DNA Helix Loader
Two strands of dots weave past each other, shrinking as they pass behind and growing as they come to the front. Eight columns, two pseudo-elements each, no SVG.
Also known as: double helix animation, DNA strand loader.
HTML
<div class="ldr-dna-helix" role="status" aria-label="Loading"> <span></span><span></span><span></span><span></span> <span></span><span></span><span></span><span></span> </div>
CSS
.ldr-dna-helix {
--s: var(--ldr-size, 48px);
--c: var(--ldr-color, #3b82f6);
display: flex;
gap: calc(var(--s) / 10);
height: var(--s);
}
.ldr-dna-helix span {
position: relative;
width: calc(var(--s) / 10);
height: 100%;
}
.ldr-dna-helix span::before,
.ldr-dna-helix span::after {
content: "";
position: absolute;
top: 0;
left: 0;
width: 100%;
aspect-ratio: 1;
border-radius: 50%;
background: var(--c);
animation: ldr-dna-helix-weave 1.6s ease-in-out infinite;
animation-delay: var(--d, 0s);
}
.ldr-dna-helix span::after {
background: color-mix(in srgb, var(--ldr-color, #3b82f6) 50%, transparent);
animation-delay: calc(var(--d, 0s) - 0.8s);
}
.ldr-dna-helix span:nth-child(2) { --d: -0.15s; }
.ldr-dna-helix span:nth-child(3) { --d: -0.3s; }
.ldr-dna-helix span:nth-child(4) { --d: -0.45s; }
.ldr-dna-helix span:nth-child(5) { --d: -0.6s; }
.ldr-dna-helix span:nth-child(6) { --d: -0.75s; }
.ldr-dna-helix span:nth-child(7) { --d: -0.9s; }
.ldr-dna-helix span:nth-child(8) { --d: -1.05s; }
@keyframes ldr-dna-helix-weave {
0%, 100% { transform: translateY(0) scale(1); }
25% { transform: translateY(calc(var(--s) * 0.45)) scale(0.55); }
50% { transform: translateY(calc(var(--s) * 0.9)) scale(1); }
75% { transform: translateY(calc(var(--s) * 0.45)) scale(1.25); }
}
@media (prefers-reduced-motion: reduce) {
.ldr-dna-helix, .ldr-dna-helix *, .ldr-dna-helix::before, .ldr-dna-helix::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.