Today Google will begin rolling out its long-awaited Android Pay app—the second version of an NFC-based payment app that the company has launched.

Although Google announced the Android Pay API in May at its I/O Developer's Conference , a date for the app's consumer-facing launch remained elusive. Today, a Google representative told Ars that the app will roll out to consumers on the Google Play Store gradually over a few days. After that, features within Android Pay will be rolled out gradually, too. That is, everyone with an NFC-enabled Android phone running KitKat 4.4 or higher will be able to install Android Pay within a few days, but after installation, Android Pay will only let users tap-and-pay at brick-and-mortar stores. Android users won't be able to make in-app payments with Android Pay just yet.

Android Pay relies on Host Card Emulation (HCE), and with Android 6.0 Marshmallow, users will be able to authenticate payments with a fingerprint if they so choose. At launch, customers can use Android Pay in hundreds of thousands of chain stores, including McDonald's, Macy's, and Whole Foods. "Android Pay will support credit and debit cards from the four major payment networks—American Express, Discover, MasterCard and Visa—issued by many of the most popular US banks and credit unions," Google wrote in a statement.

Of course, this isn't Google's first time around the mobile payments block. Back in 2011, Google released Google Wallet, a first-of-its kind app relying on infrastructure built over the previous years by MasterCard to make NFC-based payments.

Google Wallet never saw widespread adoption, however, and there were lots of reasons for that. For the most part, people still found it easier to simply swipe with a traditional magnetic stripe card as they were paying for something at a checkout terminal. Also, vendor deployment was spotty (you couldn't guarantee that you'd find a terminal that both worked and accepted NFC in all stores, even in ones Google originally partnered with), and credit card issuers were reportedly nervous about allowing transactions through Google's app. On top of all this, telecom carriers bristled at Google's project and launched their own competing mobile payments app, originally called Isis (then renamed Softcard, then purchased by Google earlier this year).

But the past year has seen a resurgence in interest from various companies in getting people to pay for things with their smartphones. Apple Pay launched in October 2014, and the structure of that payment ecosystem seemed to offer considerable improvements over Google Wallet's setup. Apple Pay relied on tokenization—a concept standardized by MasterCard and Visa that involves issuing a one-time code when a card is read at a terminal. That code conceals the buyer's credit card information from the merchant's (often weak) system. Tokenization is supposed to reduce card fraud, and Apple leveraged that fact with card issuers, convincing the issuers to pay Apple a small percentage on every payment.

According to The Wall Street Journal, Google will be getting no such mobile payment kickback for purchases made through its Android Pay platform (though it's unclear how long Apple's arrangements will last, either). But, as is Google's wont, Android Pay is likely making money off of gathered transaction data. Google writes in a blog post on the topic, “As soon as you make a purchase, you’ll see a payment confirmation that shows where a given transaction happened, along with the merchant’s name and phone number.” The merchant's name isn't hidden from Google as it is on Apple's similar platform, although the company says that's good for consumers because it allows Google to provide a more detailed transaction history than Apple Pay users get. That way, “it’s easy to catch any suspicious activity,” Google writes.

Also, despite Google's transition to Android Pay for customer-to-merchant payments, Google Wallet will still be around. Google is re-launching Wallet to support peer-to-peer payments exclusively. Confusingly, current Wallet users will be able to use the old app to access Android Pay features through an update to Wallet. That means you can have two different Wallet apps sitting next to each other on your phone. Ars' Ron Amadeo explains that situation more in-depth here.

In all, although this rollout of the Android Pay app doesn't change too much—it's essentially a second version of a service that Google pioneered four years ago—Android Pay does seem like a much smarter, more viable deployment of Google's earlier idea.

”What we're really focused on is building a great platform,” a Google representative told Ars on Wednesday. “That's a big difference with our approach.”

”We prioritized our partnerships this time around,” the spokesperson added, saying that Google worked closely with a variety of issuers and card networks to build support for Android Pay. This was an issue for Google Wallet—Google's deployment of Wallet reportedly alienated issuers who tried to block Google from offering support for their cards, forcing Google to attempt a fix-all approach that involved issuing all Wallet users a “virtual card” that was essentially a prepaid card that users' real cards would load money to. In the complicated world of credit card payments, this reportedly meant that Google actually ended up losing money on every transaction through Google Wallet.

But the time of warring interests in mobile payments is ending. In a statement to Ars, Visa Executive Vice President of Innovation and Strategic Partnerships Jim McCarthy said that the card network was all aboard Google's Android Pay endeavor. “We are excited to be in lockstep with Google as they bring Android Pay to US Visa cardholders and continue to help move mobile payments to the mainstream,” McCarthy confirmed.

Issuers and card networks aren't the only pieces of the puzzle, either. Google's spokesperson also told Ars that the company plans to put even more effort into building a customer base for mobile payments through loyalty programs. (You won't find too much in the way of Google-sponsored loyalty programs in the Android Pay app at launch, though. Those loyalty programs will come later.) “[Android Pay is] not something, we know, that once we flip it on everyone will pay with their phones,” the spokesperson said. “Part of [the] ecosystem is creating incentives for users.”