Neon Border: CSS Border Animation

Neon Border

A neon tube framing a dark panel, with a hot white core, a colored halo and light spilling onto the wall. It hums and blinks out for a beat now and then. Only opacity animates.

Also known as: css neon border, neon border animation, neon glow border css.

Open late

Color Base size 16px Dark background Hold hover state

HTML

<div class="bdr-neon-border"><span class="bdr-neon-border-text">Open late</span></div>

CSS

.bdr-neon-border {
  --c: var(--bdr-color, #3b82f6);
  font-size: var(--bdr-size, 16px);
  position: relative;
  display: grid;
  place-items: center;
  width: 15em;
  height: 8.5em;
  border-radius: 1em;
  font-family: system-ui, sans-serif;
  font-weight: 600;
  --lit: color-mix(in srgb, var(--c) 35%, #fff);
  background: color-mix(in srgb, var(--c) 7%, #0a0a10);
  box-shadow: 0 0 1.4em color-mix(in srgb, var(--c) 22%, transparent);
  color: var(--lit);
}
.bdr-neon-border::before,
.bdr-neon-border::after {
  content: "";
  position: absolute;
  pointer-events: none;
  animation: bdr-neon-border-hum 5s linear infinite;
}
.bdr-neon-border::before {
  inset: 0.6em;
  border: 0.14em solid var(--lit);
  border-radius: 0.55em;
  box-shadow:
    0 0 0.15em var(--c),
    0 0 0.6em var(--c),
    0 0 1.3em color-mix(in srgb, var(--c) 55%, transparent),
    inset 0 0 0.15em var(--c),
    inset 0 0 0.7em color-mix(in srgb, var(--c) 50%, transparent);
}
.bdr-neon-border::after {
  inset: 0;
  border-radius: inherit;
  background: radial-gradient(closest-side, color-mix(in srgb, var(--c) 16%, transparent), transparent);
}
.bdr-neon-border-text {
  position: relative;
  font-size: 1.15em;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  text-shadow: 0 0 0.12em var(--c), 0 0 0.5em var(--c);
  animation: bdr-neon-border-hum 5s linear infinite;
}
@keyframes bdr-neon-border-hum {
  0%, 9%, 13.5%, 64%, 66%, 100% { opacity: 1; }
  10%, 12% { opacity: 0.3; }
  11%      { opacity: 0.95; }
  40%      { opacity: 0.92; }
  65%      { opacity: 0.55; }
}

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

Customizing this snippet

Color: set --bdr-color on the element or a parent. Currently previewing #3b82f6.
Base size: set --bdr-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.

Neon Border

HTML

CSS

Customizing this snippet

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