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Walmart shoppers from California to Maine and everywhere in between can now use their phone make purchases at the cash register.

The nation's largest retail chain said on Wednesday that Walmart Pay, the retailer's mobile payment system, is now available in the entire US. Walmart Pay is in all 4,600 stores in the country and can be accessed through the retailer's app on iOS or Android, which boasts over 20 million users. The company promises the payment system will make your Walmart checkout experience as efficient as possible.

"It's also about saving time and time is a new currency for a busy family," said Daniel Eckert, senior vice president of services, in a conference call with reporters.

Walmart Pay's expansion comes as more consumers are starting to use mobile payment systems like Apple Pay and Android Pay, which let your phone double as a wallet. Unlike the other phone pay options, Walmart Pay only works at its own locations. The retailer also doesn't accept any other type of mobile payment system.

Walmart Pay works through a QR (short for quick response) code system. When you're ready to pay, you pull up the retailer's app, enter a PIN and scan the matrix bar code presented to you at the register with your total. Your receipt is sent to the app directly.

That differs from Android Pay and Apple Pay, which use a near-field communications, or NFC, chip to let you tap your phone at an NFC-enabled register to make a payment. Samsung Pay uses a combination of NFC as well as a proprietary tech that works with older registers.

Walmart is the only retailer with a proprietary mobile payment system and its platform supports all major debit and credit cards, as well as prepaid and Walmart gift cards.

"Walmart Pay is just the beginning of new things to come from us," Eckert said.