Universal design requires that the design of systems, services, and environments support all types of users. This entry focuses on users with three types of disabilities: sensory, cognitive, and motor, and the need to consider their unique needs in design. Accessibility challenges are mainly in three areas: structures and navigations, information access and comprehension, and system features. Design recommendations corresponding to the accessibility barriers are also discussed. Future directions on this topic are further suggested in relation to comparing the needs of people with different impairments, creating one-size-fits-all systems, applying artificial intelligence, and designing systems in mobile environments.