Video Buffering Progress Bar
A video scrubber: the buffered range jumps ahead in chunks while the played range and its knob follow at a steady speed, stalling whenever they catch up. Good for media and download UIs.
Also known as: video player progress bar, buffer progress bar, youtube style buffering bar.
HTML
<div class="ldr-buffering-progress-bar" role="progressbar" aria-label="Buffering"><span></span></div>
CSS
.ldr-buffering-progress-bar {
--s: var(--ldr-size, 48px);
--c: var(--ldr-color, #3b82f6);
--w: calc(var(--s) * 6);
position: relative;
width: var(--w);
height: calc(var(--s) / 10);
border-radius: var(--s);
background: color-mix(in srgb, var(--ldr-color, #3b82f6) 16%, transparent);
}
.ldr-buffering-progress-bar::before,
.ldr-buffering-progress-bar::after {
content: "";
position: absolute;
inset: 0;
border-radius: inherit;
transform-origin: left;
}
.ldr-buffering-progress-bar::before {
background: color-mix(in srgb, var(--ldr-color, #3b82f6) 36%, transparent);
animation: ldr-buffering-progress-bar-buffer 6s infinite;
}
.ldr-buffering-progress-bar::after {
background: var(--c);
animation: ldr-buffering-progress-bar-play 6s linear infinite;
}
.ldr-buffering-progress-bar span {
position: absolute;
top: 50%;
left: calc(var(--s) / -7);
width: calc(var(--s) / 3.5);
height: calc(var(--s) / 3.5);
margin-top: calc(var(--s) / -7);
border-radius: 50%;
background: var(--c);
box-shadow: 0 0 0 calc(var(--s) / 14) color-mix(in srgb, var(--ldr-color, #3b82f6) 22%, transparent);
animation: ldr-buffering-progress-bar-knob 6s linear infinite;
}
@keyframes ldr-buffering-progress-bar-buffer {
0% { transform: scaleX(0.04); animation-timing-function: cubic-bezier(0.2, 0.7, 0.3, 1); }
4%, 24% { transform: scaleX(0.32); animation-timing-function: cubic-bezier(0.2, 0.7, 0.3, 1); }
28%, 44% { transform: scaleX(0.58); animation-timing-function: cubic-bezier(0.2, 0.7, 0.3, 1); }
49%, 66% { transform: scaleX(0.86); animation-timing-function: cubic-bezier(0.2, 0.7, 0.3, 1); }
69%, 92% { transform: scaleX(1); opacity: 1; }
100% { transform: scaleX(1); opacity: 0; }
}
@keyframes ldr-buffering-progress-bar-play {
0% { transform: scaleX(0); }
18%, 26% { transform: scaleX(0.3); }
41%, 47% { transform: scaleX(0.55); }
64%, 68% { transform: scaleX(0.83); }
78%, 92% { transform: scaleX(1); opacity: 1; }
100% { transform: scaleX(1); opacity: 0; }
}
@keyframes ldr-buffering-progress-bar-knob {
0% { transform: translateX(0); }
18%, 26% { transform: translateX(calc(var(--w) * 0.3)) scale(1.2); }
41%, 47% { transform: translateX(calc(var(--w) * 0.55)) scale(1.2); }
64%, 68% { transform: translateX(calc(var(--w) * 0.83)) scale(1.2); }
78%, 92% { transform: translateX(var(--w)); opacity: 1; }
100% { transform: translateX(var(--w)); opacity: 0; }
}
@media (prefers-reduced-motion: reduce) {
.ldr-buffering-progress-bar, .ldr-buffering-progress-bar *, .ldr-buffering-progress-bar::before, .ldr-buffering-progress-bar::after, .ldr-buffering-progress-bar *::before, .ldr-buffering-progress-bar *::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.