Participants received a questionnaire including 3 sets of images of food packaging, (brand blinded), categorized by food groups: 8 cookies, 7 breakfast cereals, and 7 ready-to-eat meals, but without front-of-pack nutritional label (in case the original Nutri-Score was displayed on the product, it was hidden by the investigators). They had the possibility to check the back-of-pack nutrition facts and ingredient information. First, they were asked which product they would intend to purchase in each category, and which product they thought to be the "healthiest". Then, participants were asked 1) to rank them according to their nutritional quality by identifying the first, the second and the third products with the best nutritional quality (in this order) and 2) to identify those that were ultra-processed.

Participants received a questionnaire including 3 sets of images of real food product packaging (brand blinded), categorized by food groups: 8 cookies, 7 breakfast cereals, and 7 ready-to-eat meals, with the Nutri-Score 2.0 displayed on the front-of-pack of each product. First, they were asked which product they would intend to purchase in each category, and which product they thought to be the "healthiest". Then, participants were asked 1) to rank them according to their nutritional quality by identifying the first, the second and the third products with the best nutritional quality (in this order) and 2) to identify those that were ultra-processed. Last, a series of questions evaluated how participants of this arm perceived the Nutri-Score 2.0 and whether they found it helpful.

Participants in the experimental arm can see, in case the product is ultra-processed, a black banner surrounding the Nutri-Score, with the word "ultra-transformé", meaning ultra-processed, and no black banner otherwise. Participants in the control arm had no label at all. The intervention (the Nutri-Score 2.0) was added on the packaging on the products included in the 3 sets of images that participants recieved via the questionnaire.

The answers of the participants on the corresponding questionnaire (via the NutriNet-Santé website) were expected to match the order according to which Nutri-Score ranks the 3 products (highest nutritional quality, second highest, third highest). In case of ex-æquos (i.e., two products having the same Nutri-Score), both were considered correct. Therefore, the number of correct answers for the nutritional dimension could range between 0 (no correct answers) to 9 (3 best products*3 food categories, all correct answers).

Participants were expected to identify all UPFs on the corresponding questionnaire (via the NutriNet-Santé website). For each product, the answer was considered correct if an UPF was identified as such by the participant (the gold standard being the presence of the black banner of the Nutri-Score 2.0, corresponding to the NOVA 4 "ultra-processed" definition), and a non-UPF was identified as such. Therefore, the number of correct answers for the food processing dimension could range between 0 (no correct answers) and 22 (correct answer for all 22 products).

Assessed with the question (in the corresponding questionnaire via the NutriNet-Santé website) : "Which of these products would you purchase more frequently?". This aimed to explore whether Nutri-Score 2.0 (the intervention) had an effect on the purchasing intentions.