klarna

Create a Klarna payment session

Creates a Klarna payment session for the cart and returns the session_id and client_token used to render the Klarna widget client-side. The session intent is derived server-side from the cart’s contents (buy, or buy_and_tokenize when the cart contains a subscription); the optional intent field is accepted for compatibility but ignored. Cart-token authenticated. Returns 400 when Klarna rejects the session, 404 when the cart is not found, 410 when the cart has already been processed or holds an authorized enrollment, and 422 when the request body fails validation.

POST

api

payments

v2026-04

carts

{cart_token}

klarna

sessions

Create a Klarna payment session

curl --request POST \
  --url https://api.fluid.app/api/payments/v2026-04/carts/{cart_token}/klarna/sessions \
  --header 'Content-Type: application/json' \
  --data '{}'

import requests

url = "https://api.fluid.app/api/payments/v2026-04/carts/{cart_token}/klarna/sessions"

payload = {}
headers = {"Content-Type": "application/json"}

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

print(response.text)

const options = {
  method: 'POST',
  headers: {'Content-Type': 'application/json'},
  body: JSON.stringify({})
};

fetch('https://api.fluid.app/api/payments/v2026-04/carts/{cart_token}/klarna/sessions', 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://api.fluid.app/api/payments/v2026-04/carts/{cart_token}/klarna/sessions",
  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([
    
  ]),
  CURLOPT_HTTPHEADER => [
    "Content-Type: application/json"
  ],
]);

$response = curl_exec($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://api.fluid.app/api/payments/v2026-04/carts/{cart_token}/klarna/sessions"

	payload := strings.NewReader("{}")

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

	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://api.fluid.app/api/payments/v2026-04/carts/{cart_token}/klarna/sessions")
  .header("Content-Type", "application/json")
  .body("{}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://api.fluid.app/api/payments/v2026-04/carts/{cart_token}/klarna/sessions")

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

request = Net::HTTP::Post.new(url)
request["Content-Type"] = 'application/json'
request.body = "{}"

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

{
  "success": true,
  "session_id": "klarna_sess_9f8e7d6c",
  "client_token": "klarna_ct_abc123",
  "meta": {
    "request_id": "018f2c1a-8b3a-7e6d-9f10-2a3b4c5d6e7f",
    "timestamp": "2026-04-01T12:00:00Z"
  }
}

{
  "error_message": "<string>",
  "errors": "<string>",
  "meta": {
    "request_id": "<string>",
    "timestamp": "2023-11-07T05:31:56Z"
  }
}

{
  "error_message": "<string>",
  "errors": "<string>",
  "meta": {
    "request_id": "<string>",
    "timestamp": "2023-11-07T05:31:56Z"
  }
}

{
  "error_message": "<string>",
  "errors": "<string>",
  "meta": {
    "request_id": "<string>",
    "timestamp": "2023-11-07T05:31:56Z",
    "shop_url": "<string>",
    "cart": {}
  }
}

{
  "error_message": "<string>",
  "errors": "<string>",
  "meta": {
    "request_id": "<string>",
    "timestamp": "2023-11-07T05:31:56Z"
  }
}

Path Parameters

cart_token

string

required

Opaque cart token returned by the create-cart response. It scopes the request to a single cart and is the credential for these endpoints — cart-token authentication carried in the path, with no bearer token or API key.

Body

application/json

intent

string

Accepted for compatibility but ignored — the session intent is derived from the cart's contents.

Response

Session created

Success body for Klarna session creation.

success

boolean

required

true when the Klarna session was created.

session_id

string | null

required

Klarna session id, reused on the update endpoint; null when Klarna returned no session.

client_token

string | null

required

Klarna client token used to render the Klarna payment widget in the browser; null when Klarna returned none.

meta

object

required

Standard response metadata included on every response.

Show child attributes

Create a Klarna payment session

curl --request POST \
  --url https://api.fluid.app/api/payments/v2026-04/carts/{cart_token}/klarna/sessions \
  --header 'Content-Type: application/json' \
  --data '{}'

import requests

url = "https://api.fluid.app/api/payments/v2026-04/carts/{cart_token}/klarna/sessions"

payload = {}
headers = {"Content-Type": "application/json"}

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

print(response.text)

const options = {
  method: 'POST',
  headers: {'Content-Type': 'application/json'},
  body: JSON.stringify({})
};

fetch('https://api.fluid.app/api/payments/v2026-04/carts/{cart_token}/klarna/sessions', 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://api.fluid.app/api/payments/v2026-04/carts/{cart_token}/klarna/sessions",
  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([
    
  ]),
  CURLOPT_HTTPHEADER => [
    "Content-Type: application/json"
  ],
]);

$response = curl_exec($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://api.fluid.app/api/payments/v2026-04/carts/{cart_token}/klarna/sessions"

	payload := strings.NewReader("{}")

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

	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://api.fluid.app/api/payments/v2026-04/carts/{cart_token}/klarna/sessions")
  .header("Content-Type", "application/json")
  .body("{}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://api.fluid.app/api/payments/v2026-04/carts/{cart_token}/klarna/sessions")

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

request = Net::HTTP::Post.new(url)
request["Content-Type"] = 'application/json'
request.body = "{}"

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

{
  "success": true,
  "session_id": "klarna_sess_9f8e7d6c",
  "client_token": "klarna_ct_abc123",
  "meta": {
    "request_id": "018f2c1a-8b3a-7e6d-9f10-2a3b4c5d6e7f",
    "timestamp": "2026-04-01T12:00:00Z"
  }
}

{
  "error_message": "<string>",
  "errors": "<string>",
  "meta": {
    "request_id": "<string>",
    "timestamp": "2023-11-07T05:31:56Z"
  }
}

{
  "error_message": "<string>",
  "errors": "<string>",
  "meta": {
    "request_id": "<string>",
    "timestamp": "2023-11-07T05:31:56Z"
  }
}

{
  "error_message": "<string>",
  "errors": "<string>",
  "meta": {
    "request_id": "<string>",
    "timestamp": "2023-11-07T05:31:56Z",
    "shop_url": "<string>",
    "cart": {}
  }
}

{
  "error_message": "<string>",
  "errors": "<string>",
  "meta": {
    "request_id": "<string>",
    "timestamp": "2023-11-07T05:31:56Z"
  }
}

Overview

Task guides

Portal & Widgets

Endpoints

Auth endpoints

Checkout endpoints

Public SDK endpoints

Member endpoints

Payment gateway endpoints

Cart payment endpoints

Commerce endpoints

Webhooks endpoints

Company admin endpoints (v0)

Analytics

Create a Klarna payment session

Path Parameters

Body

Response