Walmart has made the mobile payment app Walmart Pay available in more than 4,600 Walmart stores nationwide.

Announced in December, Walmart Pay is pitched as a free mobile-payments service for use in the retail giant's stores. It allows payments on Apple and Android devices with almost all major credit cards, debit cards, pre-paid cards, and even Walmart gift cards.

The service is void of near-field communication (NFC) compatibility, so users must go inside Walmart's mobile app and activate Walmart Pay in order to initiate and complete a purchase.

“The simplicity and ease of Walmart Pay comes not only from how it works, but also in how it’s been built,” said Daniel Eckert, senior vice president, services, Walmart U.S. “We made a strategic decision to design Walmart Pay to work with almost any smartphone and accept almost any payment type – even allowing for the integration of other mobile wallets in the future. The result is an innovation that will make the ease of mobile payments a reality for millions of Americans.”