prefers-reduced-motion
A CSS media query that detects whether the user has asked their operating system to reduce motion/animations. It lets sites respect that setting by dampening or turning off animations — important for people who get nauseous or disturbed by motion.
Background: large animations, parallax, zoom effects, and sweeping transitions can trigger nausea, dizziness, or migraines in people with vestibular conditions — and distract others. Operating systems have a "reduce motion" setting, and @media (prefers-reduced-motion: reduce) lets CSS react to it. Pattern: write the animations as usual, but in a prefers-reduced-motion: reduce block dampen or remove them (e.g. swap a large motion for a simple fade, or animation: none). Good practice: always respect the setting for non-essential animations; keep only motion that actually conveys meaning. It's a WCAG accessibility requirement. A good example of respecting the user's expressed preferences. Together with focus trap and ARIA, part of accessible web. Related to scroll snap and focus trap.