Digital competencies have become a cross-cutting prerequisite for participation in the labor market, access to public and private services, and the autonomous exercise of citizenship in highly digitalized sociotechnical environments. Despite their growing importance, these competencies are still frequently measured using self-reported instruments, whose validity may be limited when respondents have only an incomplete understanding of the underlying digital mechanisms. This reliance on self-reported measures raises an important methodological concern: individuals may overestimate their competence when familiarity with digital tools is mistaken for an actual understanding of how those tools function. This study formally assesses three fundamental dimensions of digital competence—understanding of data, processing, and architecture—and compares these objective measures with participants' self-assessments in order to examine the gap between perceived and measured competence.