This chapter describes the contextual information collected during the International Computer and Information Literacy Study (ICILS) 2023 in order to aid understanding of variation in the primary outcome achievement measures of the study: students’ computer and information literacy (CIL) and computational thinking (CT). Both outcome measures may be potentially influenced by a given set of contextual information. We provide a classification of contextual factors that accords with the multilevel structure inherent in the process of student CIL/CT learning. The learning of individual students happens in the overlapping contexts of school learning and out-of-school learning, both of which are embedded in the context of the wider community that comprises local, national, supranational, and international contexts. We distinguish between four contexts: wider community, schools and classrooms, home environment and the individual. In addition, we consider the relationship of these contextual factors to the learning process (antecedents or processes). We also list the different kinds of variables that are collected via the different ICILS 2023 contextual instruments and briefly outline prior findings from educational research in order to explain why these variables are included in ICILS 2023.