Authentication

This section of the guide walks you through initiating a payment and letting your customers pay with Klarna.

When your customer wants to pay with Klarna, you have to open a payment session and share the shopping cart details in a POST request to the {apiURL}/payments/v1/sessions endpoint. In that request, you also specify if the payment is one-time or recurring.

Once you start a payment session, it stays open for 48 hours or until you place an order. You can also send a separate POST request to cancel the session.

Klarna payments API uses HTTP basic authentication. To authenticate, use your API credentials that consist of:

A username linked to your Klarna merchant ID (MID)
A password associated with your username

If you're using an API platform that lets you store your credentials, you can add them in relevant fields. Otherwise, make sure to include the Base64-encoded username:password in the Authorization header field of each API request, as shown below.

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Authorization: Basic pwhcueUff0MmwLShJiBE9JHA==

A sample authorization request header with Base64-encoded credentials.

Common parameters

To get a success response, include the following required parameters in your POST {apiURL}/payments/v1/sessions request.

Parameter	Description
`locale`	The language of information presented on the Klarna widget. Learn more about using locale in API calls.
`purchase_country` required	The country where the purchase is made. Learn more about supported countries.
`purchase_currency` required	The currency in which the customer is charged. Learn more about supported currencies.
`order_amount` required	The total price of the order, including tax and discounts.
`order_lines` required	The details of order lines in the purchase.
`intent`	The purpose of the payment session.
`merchant_urls.authorization`	Get a callback once the customer has completed the flow and you can create an order.

We recommend you don't include customer details when initiating a payment session. Instead, use the authorize() call to share them with Klarna at a later stage of the checkout process when the customer clicks Buy.

Payment scenarios and intent

As we already mentioned, you can use Klarna payments in a variety of payment scenarios. Depending on the scenario, add the right value in the intent field of the request.

For one-time payments, set intent to buy.

For recurring payments:

Set intent to tokenize if you don't want to place an order at checkout.
Set intent to buy_and_tokenize if you want to place the first order at checkout.
Set intent to buy_and_default_tokenize if you want to place the first order at checkout and add an additional service at the same time.

The intent you set for a session determines the steps you need to take when creating an order later in the process.

One-time payment

To open a one-time payment session, include all common parameters in the request body and set intent to buy.

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{
"acquiring_channel": "ECOMMERCE",
"intent": "buy",
"purchase_country": "SE",
"purchase_currency": "SEK",
"locale": "en-SE",
"order_amount": 9500,
"order_tax_amount": 1900,
"order_lines": [
{

A sample POST request to create a one-time payment session.

Recurring payment without payment at checkout

To enable recurring payments without charging your customer at checkout, include the following in your request:

All common parameters
intent set to tokenize
The subscription details in the subscription object

You can charge the customer later using a customer token created in the same Klarna payments session.

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{
"acquiring_channel": "ECOMMERCE",
"intent": "tokenize",
"purchase_country": "SE",
"purchase_currency": "SEK",
"locale": "en-SE",
"order_amount": 9999,
"order_tax_amount": 2000,
"order_lines": [
{

A sample POST request to enable recurring payments.

Recurring payment with payment at checkout

To charge the customer at checkout and enable recurring payments at the same time, include the following in your request:

All common parameters
intent set to buy_and_tokenize
The subscription details in the subscription object

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{
"acquiring_channel": "ECOMMERCE",
"intent": "buy_and_tokenize",
"purchase_country": "SE",
"purchase_currency": "SEK",
"locale": "en-SE",
"order_amount": 9999,
"order_tax_amount": 2000,
"order_lines": [
{

A sample POST request to charge the customer at checkout and enable recurring payments.

Recurring payment with mixed payments at the checkout

Mixed payments allows you to charge the customer at the checkout for one item and enable future orders by tokenizing another payment method.

All common parameters
intent set to buy_and_default_tokenize
The subscription details in the subscription object

You will be able to charge the customer later using a customer token.

Success response

In response to a create session call, you receive:

session_id, a payment session identifier you can use to [ update the session] and [ retrieve session] details
client_token, a token you pass to the JavaScript SDK or Mobile SDK(Android, iOS and React Native) to launch the Klarna widget
payment_method_categories, an array that lists the grouped Klarna payment methods available for the session. We can respond with one or more categories depending on the market and account configuration.

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{
"session_id": "068df369-13a7-4d47-a564-62f8408bb760",
"client_token": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpZCI6IjAwMDAwMDAwMDAtMDAwMDAtMDAwMC0wMDAwMDAwMC0wMDAwIiwidXJsIjoiaHR0cHM6Ly9jcmVkaXQtZXUua2xhcm5hLmNvbSJ9.A_rHWMSXQN2NRNGYTREBTkGwYwtm-sulkSDMvlJL87M",
"payment_method_categories": [
{
"identifier": "klarna"
"name" : "Pay with Klarna",
"asset_urls" : {
"descriptive" : "https://x.klarnacdn.net/payment-method/assets/badges/generic/klarna.svg",
"standard" : "https://x.klarnacdn.net/payment-method/assets/badges/generic/klarna.svg"

A sample success response to the create session call.

Error response

If your request doesn't pass our validation, you'll receive an error response.

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{
"correlation_id": "6a9b1cb1-73a3-4936-a030-481ba4bb203b",
"error_code": "BAD_VALUE",
"error_messages": [
"Bad value: order_lines"
]
}

A sample error response caused by incorrect order line details.

Go to Error Handling to learn more about common errors and troubleshooting suggestions. You can use the value in correlation_id to find entries related to the request under Logs in the Merchant portal.