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POST
/
api
/
v1
/
domains
/
{domain}
/
express
/
klarna
/
authorize
Authorize Klarna Checkout
curl --request POST \
  --url https://cc.firmly.work/api/v1/domains/{domain}/express/klarna/authorize \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --header 'x-firmly-authorization: <x-firmly-authorization>' \
  --data '
{
  "attributes": {
    "authorization_token": "<string>"
  }
}
'
{
  "cart_id": "<string>",
  "line_items": [
    {}
  ],
  "payment_method": {
    "payment_type": "<string>",
    "attributes": {
      "session_id": "<string>",
      "authorization_token": "<string>"
    }
  },
  "shipping_info": {},
  "total": {},
  "sub_total": {},
  "tax": {}
}

Documentation Index

Fetch the complete documentation index at: https://developers.firmly.ai/llms.txt

Use this file to discover all available pages before exploring further.

​
Overview

After the customer authorizes payment in the Klarna widget (client-side), this endpoint confirms the authorization with Firmly. It stores the authorization_token in the session and returns the cart with the confirmed Klarna payment method.

​
Authentication

​
x-firmly-authorization
string
required
Device authentication token from Browser Session

​
Path Parameters

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

​
Request Body

​
attributes
object
required
Klarna authorization details

​
Response

Returns the cart with the confirmed Klarna payment method.
​
cart_id
string
Unique identifier for the cart
​
line_items
array
Array of items in the cart
​
payment_method
object
Confirmed Klarna payment method
​
shipping_info
object
Delivery address details
​
total
object
Grand total including all costs
​
sub_total
object
Subtotal before shipping and tax
​
tax
object
Tax amount

​
Code Example

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

const cart = await response.json();
// Payment is now authorized, proceed to complete order

​
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",
      "authorization_token": "klarna_auth_token_from_widget"
    }
  },
  "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"
  },
  "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

CodeDescription
ErrorCartNotFoundNo active cart for this domain
ErrorBadRequestMissing authorization_token in request body
ErrorGatewayNotFoundKlarna is not enabled for this merchant
ErrorPreconditionPrecondition failed (e.g., cart state invalid)
ErrorSubmitExpressCheckoutAuthorization failed at the merchant