Notification webhooks

Adyen sends notifications through webhooks to inform your system about events that occur in the balance platform. These events include when a card user makes a payment with their Adyen-issued card, or when a merchant starts a refund. When an event occurs, Adyen makes an HTTP POST request to a URL on your server and includes the details of the event in the request body.

You can use notifications to build your implementations. For example, you can use the information to update balances in your own dashboards or to keep track of incoming funds.

On this page, you'll find information about how to:

1. Set up your webhook endpoint.
2. (Optional) Validate HMAC signatures.
3. Accept a notification.

Set up a webhook endpoint

Create an endpoint on your server that:

• Can receive a JSON object.
• Has an open TCP port for HTTPS traffic on port 443, 8443, or 8843.
• Can handle basic authentication.

After you have an endpoint ready, reach out to your Adyen contact so we can configure the endpoint and provide basic authentication credentials. We'll also share an HMAC secret key that you can use to validate HMAC signatures.

Next, when you are already receiving webhooks, make sure that you accept every notification.

Validate the HMAC signature

Adyen signs every notification with an HMAC signature in the request header. You can optionally verify the HMAC signature to add an extra layer of security. By verifying this signature, you'll confirm that the notification was sent by Adyen and was not modified during transmission.

1. For every notification that you receive, get the values from the following headers:
   • HmacSignature: Contains the signature.
   • Protocol: The protocol used to create the signature, HmacSHA256.

2. Calculate the signature using:

   • SHA256.
   • The request body and secret key in binary.
     Make sure that the request body is as it is—don't deserialize it.

   Then base64-encode the result.

3. Compare the HmacSignature received from the header and the calculated signature. If the signatures match, then the notification was sent by Adyen and was not modified during transmission.

Here are some examples of how you would validate the HMAC signature.

import java.io.UnsupportedEncodingException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;
import javax.crypto.Mac;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
import org.apache.commons.codec.DecoderException;
import org.apache.commons.codec.binary.Base64;
import org.apache.commons.codec.binary.Hex;
import org.junit.Assert;
import org.junit.Test;

public class NotificationHmacExampleTest {

    @Test
    public void testNotificationHmac(){

        Base64 base64 = new Base64();
        try {

            // decode HEX Key into bytes
            byte[] keyBytes = Hex.decodeHex(hmacSignatureKey.toCharArray());

            // get payload in bytes
            byte[] payloadBytes = payload.getBytes("UTF-8");

            // instantiate the MAC object using HMAC / SHA256
            Mac hmacSha256 = Mac.getInstance(protocol);

            // create a key object using the secret key and MAC object
            SecretKey secretKey = new SecretKeySpec(keyBytes, hmacSha256.getAlgorithm());

            // initialise the MAC object
            hmacSha256.init(secretKey);

            // finalize the MAC operation
            byte[] signedPayload = hmacSha256.doFinal(payloadBytes);
            // encode the signed payload in Base64
            byte[] encodedSignedPayload = base64.encode(signedPayload);
            System.out.println("original HMAC signature: " + hmacSignature);
            System.out.println("computed HMAC signature: " + new String(encodedSignedPayload, "ASCII"));

            // assert the calculated Base64 encoded HMAC is equal to the received Base64 encoded HMAC
            Assert.assertTrue(Arrays.equals(encodedSignedPayload, hmacSignature.getBytes("UTF-8")));

        } catch (NoSuchAlgorithmException e) {
            // HmacSHA256 should be supported
        } catch (UnsupportedEncodingException e) {
            // UTF-8 should be supported
        } catch (DecoderException e) {
            // Check key for odd number or characters outside of HEX (base16)
        } catch (InvalidKeyException e) {
            // The key is invalid
        }
    }
}

import hmac
import hashlib
import base64

def checkHmac(payload, hmac_key, hmac_sig):
  # payload is the request body as it is
  # hmac_key is the secret
  # hmac_sig is the signature from the header
  hmac_key = binascii.a2b_hex(hmac_key)
  # Calculate signature
  calculatedHmac = hmac.new(hmac_key, payload.encode('utf-8'), hashlib.sha256).digest()
  calculatedHmac_b64 = base64.b64encode(calculatedHmac)

  receivedHmac_b64 = hmac_sig.encode('utf-8')
  validSignature = hmac.compare_digest(receivedHmac_b64, calculatedHmac_b64)

  if not validHMAC:
      print('HMAC is invalid: {} {}'.format(receivedHmac_b64, calculatedHmac_b64))
      return False

  return True

Accept notifications

When you are already receiving webhooks, Adyen requires that you respond to every notification. This is to ensure that your server is properly accepting notifications.

If we don't receive a response within 10 seconds, for example because your server is down, all notifications to your endpoint will be queued and retried.

To respond, send a HTTP 200 OK with [accepted] in the response body.

Adyen domain and IP addresses

Depending on your network and security requirements, you might need to add our network to your firewall's whitelist to receive webhooks.

We do not provide a list of IP addresses. IP addresses change over time due to various reasons, for example, ISP configuration changes. This can lead to disruptions in receiving notification webhooks if IP addresses are hard-coded.

To make sure you can communicate with our network, you can either:

• Use a domain allowlist. Include our domain out.adyen.com if your network configuration allows domain allowlisting.
• Systematically resolve our IP addresses. Perform DNS lookup for out.adyen.com. We recommend that you check every hour. However, if you choose to hardcode the resolved IP addresses to a whitelist, you still run the risk of a disruption if IP addresses change during the DNS lookup interval.