For a visual change that should track scrolling continuously, use a CSS scroll-driven animation: a scroll() timeline follows a scroll container’s progress, while a view() timeline follows an element as it moves through a scrollport. Use position: sticky to pin an element, not as a general scroll-progress styling mechanism. Use JavaScript when the behavior needs logic that CSS timelines cannot express.
Which CSS property or technique should you use?
There is no single CSS property that handles every style change based on scrolling. The right choice depends on what should drive the effect:
- A style that changes continuously with scrolling: use a CSS scroll-driven animation timeline.
- An element that should stay pinned while the page moves: use
position: sticky. Sticky positioning controls layout; it does not itself expose scroll progress for animating other styles. - A behavior that starts when an element enters or leaves view: consider an intersection observer or a scroll-triggered animation, depending on whether you need JavaScript logic or a time-based animation.
CSS scroll-driven animations connect animation progress to scrolling rather than elapsed time. The MDN overview of scroll-driven animations describes the main timeline types and their use. The W3C Scroll-driven Animations specification defines mechanisms for driving animation progress from a scroll container; it is a Working Draft.
How CSS scroll-driven timelines work
A scroll-driven animation uses a timeline to determine how far an animation has progressed. Scroll backward and its progress can move backward too; scroll forward and it advances. That differs from a conventional animation, whose progress is based on time.
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Scroll progress timeline
A scroll progress timeline tracks a scroll container’s progress through its scroll range. This suits effects tied to the overall movement through a page or a particular scrolling region—for example, a decorative indicator that fills as the reader moves down a long article.
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View progress timeline
A view progress timeline tracks an element as it passes through a scrollport. It is useful when the animation should correspond to that element’s passage through the visible scrolling area, rather than the scroller’s overall progress.
Both timeline types build on CSS Animations and the Web Animations API. They express continuous progress declaratively; they are not simply another name for sticky positioning or for detecting that an element has crossed a threshold.
Scroll-driven versus scroll-triggered animation
The terms describe different behavior. A scroll-driven animation’s progress follows scrolling. A scroll-triggered animation starts or reverses an ordinary time-based animation when an element reaches a scroll position; its duration is not determined by how quickly the user scrolls. MDN explains this distinction in its scroll-driven animation guidance.
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One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware match| Approach | What causes the effect | How progress works | Typical role |
|---|---|---|---|
| Scroll progress timeline | Progress through a scroll container’s range | Tracks scroll progress | Visual indicator tied to a scroller’s overall movement |
| View progress timeline | An element’s passage through a scrollport | Tracks the element’s progress through that area | Visual effect associated with an element moving into or through view |
| Scroll-triggered animation | Reaching a scroll position | Time-based once started or reversed | An animation that plays when a scroll threshold is reached |
position: sticky |
Layout position relative to scrolling | Does not provide an animation timeline | Keeping an element pinned within its scrolling context |
| JavaScript scroll handling or IntersectionObserver | Scroll events or changes in intersection | Depends on the code and behavior implemented | Imperative logic or behaviors that the CSS timeline model cannot express |
When JavaScript is the better fit
Use JavaScript when you need imperative decisions, application state changes, or behavior that does not fit a CSS animation timeline. A scroll listener can inspect scrolling directly; IntersectionObserver can report changes in an element’s intersection with a root or viewport. Neither is itself a CSS scroll-driven timeline.
These approaches have different costs from declarative CSS. MDN cautions that main-thread rendering work can be blocked and make a page feel unresponsive or janky. Keep scroll-related JavaScript work limited, and choose an observer or CSS timeline when it expresses the needed behavior without extra event-driven logic.
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Respect reduced-motion preferences
Scroll-linked movement can be distracting or cause nausea for some people. If motion is decorative rather than necessary to understand or use the page, make sure the content remains clear when that animation is removed or reduced. MDN recommends accounting for prefers-reduced-motion and demonstrates disassociating an optional animation from its timeline when the preference is set.
For example, an optional effect can be disabled in a reduced-motion media query:
@media (prefers-reduced-motion: reduce) {
.scroll-effect {
animation-timeline: auto;
}
}W3C WAI’s Technique C39 describes using the reduced-motion media query to prevent interaction-triggered motion. It is an example technique for WCAG 2.2 Success Criterion 2.3.3, not a mandatory implementation recipe. A single CSS override also does not automatically resolve every accessibility concern; consider whether the movement is necessary and whether the experience remains understandable without it.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Check compatibility before relying on a timeline
Browser support can change, and the W3C specification remains a Working Draft. The sources cited here do not establish a complete browser-and-version support matrix, so check current compatibility data for your target browsers before making a timeline essential to the experience. Keep the content usable if the animation is unavailable, and avoid treating decorative motion as a requirement for accessing information.
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