Start Klarna Checkout

POST

api

domains

{domain}

express

klarna

start

Start Klarna Checkout

curl --request POST \
  --url https://cc.firmly.work/api/v1/domains/{domain}/express/klarna/start \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --header 'x-firmly-authorization: <x-firmly-authorization>' \
  --data '
{
  "attributes": {}
}
'

import requests

url = "https://cc.firmly.work/api/v1/domains/{domain}/express/klarna/start"

payload = { "attributes": {} }
headers = {
    "x-firmly-authorization": "<x-firmly-authorization>",
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

response = requests.post(url, json=payload, headers=headers)

print(response.text)

const options = {
  method: 'POST',
  headers: {
    'x-firmly-authorization': '<x-firmly-authorization>',
    Authorization: 'Bearer <token>',
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({attributes: {}})
};

fetch('https://cc.firmly.work/api/v1/domains/{domain}/express/klarna/start', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://cc.firmly.work/api/v1/domains/{domain}/express/klarna/start",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => json_encode([
    'attributes' => [
        
    ]
  ]),
  CURLOPT_HTTPHEADER => [
    "Authorization: Bearer <token>",
    "Content-Type: application/json",
    "x-firmly-authorization: <x-firmly-authorization>"
  ],
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://cc.firmly.work/api/v1/domains/{domain}/express/klarna/start"

	payload := strings.NewReader("{\n  \"attributes\": {}\n}")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("x-firmly-authorization", "<x-firmly-authorization>")
	req.Header.Add("Authorization", "Bearer <token>")
	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

HttpResponse<String> response = Unirest.post("https://cc.firmly.work/api/v1/domains/{domain}/express/klarna/start")
  .header("x-firmly-authorization", "<x-firmly-authorization>")
  .header("Authorization", "Bearer <token>")
  .header("Content-Type", "application/json")
  .body("{\n  \"attributes\": {}\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://cc.firmly.work/api/v1/domains/{domain}/express/klarna/start")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["x-firmly-authorization"] = '<x-firmly-authorization>'
request["Authorization"] = 'Bearer <token>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"attributes\": {}\n}"

response = http.request(request)
puts response.read_body

{
  "cart_id": "<string>",
  "line_items": [
    {}
  ],
  "payment_method": {
    "payment_type": "<string>",
    "attributes": {
      "session_id": "<string>",
      "client_token": "<string>",
      "payment_method_categories": [
        {}
      ]
    }
  },
  "shipping_info": {},
  "shipping_method": {},
  "total": {},
  "sub_total": {},
  "tax": {}
}

Overview

Initiates a Klarna checkout by creating a payment session with Klarna. Returns the cart enriched with a payment_method object containing the client_token, session_id, and available payment_method_categories needed to render the Klarna Payments widget on the client.

Authentication

string

required

Device authentication token from Browser Session

Path Parameters

string

required

The merchant domain (e.g., “merchant.example.com”)

Request Body

object

Optional gateway-specific attributes. Can be an empty object or omitted entirely for standard Klarna checkout.

Response

Returns the cart enriched with the Klarna payment method details.

string

Unique identifier for the cart

array

Array of items in the cart

object

Klarna payment method details

Show Payment Method

string

Always "Klarna" for this gateway

object

Klarna session credentials

Show Attributes

string

Klarna payment session identifier

string

Token used to initialize the Klarna Payments SDK on the client

array

Available Klarna payment options (e.g., pay_later, pay_over_time, pay_now). Each entry contains identifier, name, and asset_urls.

object

Delivery address details

object

Selected shipping method with pricing

object

Grand total including all costs

object

Subtotal before shipping and tax

object

Tax amount

Code Example

const response = await fetch(
  'https://cc.firmly.work/api/v1/domains/merchant.example.com/express/klarna/start',
  {
    method: 'POST',
    headers: {
      'x-firmly-authorization': authToken,
      'Content-Type': 'application/json'
    },
    body: JSON.stringify({})
  }
);

const cart = await response.json();

// Extract Klarna credentials for the widget
const {
  session_id,
  client_token,
  payment_method_categories
} = cart.payment_method.attributes;

// Initialize Klarna Payments SDK with client_token
Klarna.Payments.init({ client_token });

import requests

response = requests.post(
    'https://cc.firmly.work/api/v1/domains/merchant.example.com/express/klarna/start',
    headers={
        'x-firmly-authorization': auth_token,
        'Content-Type': 'application/json'
    },
    json={}
)

cart = response.json()
klarna_attrs = cart['payment_method']['attributes']
session_id = klarna_attrs['session_id']
client_token = klarna_attrs['client_token']
categories = klarna_attrs['payment_method_categories']

curl -X POST https://cc.firmly.work/api/v1/domains/merchant.example.com/express/klarna/start \
  -H "x-firmly-authorization: YOUR_AUTH_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{}'

Response Example

{
  "cart_id": "9cf76530-1344-420f-9ca6-c7a96fb6db45",
  "line_items": [
    {
      "line_item_id": "3e66bef5-43f5-4a80-8957-91c5c8233163",
      "sku": "MT12",
      "quantity": 1,
      "description": "Cassius Sparring Tank",
      "price": {
        "currency": "USD",
        "value": 18,
        "number": 1800,
        "symbol": "$"
      },
      "line_price": {
        "currency": "USD",
        "value": 18,
        "number": 1800,
        "symbol": "$"
      }
    }
  ],
  "payment_method": {
    "payment_type": "Klarna",
    "attributes": {
      "session_id": "kp_abc123def456",
      "client_token": "eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9...",
      "payment_method_categories": [
        {
          "identifier": "pay_later",
          "name": "Pay later",
          "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"
          }
        },
        {
          "identifier": "pay_over_time",
          "name": "Financing",
          "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"
          }
        }
      ]
    }
  },
  "shipping_info": {
    "first_name": "John",
    "last_name": "Smith",
    "email": "john@example.com",
    "phone": "2065551212",
    "address1": "123 Main St",
    "city": "Seattle",
    "state_or_province": "WA",
    "country": "US",
    "postal_code": "98101"
  },
  "shipping_method": {
    "id": "standard_shipping",
    "description": "Standard Shipping",
    "price": {
      "currency": "USD",
      "value": 10,
      "number": 1000,
      "symbol": "$"
    }
  },
  "total": {
    "currency": "USD",
    "value": 30,
    "number": 3000,
    "symbol": "$"
  },
  "sub_total": {
    "currency": "USD",
    "value": 18,
    "number": 1800,
    "symbol": "$"
  },
  "tax": {
    "currency": "USD",
    "value": 2,
    "number": 200,
    "symbol": "$"
  }
}

Error Responses

Code	Description
`ErrorCartNotFound`	No active cart for this domain
`ErrorGatewayNotFound`	Klarna is not enabled for this merchant
`ErrorOperationNotSupported`	Merchant adapter does not support Klarna
`ErrorStartExpressCheckout`	Failed to create Klarna payment session
`ErrorStoreUnavailable`	Merchant temporarily unavailable

Authorize Klarna Checkout - Confirm Klarna authorization
Complete Klarna Order - Finalize the order

⌘I

Start Klarna Checkout

curl --request POST \
  --url https://cc.firmly.work/api/v1/domains/{domain}/express/klarna/start \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --header 'x-firmly-authorization: <x-firmly-authorization>' \
  --data '
{
  "attributes": {}
}
'

import requests

url = "https://cc.firmly.work/api/v1/domains/{domain}/express/klarna/start"

payload = { "attributes": {} }
headers = {
    "x-firmly-authorization": "<x-firmly-authorization>",
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

response = requests.post(url, json=payload, headers=headers)

print(response.text)

const options = {
  method: 'POST',
  headers: {
    'x-firmly-authorization': '<x-firmly-authorization>',
    Authorization: 'Bearer <token>',
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({attributes: {}})
};

fetch('https://cc.firmly.work/api/v1/domains/{domain}/express/klarna/start', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://cc.firmly.work/api/v1/domains/{domain}/express/klarna/start",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => json_encode([
    'attributes' => [
        
    ]
  ]),
  CURLOPT_HTTPHEADER => [
    "Authorization: Bearer <token>",
    "Content-Type: application/json",
    "x-firmly-authorization: <x-firmly-authorization>"
  ],
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://cc.firmly.work/api/v1/domains/{domain}/express/klarna/start"

	payload := strings.NewReader("{\n  \"attributes\": {}\n}")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("x-firmly-authorization", "<x-firmly-authorization>")
	req.Header.Add("Authorization", "Bearer <token>")
	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

HttpResponse<String> response = Unirest.post("https://cc.firmly.work/api/v1/domains/{domain}/express/klarna/start")
  .header("x-firmly-authorization", "<x-firmly-authorization>")
  .header("Authorization", "Bearer <token>")
  .header("Content-Type", "application/json")
  .body("{\n  \"attributes\": {}\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://cc.firmly.work/api/v1/domains/{domain}/express/klarna/start")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["x-firmly-authorization"] = '<x-firmly-authorization>'
request["Authorization"] = 'Bearer <token>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"attributes\": {}\n}"

response = http.request(request)
puts response.read_body

{
  "cart_id": "<string>",
  "line_items": [
    {}
  ],
  "payment_method": {
    "payment_type": "<string>",
    "attributes": {
      "session_id": "<string>",
      "client_token": "<string>",
      "payment_method_categories": [
        {}
      ]
    }
  },
  "shipping_info": {},
  "shipping_method": {},
  "total": {},
  "sub_total": {},
  "tax": {}
}

Home

Core Concepts

Implementation Guides

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API Reference

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Resources

Start Klarna Checkout

Overview

Authentication

Path Parameters

Request Body

Response

Code Example

Response Example

Error Responses

​Overview

​Authentication

​Path Parameters

​Request Body

​Response

​Code Example

​Response Example

​Error Responses

​Related Endpoints

Overview

Authentication

Path Parameters

Request Body

Response

Code Example

Response Example

Error Responses

Related Endpoints