Supermarkets have become the most important provider of food products worldwide. However, empirical evidence about how consumers make their food purchase decisions in this environment is still scarce. The present field study aimed to: i) explore how people make their in-store food purchases, and ii) identify the information they search for when making those purchases. Consumers (n = 144) were intercepted when entering the facilities of three supermarkets in two Uruguayan cities. They were asked to wear a mobile eye-tracker while they made their purchases as they normally do. The great majority of the consumers bought at least one food product or beverage (92%) and, on average, examined products from 2.8 sections. In total, they investigated 37 categories within 13 self-service sections, corresponding to 26 categories of ultra-processed products. For 67% of the products, consumers went straight to the product they seemed to be looking for, grabbed it and put it in their shopping basket or cart, without making any comparison among products. A limited information search was observed. On average, consumers spent 22 s examining products within self-service sections and only 6.9 s were elapsed from the moment they grabbed a product until they put it in the shopping cart. These results provide empirical evidence of the habitual nature of supermarket food purchases in a context characterized by wide availability of ultra-processed products. Taken together, the findings suggest that policies and interventions aimed at reducing purchases of ultra-processed products should disrupt habitual decisions at the point of purchase. In this sense, policies targeted at introducing salient changes on food packages hold potential to disrupt food purchases and encourage consumers to establish new and more healthful food purchase habits. Copyright © 2020 Elsevier Ltd. All rights reserved.