Interface Lab

Motion should be opt-in

Define animation only inside prefers-reduced-motion: no-preference, so newly added components are static by default.
MotionConditionally supportedPriority 5Applied in the lab

Sources

  • StandardW3C (2024)

    Interaction-triggered motion must be switchable off; opt-in motion provides that behavior by default.

    “Motion animation triggered by interaction can be disabled, unless the animation is essential to the functionality or the information being conveyed.”SC 2.3.3 (AAA)

In this lab

Homepage background transitions animate only under prefers-reduced-motion: no-preference; with reduced motion, color changes are immediate.

Priority

This is a standards requirement that can be silently violated; escaped animations can be counted automatically.

Experiments

Findings

Conditionally supported

With reduced motion emulated and all components triggered, the opt-out variant ran exactly one animation (a skeleton shimmer with an intentionally omitted override), while opt-in ran none at every repetition and tested width; without reduced motion both behaved identically. This holds only when new components follow the opt-in convention; the pattern prevents accidental omissions, not deliberate violations.