Scroll Timeline Playground - Online Scroll‑Driven Animation
Create an animation that advances with scroll using animation‑timeline: scroll(). See the visual timeline editor. Modern CSS.
UD5 Toolkit
Generate a sleek, pure CSS scroll progress indicator — lightweight, customizable, and copy‑ready.
Scroll progress bars have become an essential UX pattern on modern websites. They give readers a clear sense of how much content remains, reducing bounce rates and improving engagement. Studies show that users are 37% more likely to finish reading an article when a visual progress indicator is present.
The concept is beautifully simple — a slim bar fixed to the top (or bottom) of the viewport that fills as the user scrolls. What makes it elegant is that it requires zero JavaScript in modern browsers, thanks to the new CSS animation-timeline property.
Introduced as part of the Scroll-Driven Animations specification, animation-timeline: scroll(root) lets you bind a CSS animation directly to the scroll position of the document. This means the browser handles everything natively — no event listeners, no requestAnimationFrame, no performance overhead.
Of course, browser support is still evolving. As of 2025, Chromium-based browsers (Chrome, Edge, Opera, Brave) fully support scroll-driven animations. Firefox has the feature behind a flag, and Safari support is in development. For production sites, a progressive enhancement approach is recommended — use the CSS-only method as the primary implementation, with a tiny JavaScript fallback for unsupported browsers.
The progress bar you see above this text is a live demonstration. Scroll down within this preview window and watch the bar grow. Try tweaking the settings on the left — change colors, height, position, and effects — and see the changes instantly.
Beyond the obvious UX benefit, progress indicators subtly encourage users to scroll further. They tap into the psychological principle of goal gradient effect — the closer people get to a goal, the more motivated they become to complete it. A progress bar makes "finishing the article" a tangible goal.
Additionally, for content-heavy websites, scroll progress bars serve as a non-intrusive navigation aid. They answer the silent question every reader has: "How much more is there?"
One of the biggest advantages of the CSS-only approach is performance. Traditional JavaScript-based progress bars require listening to the scroll event, which can fire hundreds of times per second. Without proper throttling, this can cause jank and hurt Core Web Vitals scores — especially the Interaction to Next Paint (INP) metric.
With animation-timeline, the browser's compositor handles everything off the main thread. The result is buttery-smooth 60fps animations that don't interfere with user interactions or page responsiveness.
Try customizing your progress bar now! Use the controls on the left to adjust colors, height, position, and special effects. The generated CSS code below updates in real-time — just copy and paste it into your project.
animation-timeline property. By setting animation-timeline: scroll(root), you can bind a @keyframes animation directly to the scroll position of the document root element.scaleX(0) to scaleX(1) animation tied to the scroll timeline will naturally progress as the user scrolls — no JavaScript required. The browser's compositor handles the animation off the main thread, ensuring smooth 60fps performance.animation-timeline: scroll().layout.css.scroll-driven-animations.enabled flag (expected to ship fully in an upcoming release).scroll event can cause jank if not properly throttled with requestAnimationFrame or IntersectionObserver. The pure CSS method is objectively superior for performance.
<style> tag in your <head>).<div class="scroll-progress"></div> element just inside your <body> tag.animation-timeline yet, consider adding a small JavaScript polyfill for graceful degradation.
Create an animation that advances with scroll using animation‑timeline: scroll(). See the visual timeline editor. Modern CSS.
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