Food systems have been recognised to play a major role in climate change and it was estimated that they contributed to 34% of total anthropogenic greenhouse gas emissions (GHGe) in 2015 (Crippa, 2021). A French study evaluated that food accounted for 24% of the carbon footprint of households (Barbier et al., 2019). The largest contributor of these emissions is agriculture since it represents more than two-thirds of the food system’s GHGe (Barbier et al., 2019). The remaining third of the GHGe is due to transportation, consumption, industrial processes and packaging. A recent study showed that even if we were to stop fossil fuel emissions, the GHGe from food systems would not allow to stay under the targeted 1.5°C increase in global temperatures (Clark et al., 2020) highlighting the importance of cutting down agricultural GHGe. It has also been shown that the structure of our diets can be modified to reduce their carbon footprint and remain within a “safe operating space for humanity” as modelled by planetary boundaries (Willett et al., 2019). In particular, the reduction of meat and dairy consumption and the increase of plant-based food consumption are major levers to reduce the environmental impact of our diets (Hedenus et al., 2014; Scarborough et al., 2014). In developed countries particularly, where meat and dairy consumption is high, a shift towards more plant-based diets has been advocated by scientists for its beneficial impacts on health and the environment (Willett et al., 2019). However, this shift may not be easily achieved by consumers (Hartmann & Siegrist, 2017). This can be explained by the fact that eating meat is associated with pleasure and has strong cultural, social and personal values in our societies (Macdiarmid et al., 2016). The reluctance to reduce meat consumption may also be associated with the lack of knowledge of the environmental footprint of meat (Hartmann & Siegrist, 2017; Macdiarmid et al., 2016). The underestimation of the GHGe of different types of foods, especially animal products, has been previously highlighted and was considered as a potential area for interventions (Camilleri, 2019). In line with this idea, studies have shown that consumers with a higher knowledge regarding the impact of human behaviours on climate change declared higher intentions to adopt environmentally-friendly behaviours (Truelove & Parks, 2012). Environmental labels on food products have been described as potential drivers of the choice of environmentally-friendly products, as they may increase consumers’ knowledge about the environmental impact of the food products allowing consumers to make more informed decisions when choosing food products (Camilleri, 2019). In addition, consumers wish to be informed about the environmental footprint of the products that they consume (Gadema & Oglethorpe, 2011). However, when presented with those labels, many consumers found them hard to understand and to use (Gadema & Oglethorpe, 2011). Yet, the use of an environmental label is directly linked to its understanding (Grunert et al., 2014). Thus, there is a need of a clear environmental label that conveys key information regarding the environmental impact of foods and that is easily understood by consumers. Interventional studies using gold-standard design (i.e., randomised controlled trials) in realistic food purchasing environments are needed to demonstrate the effect of environmental labels on food choices (Vyth et al., 2012). Supermarkets are key environments to test the effect of food labelling interventions since they represented roughly 70% of the total food sales in 2019 in France (Insee, 2019). Studies testing the effect of environmental labels on food choices carried out in realistic food purchasing settings, such as online supermarkets (Muller & Lacroix, 2019), real supermarkets (Pelletier et al., 2016; Vanclay et al., 2011; Vlaeminck et al., 2014) or restaurants (Brunner et al., 2018) are scarce. To our knowledge, only one randomised controlled trial, consisting in an online food shopping task for soups, tested the effect of an environmental label on food choices (Camilleri, 2019). We will conduct a 2-arm randomised controlled trial (with and without labels) to test the effects of an environmental label on food choices in a virtual supermarket. Participants will take part in two shopping tasks: 1/ selection of 3 products to prepare a home-made dish, and 2/ selection of a ready-to-eat dish. These two tasks will be repeated for two scenarios: 1/ participants will be asked to select the foods as they would do for a usual day (everyday scenario), and 2/ participants will be asked to select the foods for an environmentally friendly meal (environmentally-friendly scenario). This experimental design will allow to compare food choices in the presence vs. the absence of an environmental label and to investigate whether the label is informative and likely to help individuals to choose more environmental-friendly food options when explicitly asked to do so. In line with previous results showing that participants were more likely to choose pulses for a meal at a restaurant compared to a home-cooking scenario (Melendrez-Ruiz et al., 2019), we also hypothesise that it might be easier for a consumer to choose more environmentally friendly ready-to-eat dish than more environmentally friendly ingredients to cook it from scratch. On top of the lack of knowledge regarding the link between food systems and climate change, it has been emphasized that food choice motivations are key barriers for a shift towards more plant-based diets (Grunert et al., 2014). Many criteria are considered when purchasing foods and differ among consumers. In the French population taste, price and geographical origin of products are the key declared criteria influencing food choice (European Commission. Directorate General for Health and Food Safety, 2020). Environmental considerations such as the carbon footprint were poorly rated among food choice motives by UK supermarket shoppers (Gadema & Oglethorpe, 2011). Similarly, the environment was declared by only 15% of European respondents as an important driver influencing food choice (European Commission. Directorate General for Health and Food Safety. et al., 2020). An additional aim of the present study is to investigate the relationships between food choice motives and the effect of an environmental label on food choices.