The aim of the present work was to evaluate the influence of two front-of-pack nutrition information schemes (traffic-light system and Chilean warning system) on consumer purchase of ultra-processed foods in a simulated online grocery store.

Following a between-subjects design, participants completed a simulated weekly food purchase in an online grocery store under one of three experimental conditions: (i) a control condition with no nutrition information, (ii) a traffic-light system and (iii) the Chilean warning system. Information about energy (calories), sugar, saturated fats and salt content was included in the nutrition information schemes.

Participants were recruited from a consumer database and a Facebook advertisement.

People from Montevideo (Uruguay), aged 18–77 years (n 437; 75 % female), participated in the study. All participants were in charge of food purchase in the household, at least occasionally.

No significant differences between experimental conditions were found in the mean share of ultra-processed foods purchased by participants, both in terms of number of products and expenditure, or in the mean energy, sugar, saturated fat and salt content of the purchased items. However, the Chilean warning system decreased intended purchase of sweets and desserts.

Results from this online simulation provided little evidence to suggest that the traffic-light system or the Chilean warning system in isolation could be effective in reducing purchase of ultra-processed foods or improving the nutritional composition of the purchased products.