Animation and discomfort.
THE PROBLEM
Movement on screen causes genuine discomfort for some people: nausea, dizziness and disorientation.
Parallax scrolling, large transitions and autoplaying video are the common causes.
THE SYSTEM SETTING
Operating systems have a reduced motion preference. Browsers expose it to websites.
Respecting it is straightforward and rarely done.
WHAT TO DO
Provide a CSS rule that disables or reduces animation when the preference is set.
Any developer can implement this in minutes.
WHAT TO AVOID REGARDLESS
Autoplaying video with motion Content that moves while being read Parallax effects over large distances Flashing content, which can trigger seizures
THE FLASHING WARNING
Content flashing more than three times per second can cause seizures in susceptible people.
That is a serious harm, not a preference.
Avoid it entirely.
WHAT ANIMATION IS FINE
Small, purposeful transitions: a menu opening, a button responding.
Those aid understanding rather than causing difficulty.
TESTING
Enable reduced motion in your system settings and load the site.
