Rainbow Border Button: CSS Button Style & Animation

Rainbow Border Button

A dark button with an RGB border that flows sideways like gaming gear, and a blurred rainbow glowing under it. The border is a second background clipped to border-box, moved one tile per loop.

Also known as: rgb button css, rainbow button css, gaming rgb border.

Color Base size 18px Dark background Hold hover state

HTML

<button class="btn-rainbow-border" type="button"><span class="btn-rainbow-border-face">Launch app</span></button>

CSS

.btn-rainbow-border {
  --c: var(--btn-color, #3b82f6);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5em;
  padding: 0.75em 1.6em;
  border: 0;
  border-radius: 0.6em;
  font: 600 var(--btn-size, 18px)/1.1 system-ui, sans-serif;
  cursor: pointer;
  -webkit-tap-highlight-color: transparent;
  --rgb: linear-gradient(90deg, #ff3d6e, #ff9f1c, #ffe14d, #3ddc84, #2ec5ff, #7c5cff, #ff3d6e);
  position: relative;
  isolation: isolate;
  padding: 0;
  border-radius: 0.75em;
  background: transparent;
  color: #fff;
  transition: transform 0.2s ease;}
.btn-rainbow-border::before {
  content: "";
  position: absolute;
  top: 45%;
  right: 10%;
  bottom: -0.3em;
  left: 10%;
  z-index: -1;
  background: var(--rgb) 0 0 / 14em 100%;
  filter: blur(0.8em);
  opacity: 0.7;
  animation: btn-rainbow-border-glow 3s linear infinite;
  transition: opacity 0.3s ease;
}
.btn-rainbow-border-face {
  display: block;
  padding: 0.8em 1.8em;
  border: 2px solid transparent;
  border-radius: inherit;
  background:
    linear-gradient(color-mix(in srgb, var(--c) 16%, #0c0f16), color-mix(in srgb, var(--c) 16%, #0c0f16)) padding-box,
    var(--rgb) 0 0 / 14em 100% border-box;
  animation: btn-rainbow-border-flow 3s linear infinite;
}
.btn-rainbow-border:is(:hover, :focus-visible)::before { opacity: 1; }
.btn-rainbow-border:active { transform: scale(0.97); }
@keyframes btn-rainbow-border-flow {
  to { background-position: 0 0, 14em 0; }
}
@keyframes btn-rainbow-border-glow {
  to { background-position: 14em 0; }
}

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

Customizing this snippet

Color: set --btn-color on the element or a parent. Currently previewing #3b82f6.
Base size: set --btn-size. Every other dimension is in em, so the whole thing scales together. Currently previewing 18px.
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.

Rainbow Border Button

HTML

CSS

Customizing this snippet

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