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Terminal API

Learn about our Terminal API, including the endpoints and structure.

We don't recommend using Terminal API in combination with a classic POS library. In addition, you can't use Terminal API with older eVo terminal models. Refer to the overview of terminals that support Terminal API.

Our Terminal API is based on the nexo Retailer Protocol.

The Adyen Terminal API lets you make payments, issue refunds, collect shopper information, and perform other shopper-terminal interactions using a payment terminal supplied by Adyen.

Before you make any point-of-sale payments, it is important to understand how Terminal API works and how requests and responses are structured.

Enable Terminal API

Before you can use Terminal API in your test environment, you need to enable it:

  1. Log in to your test Customer Area.
  2. Go to In-person payments > Terminal settings and select Integrations.
  3. Select the option to Enable Terminal API.
  4. Select Save.

When you switch to your live environment, follow the same steps in your live Customer Area.

Use the correct endpoint

The endpoints you need to use, and how you authenticate requests depends on how your integration connects to the Adyen payments platform:

Local communications

If your integration uses local communications, API requests are made from a POS app directly to a terminal's IP address. The terminal listens for POST requests to /nexo on port 8443. For example, if your terminal has the IP address you would make API requests to:

If your integration uses Android devices and the POS app is installed on the terminal itself, you can send POST requests to either localhost or from that app.

Alternatively, if you assign a hostname to your terminal, you can make requests to the resolvable hostname of the terminal.

You should either use DHCP reservation for the terminal IP addresses, or manually configure static IP addresses. This helps to prevent connection issues when the terminal or your network reboots.

To protect local communications, you need to add Adyen's certificate to your POS app, and encrypt your messages.

Cloud communications

If your integration uses cloud communications, your POS app makes API requests to the Adyen payments platform. Our platform then forwards the request to the terminal.

The endpoint you need to use depends on two things:

  • Whether your integration will receive transaction results synchronously or asynchronously.
  • Whether you are making test transactions or live transactions.
Test endpoints - for all test transactions
Synchronous result: https://terminal-api-test.adyen.com/sync
Asynchronous result: https://terminal-api-test.adyen.com/async

When you are ready to go live, you need to switch to a live transaction endpoint. For the best performance, use an endpoint that is geographically closest to the location of your store. If you previously built an integration and are now repeating that in a new region, make sure to change the live endpoint to the one for the new region.

To prevent unnecessary latency, use the live endpoint that is geographically closest.

Live endpoints - Australia
Synchronous result: https://terminal-api-live-au.adyen.com/sync
Asynchronous result: https://terminal-api-live-au.adyen.com/async
Live endpoints - East Asia
Synchronous result: https://terminal-api-live-apse.adyen.com/sync
Asynchronous result: https://terminal-api-live-apse.adyen.com/async
Live endpoints - Europe
Synchronous result: https://terminal-api-live.adyen.com/sync
Asynchronous result: https://terminal-api-live.adyen.com/async
Live endpoints - US
Synchronous result: https://terminal-api-live-us.adyen.com/sync
Asynchronous result: https://terminal-api-live-us.adyen.com/async

Get your API key

You need to include an Adyen API key in the request header for:

To get an API key for your test environment:

  1. Log in to your Customer Area.
  2. Go to Developers > API credentials, and select the API credential username for your integration, for example ws@Company.[YourCompanyAccount].
  3. Under Server settings > Authentication select the API key tab.
  4. Select Generate API key.
  5. Select the copy icon and store your API key securely in your system.
  6. Select Save changes.

When you switch to your live environment, follow the same steps in your live Customer Area.

Add the value of the API key to the request header using the key: x-API-key

API structure

Our Terminal API communicates with the terminal using JSON messages. All requests and responses have the following message header-body structure:

  • Message header: identifies the type of transaction, the terminal being used, and unique transaction identifiers.
  • Body: a request or response object, depending on the type of transaction. For example, when you make a payment request this is a PaymentRequest object, and when you receive a payment response this is a PaymentResponse object.

The message header and body of Terminal API requests and responses are described in more detail below.


Each Terminal API request you make is contained in a SaletoPOIRequest object. In this, you need to provide a:

  • MessageHeader object.
  • Request body object corresponding to the type of transaction. For example, this is a PaymentRequest object when you are making a payment, or an InputRequest object when you are requesting shopper input.

Request MessageHeader

In each request MessageHeader, specify the following:

Name Required Type Description
ProtocolVersion -white_check_mark- String

Version of Adyen's Terminal API.

The current version is 3.0

MessageClass -white_check_mark- Enum This is almost always Service, but it can also be Device or Event. We will specify which MessageClass is required throughout our documentation.
MessageCategory -white_check_mark- Enum The type of transaction. For example, Payment for a payment request. We will specify which MessageCategory is required throughout our documentation.
MessageType -white_check_mark- Enum This is always Request.
ServiceID -white_check_mark- String Your unique ID for this request, consisting of 1-10 alphanumeric characters. Must be unique within the last 48 hours for the terminal (POIID) being used.
SaleID -white_check_mark- String Your unique ID for the system where you send this request from.
POIID -white_check_mark- String

The unique ID of the terminal that you send this request to. Format: [device model]-[serial number]. For example, P400‑123456789.

To find the POIID, see Get the terminal ID.

The example below shows the header for making a payment.


Request body

The values you need to include in the request body depends on the type of transaction you are making. We provide examples and reference information for each transaction type throughout our point-of-sale documentation.


Each terminal API response you receive is contained in a SaleToPOIResponse object, and includes a:

In a cloud integration that receives results asynchronously, you only receive an ok response from the Terminal API. The MessageHeader and response body are sent in an event notification instead.

Response MessageHeader

The MessageHeader you receive in the response echoes the values you provided in the request. The only exception is the MessageType, which is Response.

The following example shows the header you would receive in response to the example payment request provided above.


Response body

The values you receive in the response body depends on the type of transaction request you made. We provide examples and reference information for each transaction type throughout our point-of-sale documentation.

The response body will often include a unique transaction identifier, and data you can use to generate your receipts.

Transaction identifier

Every API request that creates a transaction or interacts with your money flow (such as a payment or refund) returns a unique transaction identifier in the POITransactionID.TransactionID:

This identifier contains two values, separated by a dot:

  • Tender reference: a unique value generated by the terminal for the transaction.
  • PSP reference: a unique alphanumeric value generated by the Adyen payments platform for the transaction.

    If you use Adyen for online payments or an omnichannel strategy, the PSP reference is the equivalent of the pspReference that you receive for transactions made online.

You should store each transaction identifier you receive, as you will need it to:

  • Make a refund.
  • Make a payment with acquired card details.
  • Identify the transaction in your Customer Area, or in reports generated by Adyen.

Transaction identifiers for offline payments

If your integration uses local communications, your terminals will be able to make Offline EMV and store-and-forward transactions. When you experience a network issue, an Approved payment will only generate a transaction identifier with the tender reference:

Once the terminal is able to connect to the internet again, the Adyen payments platform will process the payment and generate an alphanumeric PSP reference. The PSP reference and tender reference can be found in your Customer Area, and in reports generated by Adyen.

Receipt data

When you make a transaction such as a payment, the payment result contains a PaymentReceipt object. You can add the key-value pairs from this object to the receipt that you print, display, or email to your shopper.

For more information, see our receipts documentation.

Get the terminal ID

When you make a Terminal API request, you need to indicate which payment terminal you want to use. To do so, you populate the POIID field in the MessageHeader with the unique identifier of the payment terminal in the format [device model]-[serial number]. For example, P400‑123456789.

There are several ways to get the unique ID (POIID) of a payment terminal:

Get the serial number from the terminal

To construct the POIID of the payment terminal:

  1. Find the serial number of the payment terminal:
    • On the back of the payment terminal.
    • On the payment terminal screen under Settings > Device info.
  2. Take the device model, for example, P400, and combine it with the serial number.
  3. Add a dash between the device model and the serial number.
  4. Remove any dashes from the serial number.

Get the serial number from your Customer Area

In your Customer Area, go to In-person payments > Terminals and select the payment terminal.

Make an API call

If your integration uses cloud communications, you can get the terminal ID with an API call:

  1. Make a POST /connectedTerminals request, specifying your merchant account and optionally a store belonging to that merchant account.
  2. In the response, get the POIID from the uniqueTerminalIds array.
    This array contains a POIID for every terminal that has a live cloud connection and belongs to the specified merchant account or store.

Use a diagnosis request

If your integration uses local communications, you can get the terminal ID using a diagnosis request.

  1. Make a diagnosis request with a placeholder MessageHeader.POIID, for example xxxx-123456789.
    The request will fail.

  2. In the DiagnosisResponse, find the correct POIID inside the MessageHeader.
    This is the POIID of the terminal that you sent the diagnosis request to.

Use an Android function

For Android payment terminals with your app installed on the terminal:

  • Get the POIID of the terminal by calling the following function:

Next steps