About Scroll Animation Generator

Generate CSS scroll-triggered animation code with IntersectionObserver. Part of the DevTools Surf developer suite. Browse more tools in the Animation / CSS collection.

Use Cases

• Frontend developers adding scroll-reveal animations to sections
• Marketing sites building parallax and progressive disclosure effects
• Portfolio developers creating engaging scroll-driven storytelling
• Landing page developers implementing lazy-load animation patterns

Tips

• Set threshold to 0.2 to trigger when 20% of element is visible
• Use transform: translateY for smooth scroll-reveal effects
• Add rootMargin to trigger animations slightly before elements appear

Fun Facts

• The IntersectionObserver API was proposed by Google engineer Eric Bidelman and shipped in Chrome 51 in 2016, replacing costly scroll event listeners that caused jank.
• Before IntersectionObserver, scroll-triggered animations required listening to the scroll event — which fires up to 60 times per second, often causing the main thread to lag.
• The CSS scroll-timeline property, reaching browsers in 2023-2024, enables scroll-linked animations entirely in CSS without any JavaScript or IntersectionObserver.

FAQ

Does it use IntersectionObserver?

Yes — modern, performant. Far better than scroll-event listeners (which fire constantly). The tool generates both the CSS and the observer JS.

What effects are common?

Fade-in, slide-up, scale-in, rotate-in. Plus staggered lists (each item animates as it enters).

Can I use CSS scroll-driven animations?

Yes — toggle for the new `animation-timeline: scroll()` approach. Chrome/Edge 115+ support; Safari and Firefox catching up.

Accessibility?

The generated code respects prefers-reduced-motion — users who prefer stillness see content appear without animation.