Square Line Chase Loader
A line one side long chases itself around a faint square track, speeding up along each edge and easing into the corners. Four bars share one clip-path keyframe, each rotated a quarter turn.
Also known as: border chase loader, square outline loader, line snake loader.
HTML
<div class="ldr-square-line-chase" role="status" aria-label="Loading"> <span style="--i: 0"></span><span style="--i: 1"></span><span style="--i: 2"></span><span style="--i: 3"></span> </div>
CSS
.ldr-square-line-chase {
--s: var(--ldr-size, 48px);
--c: var(--ldr-color, #3b82f6);
--t: calc(var(--s) / 10);
position: relative;
width: calc(var(--s) * 0.9);
height: calc(var(--s) * 0.9);
}
.ldr-square-line-chase::before {
content: "";
position: absolute;
inset: 0;
border: var(--t) solid color-mix(in srgb, var(--ldr-color, #3b82f6) 15%, transparent);
border-radius: calc(var(--t) / 2);
}
.ldr-square-line-chase span {
position: absolute;
top: 0;
left: 0;
width: 100%;
height: var(--t);
border-radius: calc(var(--t) / 2);
background: var(--c);
transform: rotate(calc(var(--i) * 90deg));
transform-origin: 50% calc(var(--s) * 0.45);
clip-path: inset(0 100% 0 0);
animation: ldr-square-line-chase-draw 2.4s cubic-bezier(0.65, 0, 0.35, 1) infinite;
animation-delay: calc(var(--i) * 0.6s - 2.4s);
}
@keyframes ldr-square-line-chase-draw {
0% { clip-path: inset(0 100% 0 0); }
25% { clip-path: inset(0 0 0 0); }
50%, 100% { clip-path: inset(0 0 0 100%); }
}
@media (prefers-reduced-motion: reduce) {
.ldr-square-line-chase, .ldr-square-line-chase *, .ldr-square-line-chase::before, .ldr-square-line-chase::after, .ldr-square-line-chase *::before, .ldr-square-line-chase *::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.