We study retailer app use and shopping behavior by investigating whether and how app adopters’ preferred store registration (PSR), a voluntary enrollment of store loyalty program, can lead to changes in purchase behaviors among the adopters in offline stores. A panel dataset from a large bakery franchise chain was studied using difference-in-differences with propensity score matching for causal inference. The results show that customers who participated in PSR increase their spending, compared to customers who did not. In addition, the results confirm that the PSR-spending relationship is moderated by customer and store characteristics; customers who visited infrequently and spent less prior to PSR participation increase their purchases, and they spend more at stores with better service quality.