Knight Rider Scanner Loader
A glow slides back and forth along a row of LED segments, the 80s car scanner look. The segments are a repeating-gradient mask, so one moving pseudo-element lights all of them.
Also known as: larson scanner, cylon eye loader, back and forth light bar.
HTML
<div class="ldr-knight-rider-scanner" role="status" aria-label="Loading"></div>
CSS
.ldr-knight-rider-scanner {
--s: var(--ldr-size, 48px);
--c: var(--ldr-color, #3b82f6);
--p: calc(var(--s) / 4.4);
--g: calc(var(--s) / 18);
position: relative;
overflow: hidden;
width: calc(var(--p) * 8 - var(--g));
height: calc(var(--s) / 3.2);
background: color-mix(in srgb, var(--ldr-color, #3b82f6) 16%, transparent);
-webkit-mask: repeating-linear-gradient(90deg, #000 0 calc(var(--p) - var(--g)), transparent 0 var(--p));
mask: repeating-linear-gradient(90deg, #000 0 calc(var(--p) - var(--g)), transparent 0 var(--p));
}
.ldr-knight-rider-scanner::before {
content: "";
position: absolute;
top: 0;
bottom: 0;
left: 0;
width: calc(var(--p) * 3);
background: linear-gradient(90deg, transparent, var(--c) 38% 62%, transparent);
animation: ldr-knight-rider-scanner-sweep 0.8s cubic-bezier(0.45, 0, 0.55, 1) infinite alternate;
}
@keyframes ldr-knight-rider-scanner-sweep {
from { transform: translateX(calc(var(--p) * -1)); }
to { transform: translateX(calc(var(--p) * 6)); }
}
@media (prefers-reduced-motion: reduce) {
.ldr-knight-rider-scanner, .ldr-knight-rider-scanner *, .ldr-knight-rider-scanner::before, .ldr-knight-rider-scanner::after, .ldr-knight-rider-scanner *::before, .ldr-knight-rider-scanner *::after {
animation-duration: 3s;
}
}Customizing this loader
- Color: set
--ldr-coloron the element or a parent. Currently previewing#3b82f6. - Size: set
--ldr-size. Every dimension in the snippet is derived from it. Currently previewing64px. - Speed: change the duration on the
animationshorthand. Delays on the children are relative, so they keep their rhythm. - Accessibility: the root carries
role="status"and anaria-labelso screen readers announce the wait. The reduced-motion rule at the end slows the animation for users who asked for less motion.