Supplement 1. Selection of items from the EU Kids online, Global Kids Online and Livingstone et al. (2017) versions on the online parental mediation dimensions of each questionnaire.

The only evaluation instrument used is the integrated and paired questionnaire for the evaluation of parental mediation strategies for children and families/guardians. This has been carried out by jointly analysing items from the available and recent versions of the EU Kids Online project (http://www.eukidsonline.net/) in its 2017 version (for children), Global Kids Online (http://globalkidsonline.net/) (children and legal guardians version) and from the work of Livingstone et al. 2017 (where only legal guardians are assessed). The construction process can be found in Annex/Supplement A/1. Although the items are very similar in each of the versions, there are some differences, both in the number of items that make up each dimension and in the response scales. The guiding principle has been to make a proposal of maximums that combines all the possible items of the three versions, with the exception of item 18 of restrictive mediation, which has not been included in the statistical analyses as it has a different response scale to the rest of the items of the dimension (See supplement 1). Thus, all items have been added to this version and paired for the child and family/guardian formulas