SAN FRANCISCO — Amazon is expanding technology to let shoppers pay by scanning their palm print to several Whole Foods stores in Seattle, aiming to push it to a broader group of patrons.

The technology, called Amazon One, works by scanning a palm print and connecting it to a credit card. After that, a shopper holds their palm above a sensor to pay for groceries or books.

Amazon previously said it plans to sell the service to retailers, stadiums and office buildings, and the Whole Foods rollout will be its first attempted push to a more mainstream audience. But the palm-scanning technology immediately raised privacy concerns when Amazon unveiled it last year, and experts said it was unclear whether customers would feel comfortable using it.

Amazon insists it keeps palm scans encrypted in a safe corner of its cloud, but experts still worry the technology could be a security risk.

Amazon said in a blog post Wednesday that the data is protected by “multiple security controls” and never stored on the devices, which are placed in stores so anyone can sign up.

Amazon CEO and founder Jeff Bezos owns The Washington Post.

Amazon One is a response, in many ways, to biometric payment technology that already exists on smartphones. Apple, for example, will scan your face to unlock your stored credit card. But the difference with Amazon is that the palm prints will be sent and secured in a server, rather than remaining solely on the device.

The introduction of the palm-scanning technology is part of Amazon’s push to make shopping in real life more like buying things with one click online — a method that retail analysts call reducing friction and that typically results in customers spending more. The palm print can also be linked to customers’ Amazon Prime accounts, providing data on how people shop and browse in real life.

Amazon debuted the technology last year and rolled it out at the company’s small stores in its hometown Seattle, including its Go cashier-less convenience stores and its bookstore. But its introduction at Whole Foods signals that Amazon intends the technology to expand to a mainstream group of shoppers.

For now, the tech is live at just one Whole Foods store — the location on Madison Street and Broadway in Seattle. Amazon said it will bring it to seven more Whole Foods stores in the Seattle area.

Amazon is known for packing its physical retail stores full of technology. It’s small-size Go stores use computer vision technology to track shoppers through the stores so they can walk out with their items without stopping at a cash register. The shopping baskets are then charged to their Amazon accounts.

And the company’s brick-and-mortar bookstores give it ample space to show off its higher-priced tech items, including Kindles and Echo smart speakers.

On Tuesday, Amazon said it was opening a hair salon in London.