Adaptive Font Size Accessibility: A Cross-Media Diagnostic Model

Font size is a foundational but inconsistently addressed factor in accessible user experience (UX) design. Across web, mobile, print, slides, and signage, font size decisions are shaped by divergent standards and assumptions, often lacking a unified, context-sensitive framework. This paper synthesizes insights from accessibility guidelines, vision science, and UX research to propose a diagnostic model for evaluating font size legibility across media. The model introduces perceptual clarity as a functional outcome shaped by five core variables: media format, viewing distance, user visual characteristics, content criticality, and environmental conditions. Rather than prescribing fixed thresholds, the model supports adaptive, evidence-aligned sizing decisions responsive to situational demands. It aims to guide designers, evaluators, and policy actors toward more inclusive, interoperable, and context-aware typographic practices.