Paying with your phone seems to be all the rage these days. First you needed NFC, with the likes of Google Wallet, or Android Pay, and then Apple Pay. Then you needed a Samsung device to work its magnetic secure Transmission magic. Now, Walmart is launching its own mobile payment solution — Walmart Pay — which requires the Walmart app. It’s now available in more than 4,600 of Walmart’s locations nationwide.

It would seem a little too good to be true if it was just an app, but Walmart’s foray into the mobile payment wars isn’t like the other payment systems at all. No, you can’t use Walmart Pay at Starbucks. It only works at Walmart stores, and it’s really just a glorified QR (quick response) code reader.

The service is targeted mainly toward people who shop at Walmart a lot, and already use the app to do things like refill their prescription, compare prices on eligible purchases with stores in the area, and check the in-store inventory. According to Walmart, the number of Walmart Pay users now numbers north of 20 million, and 88 percent of the app’s transactions come from repeat users.

“Nearly half of our customers bought their online orders on a mobile device,” said Neil Ashe, president and CEO of Walmart Global eCommerce. “That’s double last year, and significantly higher than the industry average.”

Technically, Walmart Pay should work on any smartphone, but you need the Walmart app, which is only available on Android and iOS. You can add any major credit or debit card, prepaid card, or even a Walmart gift card.

Using it is pretty straightforward: Once you install the Walmart app and register your card, all you have to do when you reach the cashier is open the app and choose Walmart Pay, activate the camera, and scan the QR code that appears on the debit reader next to the cashier. You’ll get an electronic receipt once the payment goes through. The company says you can even pay half the bill with cash and the rest through Walmart Pay.

“It’s important to note that Walmart Pay is not about improving payment, just for payment’s sake,” said Daniel Eckert, senior vice president of Walmart. “It’s about how we can use payment to create a better shopping experience for our customers in our stores. Walmart Pay is just the beginning.”

Walmart’s not the only big-box store showing its commitment to a proprietary platform. Reuters reported in December that Target was developing its own mobile payments app — slated for release as soon as this year.

Originally published on 12-05-2015. Updated on 07-06-2016 by Kyle Wiggers: Added news of nationwide launch.