Important information

The API reference is now available here.
The deprecated API reference is available here.


Error handling

Learn more about errors and how we communicate them.


Unzer API errors are returned in the JSON response and consist of a code, merchantMessage, and customerMessage. We recommend showing the customer message in the frontend of your customer and logging all the fields of unexpected errors for further investigation. You should also store the fields id and traceId that are useful when you need to find the root cause for an error. The id can also be used to fetch a specific error object later for analysis as described in the retrieving errors by ID section.

Error responses do not always have an HTTP error status code. This means that the response would contain a 2XX HTTP status code that still has a list of errors in its payload.
  "id": "p-err-d0d2096c9bb04a2e8cecf776601",
  "isSuccess": false,
  "isPending": false,
  "isError": true,
  "url": "",
  "timestamp": "2021-07-30 11:43:39",
  "traceId": "b7842b4951bc3752406e6e3f3c51a217",
  "errors": [
      "code": "API.410.200.001",
      "merchantMessage": "lastName is missing",
      "customerMessage": "lastName is missing. Please contact us for more information."
      "code": "API.410.200.004",
      "merchantMessage": "firstName is missing.",
      "customerMessage": "firstName is missing. Please contact us for more information."

HTTP response codes for errors

CodeHTTP ResponsePossible causes
400Bad RequestBad request to the API, for example, required parameter is missing or has an invalid syntax.
401UnauthorizedRequest without a key or with an invalid key.
403Access-Denied/ForbiddenRequest to a private resource with a public key.
404Not FoundThe requested resource does not exist.
405Method Not AllowedThe chosen payment type is not configured for the merchant or the HTTP method can not be used for the requested resource.
415Unsupported media typeThe request media type is not supported by the system.
500Internal Server ErrorAn error occurred in a subsequent system:Unzer API, Payment Core, SDM, Partner System, and so on.
504Gateway TimeoutThe server did not receive a fast enough response from another server upstream when it attempted to load one of the web pages.

Unzer Error components

Error responses contain the information about the origin of the error in the form of a JSON object. Within the error object, there is a list of errors specifying all the possible problems in a chunk.

  "code": "API.410.200.004",
  "merchantMessage": "firstName is missing.",
  "customerMessage": "firstName is missing. Please contact us for more information."
codeUniquely identifies the error, for example API.410.200.004.
merchantMessageSpecifies the error details and further information for you as a merchant. The message is not intended to be displayed to the customer and always appears in English. This message is only visible if you make the call with a private key. If you are using a public key, this field is missing.
customerMessageSpecifies the message to be displayed to your customer. It is available in several languages, based on the Accept Language header.

To learn more about how to set the language for the error messages, see Localization and languages.

Retrieving errors by ID

You can retrieve each error object you received in the past, by using its unique ID. To learn more, see Fetch error object

Handling server-side errors

Log the errors, the error object ID etc. and show the `customerMessage` to the client, if applicable.
try {
    $unzer     = new UnzerSDK\Unzer('s-priv-xxxxxxxxxx');

    $chargeInstance = new Charge(100.00, 'EUR', $returnUrl);
    $transaction = $unzer->performCharge($chargeInstance, $typeId);
} catch (UnzerApiException $e) {
    // write $e->getMerchantMessage(), $e->getErrorId() and $e->getCode() to your log
    // show $e->getClientMessage() on the client side if applicable
try {
    charge = sepa.charge(new BigDecimal(119.0), Currency.getInstance("EUR"), new URL("https://your.return.url"));
} catch (PaymentException e) {
    // write the error information from the PaymentExceptions field paymentErrorList to your log
    // show the field customerMessage from the paymentErrors on the client side if applicable

See also

Error codes