Digital coupons have become a normal part of grocery shopping, but using them is not always as simple as clipping a coupon from the Sunday paper. Shoppers may need a store account, a loyalty card, a smartphone app, and a few extra minutes before heading to the checkout. Some offers also come with purchase limits, specific sizes, expiration dates, or other restrictions that are easy to miss. Consumer Reports found that digital coupon use has grown while paper coupons have declined, with many retailers requiring customers to join loyalty programs to access digital discounts. The result is a system that can save money, but only if shoppers understand how it works.