SavingStar, a digital coupon and promotion program that offers deals and gathers individual shopper data across many retailers and brands, is expanding to 30,000 additional stores, including Walmart, Target, Walgreens, Dollar General and Family Dollar as of July 7.

The service, which launched more than two years ago and has 5 million members shopping at more than 100 grocery and drug chains, up to now has worked by linking to retailers' loyalty databases and scanners to track purchases.

But the expansion, which will more than double SavingStar coverage to 58,000 stores, involves mainly retailers who don't have standard loyalty cards. To do that, SavingStar is banking that it can get shoppers to use their smartphones and apps to scan receipts, a bet similar to the one Walmart is making as it simultaneously rolls out its own card-less version of a loyalty program.

Walmart has joined Target, Dollar General, Family Dollar, Meijer, WinCo and Walgreens to provide the necessary item-level data on their receipts so that people can verify they've actually bought products targeted by promotions, said SavingStar CEO David Rochon. Kmart, also being added to SavingStar coverage, is linking its loyalty card data like existing retail participants.

SavingStar works like a syndicated loyalty program that tracks individual shopper purchases across multiple retailers. For one of its more popular offers, dubbed "One or Many," people can buy multiple brand products over several weeks to qualify, e.g. "Spend spend $20 on Ziploc products over eight weeks at 'One or Many' stores over 'One or Many' shopping trips to get $5 back."

So adding data from big mass merchants, dollar and drug chains will provide far more chances for people to hit offer thresholds, plus much deeper data on shoppers that ultimately can be used to analyze purchase trends and tailor brand offers.

But that means relying on receipt scanning -- a habit few consumers have adopted and one some people doubt they will.

Michael Wohlschlaeger, CEO of Ahalogy, which optimizes brand programs for Pinterest and other social media, actually started his business a few pivots ago on the proposition of getting people to scan receipts for CPG marketing purposes before deciding it was impractical. Kurt Jetta, CEO of shopper analytics firm TABS, notes that it's been a challenge for Nielsen to ensure complete receipt-scanning compliance even for paid panelists.

Nevertheless, Walmart plans what Chief Marketing Officer Stephen Quinn said will be "a major focus in the back half of the year" on its receipt-based Savings Catcher program just as SavingStar will be pushing its members to scan receipts. Will shoppers be willing to do it, even entering data from the same receipt twice in the case of Walmart?

Mr. Rochon said only time will tell, though scanning receipts is ultimately easier than clipping, sorting and carrying coupons. His goal is to ultimately have enough members to replace the volume paper coupons generate.

Alvaro Serrano, senior marketing manager of Goya Foods, said he's had strong results from two SavingStar programs in getting people to "buy the Goya portfolio more deeply," and is hoping the expansion makes them work even better.

Brendan O'Marra, director-digital and promotion at Sun Products Corp., marketer of All, Wisk and Snuggle, is looking forward to the expansion of SavingStar, since "before, some of our largest customers like Walmart couldn't participate."

Even so, he's liked the ability to scale deals across multiple purchases of detergent and fabric softener and get data about how promotions changed shopper behavior across retailers. "You almost get a panel look," he said, which helps shape future shopper and geo-location marketing efforts.

Mr. O'Marra acknowledged some consumers may not be comfortable scanning receipts at first, but added: "I don't think it will be as long of a ramp up as some previously launched technologies."