Inclusive Design Accessibility is the practice of building digital products that work for everyone, including people with disabilities (visual, motor, cognitive, hearing), users on slow networks, and those using assistive technologies like screen readers or voice control. It's guided by Web Content Accessibility Guidelines (WCAG 2.1), a W3C standard that defines testable criteria across four principles: Perceivable, Operable, Understandable, Robust. Mastery means understanding these standards deeply and knowing how to test, implement, and iterate with real users.