Suddenly, they're popping up everywhere -- those square, futuristic-looking matrixes that appear to be a cross between abstract art and Rorschach tests.
You'll find them in the corner of newspaper and magazine ads, in department store aisles, on product displays, price tags and For Sale signs in front of homes. Giant-size versions have shown up on billboards.
Called quick response codes, or simply QRs, they're the barcodes for the digital age -- but ones that convey far more information and can be scanned by consumers with smart phones and tablet computers to open a Web page, play a video or even place a call.
The technology has been around for years, but only recently has it been embraced by U.S. retailers and other companies looking for fresh ways to connect with customers. The number of QR scans recorded by the industry's leading code maker has soared to 2 million a month, nearly double the rate last year, and up from 80,000 a month in 2009.
"Advertisers are regarding them as the hottest new tool of mobile advertising," said Colin Gibbs, an analyst at research group GigaOm Pro. "They love QRs because they're cheap and easy to deploy, and you can put them anywhere from print ads to the back of stadium seats."
Macy's Inc. has QRs displayed throughout its stores, with signs giving step-by-step instructions on how they're used. Shoppers who aim their smart phones' cameras at the codes get videos on their phone screens of makeup guru Bobbi Brown dispensing application tips or Martha Stewart dishing out decorating advice.
Customers at Home Depot get on-the-spot access to how-to guides and videos. Miller Beer put QRs on Lite beer cans for a summer promotion. Gap Inc., Target Corp., Starbucks Corp. and Ford Motor Co. have used them in advertising.
Real estate company RE/MAX International uses QRs to give prospective homebuyers information not only about a house, but also neighborhoods and local schools.
QRs were invented in the mid-1990s in Japan, where smart phones gained early acceptance and where companies such as McDonald's Corp. have long stamped them on hamburger wrappers.
Their widespread adoption in the U.S. has paralleled the growth of smart phones and tablets with high-quality cameras and apps; Nielsen Co. projects that about half of all Americans will own smart phones by year's end.
Consumer awareness still lags behind. Only 5 percent of total smart phone owners in the U.S. have scanned a QR, according to Forrester Research. But it's on a sharp curve upward. About 25 percent of Android phone owners and 7 percent of iPhone users tried out a QR in the second quarter of 2010, and that number is expected to rise this year, Forrester said.
Still, QRs remain a mystery to many -- including some who grew up in the digital age.
Identical twins Matt and Adam Rinne, 32, were puzzling over the squares on a recent afternoon at a Best Buy in Burbank, Calif. Most of the higher-priced gadgets in the store, including laptops and cameras, had codes stamped onto their tags.
"I've seen these things everywhere," said Adam, who, like his brother, is a personal trainer. "I consider myself somewhat tech savvy, and I still have no idea what they are."
Home Depot, which began putting QRs in stores and on ads in March, is betting that people will soon learn.
"This is where other large retailers are heading," said Tom Sweeney, senior director for online strategy at the home improvement chain. "We wanted to make sure we were in line with the retail world. It's definitely coming into its own and becoming a more prevalent way for retailers to connect broadly and engage with customers."
For privacy advocates, however, QRs are one more source of concern. That's because the codes don't just impart information, they can also collect data on where and when a QR was scanned. They can, in some cases, even latch onto the phone user's name, age and other personal information.
"Theoretically, over time companies can build up their database and amass a collection of information that leads to a profile of who I am and what I buy," said Julie Ask, a mobile marketing analyst at Forrester.
The digital cognoscenti don't appear to be concerned. For now, knowing how to break the QR code is akin to being a member of a hip underground club.
Lady Gaga has partnered with Starbucks for a promotion that's triggered by scanning QRs on signs in the coffee shops. Some trendy bars are putting them on drink glasses. Using free sites that generate the codes, some people have put QRs on business cards, which are linked to their Facebook pages, resumes or contact information.