Non-Functional Requirement

A software requirement that specifies how a system should behave rather than what it should do. Non-functional requirements include accessibility, security, performance, maintainability, and usability. In web development, accessibility is a critical non-functional requirement that is frequently overlooked because developers and AI coding tools tend to focus on functional correctness—whether the code produces the right output—while neglecting whether the output is perceivable, operable, understandable, and robust for all users. Researchers have advocated treating accessibility as an integral non-functional requirement in UI/UX documentation, on par with security and privacy.