Klarna's API relies on standard HTTP response codes to signal the success or failure of a request. When an API call is successful, Klarna will respond with a 2xx status code and when the API call fails Klarna will respond with a 4xx or 5xx status code together with a response body containing an error object with the error code, an array of error messages and a unique correlation id to be used to identify the request.

• 2xx codes indicate success.
• 4xx codes indicate an an error on the client side (e.g., missing parameters or failed transactions).
• 5xx codes indicate server-side errors.