This chapter introduces the International Computer and Information Literacy Study (ICILS) 2023 and its role in assessing students’ digital literacy in the context of rapid technological change. The chapter highlights the importance of advanced skills in evaluating, producing, and communicating information digitally, emphasizing their relevance for education, work, and civic engagement. The chapter describes the assessments of computer and information literacy (CIL) and computational thinking (CT) achievement in ICILS 2023, with reference to the ICILS 2023 Assessment Framework, and situates these outcomes in the within- and out-of-school contexts in which CIL and CT learning takes place. The chapter summarizes the ICILS 2023 research questions with specific reference to the variations in CIL and CT within and across countries, the relationships between CIL and CT achievement and student background characteristics, the role of education systems, schools, and teaching practices in supporting the development of student CIL and CT, and changes in CIL and CT achievement across the cycles of ICILS. Additionally, the chapter explains the rigorous methodology implemented in ICILS, including its test and questionnaire instruments and procedures for collecting internationally comparable data. This foundation provides evidence to support policy and practice aimed at enhancing digital literacy education globally.