Background and objectivesIncreased prevalence of obesity and its comorbidities has shown the need to implement social policies to help curb this trend. Nutritional risk factors are recognized as key drivers of obesity and other chronic diseases in Spain and in other Western countries. Front-of-package labels (FoPLs) are efficient tools to help consumers make healthier choices. To be useful in purchasing situations, consumers need to understand the information provided by FoPLs. The study objective was to assess objective understanding by consumers of five types of FoPLs, i.e. Health Star Rating system (HSR), Multiple Traffic Lights (MTL), Nutri-Score, Reference Intakes (RIs), and Warning symbol in Spain. MethodsIn 2018, 1000 Spanish participants were recruited and requested to rank three sets of label-free products (one set of three pizzas, one set of three cakes, and one set of three breakfast cereals) according to their nutritional quality in an on-line survey. Participants were then randomized to one of the five types of FoPLs, and were requested to rank the same sets of products again, this time with a given FoPL displayed on the package. Changes in ability to correctly rank products according to FoPLs were compared between both tasks using ordinal logistic regression. ResultsFor all three food categories, Nutri-Score performed significantly better, followed by MTL, the Warning symbol, HSR and RIs. ConclusionsNutri-Score emerged as the most efficient FoPL in conveying information on the nutritional quality of foods among Spanish consumers.