Custom Terminal App

Dear Square team,
Is it possible to develop a custom application running on a Square terminal?

Can Square hardware read and transfer Smartcard data to a custom server? In other words, use the terminal to perform APDU commands via NFC, on non-EMV cards, and use the Terminal API to carry the card data?

Can a system utilize Square hardware, while not using Square wallets?

Thanks a lot,

Hi @maximep welcome to the forums!

You cannot install a custom application on a Square Terminal. The Terminal API is meant to start transactions on a terminal device from a custom POS solution (calling the Terminal API), which would live on another device.

To clarify: Square hardware cannot be used for non-Square transactions, if that’s what you’re asking.

Hello @sjosey, thanks a lot for your answer.
It is clear about the custom app using the terminal API.

Do you confirm that the Square terminal can still be used to read non-EMV cards, for example, access cards using ISO 14443 protocol, and communicate with the custom POS solution via these terminal API?

Thanks and best wishes for the new year.

You can find all the supported cards here: The Terminal API will require you to use a Square account, though, to be clear. Your custom POS would call the CreateTerminalCheckout endpoint, which would tell the terminal device to be ready for the payment; the customer would use their card, and the terminal would handle the rest. You can set up webhooks to know if the payment was successful or not on your POS, if you choose.

I recently built an application on Square Terminal for contactless payments. I believe you can only pair your app with Square Terminal and not develop an entire application on it. For hardware-based issues, you can use supported hardware with your Square Retail point of sale to run your business. This gives you an all-in-one countertop solution. With the Square Stand, you can connect your iPad to a cash drawer, receipt printer, and barcode scanner to equip your business with a full POS setup. I believe this is how major Enterprise Application Development Services work with Square Terminal. There are several articles out there that can help you set up hardware from Square for Retail Free or Square for Retail Plus. Hope it works. Cheers