Inset Shadow Fill Button: CSS Hover Effect

Inset Shadow Fill Button

The pill's outline is an inset box-shadow, and on hover its spread grows inward from every edge until it fills. No pseudo-elements and no extra markup: one property does it.

Also known as: box shadow fill hover, fill from edges button, no pseudo element fill.

Color Base size 16px Dark background Hold hover state

HTML

<button class="hfx-inset-shadow-fill">Subscribe</button>

CSS

.hfx-inset-shadow-fill {
  --c: var(--hfx-color, #3b82f6);
  position: relative;
  isolation: isolate;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5em;
  padding: 0.75em 1.75em;
  border-radius: 999em;
  font: 600 var(--hfx-size, 16px)/1.2 system-ui, sans-serif;
  white-space: nowrap;
  cursor: pointer;
  border: 0;
  background: transparent;
  color: var(--c);
  box-shadow: inset 0 0 0 2px var(--c);
  transition: box-shadow 0.45s cubic-bezier(0.65, 0, 0.35, 1), color 0.3s ease 0.12s;
}
.hfx-inset-shadow-fill:is(:hover, :focus-visible) {
  box-shadow: inset 0 0 0 1.5em var(--c);
  color: #fff;
}

@media (prefers-reduced-motion: reduce) {
  .hfx-inset-shadow-fill, .hfx-inset-shadow-fill *, .hfx-inset-shadow-fill::before, .hfx-inset-shadow-fill::after, .hfx-inset-shadow-fill *::before, .hfx-inset-shadow-fill *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}

Customizing this snippet

Color: set --hfx-color on the element or a parent. Currently previewing #3b82f6.
Base size: set --hfx-size. Every other dimension is in em, so the whole thing scales together. Currently previewing 16px.
Speed: change the duration on the transition or animation shorthand. Staggered delays are relative, so they keep their rhythm.
Reduced motion: the rule at the end of the CSS turns the motion off for people who asked their OS for less of it. Keep it.

Inset Shadow Fill Button

HTML

CSS

Customizing this snippet

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