CSS keyframes live in the global scope. Always. This means the last matching keyframe name loaded wins, and it wins for every component using that name. In component-based architectures where build order shifts between local and production environments, this is a silent bug factory. Amit Sheen on Smashing Magazine documents the exact failure mode: two components both define a keyframe called `pulse`, the second definition overwrites the first, and `component-one` ends up running an animation it never asked for.
Sheen's fix is a single shared stylesheet called `kf-tokens.css` with a `kf-` prefix namespace on every keyframe. One `@keyframes kf-fade-in` declaration replaces what he found in one project: over a dozen separate fade-in definitions, all animating `opacity` from `0` to `1`. The tokens are built with CSS custom properties so they stay customizable without spawning new definitions. It mirrors how teams already handle color and spacing tokens, applied to motion.
The article is worth reading in full for the dynamic keyframe construction using custom properties, which is where the approach gets technically interesting. Sheen walks through building slide and other parameterized animations that adapt to context without breaking the single-source-of-truth model. The CodePen demos make the global scope collision concrete and reproducible.
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