress** `ShippingAddress` The shipping address for the transaction, if applicable. **klarnaCustomerToken** `string` The customer token associated with Klarna payment, if applicable. **sessionData** `SessionData` Additional data related to the session. **paymentInstrumentType** `PaymentInstrumentType` The type of the payment instrument. Example of possible values (new values could be added as we add new payment methods): * `APPLE_PAY` * `CARD_OFF_SESSION_PAYMENT` * `GOOGLE_PAY` * `KLARNA_CUSTOMER_TOKEN` * `OFF_SESSION_PAYMENT` * `PAYMENT_CARD` * `PAYPAL_BILLING_AGREEMENT` * `PAYPAL_ORDER` **threeDSecureAuthentication** `ThreeDSAuthenticationData` Data related to 3D Secure authentication for the transaction. **Properties** **responseCode** `ThreeDSecureStatus` Indicates the outcome of the 3D Secure authentication process.\ Possible values: * `AUTH_SUCCESS`: The authentication was successful. * `AUTH_FAILED`: The authentication process failed. * `SKIPPED`: The authentication was skipped. * `CHALLENGE`: A challenge was issued during the authentication process. **reasonCode** `string` An optional code indicating the reason for the outcome of the 3D Secure authentication. **reasonText** `string` An optional text description providing further details about the reason for the authentication outcome. **protocolVersion** `string` Specifies the version of the 3D Secure protocol that was used. **challengeIssued** `boolean` Indicates whether a challenge was issued as part of the authentication process. * `true`: A challenge was issued. * `false`: No challenge was issued. **tokenType** `"SINGLE_USE" | "MULTI_USE"` Whether this payment method token can be used only once or multiple times. **vaultData** `VaultData` **Properties** **customerId** `string` The `customerId` associated to the payment method, if vaulted. **handler** `OnTokenizeSuccessHandler` **Properties** **handleSuccess** `() =\> void` Display a success screen. **handleFailure** `(errorMessage: string) =\> void` Display `errorMessage` as an error or failure message. **continueWithNewClientToken** `(clientToken: string) =\> void` Continue the payment flow using the given `clientToken`. Called after a customer submitted their payment data and the payment details have been tokenized. You'll receive a `paymentMethodToken` in `onTokenizeSuccess()`. * [Create a payment request](https://primer.io/docs/api-reference/v2.4/api-reference/payments-api/create-a-payment.md) passing the `paymentMethodToken` to your backend * If the payment is successful, call `handler.handleSuccess()` in order to display a success screen * If the payment is unsuccessful, call `handler.handleFailure(errorMessage)` to display an error or failure message * Payments API may return a new `clientToken` for additional steps (in the `requiredActions` on the response). In this case, call `handler.continueWithNewClientToken(clientToken)` to continue with the payment flow **onTokenizeError** `(error: PrimerClientError) =\> void` Called after a customer submitted their payment data and the payment details could not be tokenized. Use the `PrimerClientError` data to display an error message. **Parameters** **error** `PrimerError` **Properties** **code** `ErrorCode` **message** `string` **diagnosticsId** `Nullable\` **data** `object` **isFromDeveloper** `boolean` **fromErrorCode** `(code: ErrorCode, options: ErrorOptions) =\> PrimerClientError` **onResumeSuccess** `(data: ResumeToken, handler: OnResumeSuccessHandler) =\> void` Called when the resume token must be sent to your server to resume the payment flow, typically after the customer has completed some authorization step outside of the Primer SDK. > [!NOTE] > > If you set `paymentHandling` to `MANUAL`, handling `onResumeSuccess()` is required to fully support 3DS and the majority of payment methods. **Parameters** **data** `ResumeToken` **Properties** **resumeToken** `string` The resume token you can use to [resume the payment flow](https://primer.io/docs/api-reference/v2.4/api-reference/payments-api/resume-a-payment.md) on your backend. **paymentId** `string` An unique identifier of the payment on Primer. **handler** `OnResumeSuccessHandler` **Properties** **handleSuccess** `() =\> void` Display a success screen. **handleFailure** `(errorMessage: string) =\> void` Display `errorMessage` as an error or failure message. **continueWithNewClientToken** `(clientToken: string) =\> void` Continue the payment flow using the given `clientToken`. * You will receive a `resumeToken` via the `onResumeSuccess()` callback if applicable * Send a [resume payment request](https://primer.io/docs/api-reference/v2.4/api-reference/payments-api/resume-a-payment.md) with the `resumeToken` * If the payment is successful, call `handler.handleSuccess()` in order to display a success screen * If the payment is unsuccessful, call `handler.handleFailure(errorMessage)` to display an error or failure message * The Payments API may again return a new `clientToken` for additional steps. In this case, call `handler.continueWithNewClientToken(clientToken)` again **onResumeError** `(error: PrimerClientError) =\> void` Called when the payment cannot be resumed. Use the `PrimerClientError` data to display an error message. **Parameters** **error** `PrimerError` **Properties** **code** `ErrorCode` **message** `string` **diagnosticsId** `Nullable\` **data** `object` **isFromDeveloper** `boolean` **fromErrorCode** `(code: ErrorCode, options: ErrorOptions) =\> PrimerClientError` **onTokenizeShouldStart** `(data: \{ paymentMethodType: PaymentMethodType \}) =\> boolean` Called to determine if the payment method tokenization should start. **Parameters** **data** `\{ paymentMethodType: PaymentMethodType \}` An object containing a `paymentMethodType` property, one of [PaymentMethodType](https://primer.io/docs/sdk/web/v2.x.x/constants/payment-method-types.md). Implement this if you need to abort the payment method tokenization according to your own logic. You should return `true` to continue or `false` to abort. **onTokenizeStart** `() =\> void` Called just before the payment method tokenization starts. Implement this to perform any custom action, for example, displaying a custom loading indicator. **onTokenizeDidNotStart** `(reason: "TOKENIZATION_DISABLED" | "TOKENIZATION_SHOULD_NOT_START") =\> void` Called if the payment method tokenization did not start. Receives a `reason` as a string. **Parameters** **reason** `"TOKENIZATION_SHOULD_NOT_START" | "TOKENIZATION_DISABLED"` * `TOKENIZATION_SHOULD_NOT_START`: tokenization was interrupted returning `false` from `onTokenizeShouldStart`. * `TOKENIZATION_DISABLED`: tokenization was disabled using `setIsTokenizationEnabled` or `setPaymentCreationEnabled`. **Client session caching** **clientSessionCachingEnabled** `boolean` > [!WARNING] > > Before enabling the flag to `true` it's recommended to reach out to Primer support for additional verification since there are edge cases where it's not advised. Indicates whether client session caching is enabled. When set to `true`, responses from the server will be cached on the client side, allowing for faster subsequent access to the same data within the cache duration. When set to `false`, every request to the server will be processed without utilizing any client-side cache, ensuring that the client always receives the most up-to-date data. ## Returns A promise that is resolved when Drop-In Checkout has been properly rendered on the page, or rejected if any error occurred during initialisation. The promise is resolved with an instance of [PrimerCheckout](https://primer.io/docs/sdk/web/v2.x.x/primer-checkout/overview.md) This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.