# flackr/scroll-timeline

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_How this analysis was created: the description and tags below were written by an AI model that read this project's README and public documentation pages; stars, license and language come straight from the GitHub API. The model does not read the source code._

1,157 stars · 112 forks · JavaScript · Apache-2.0

## Links

- GitHub: https://github.com/flackr/scroll-timeline
- awesome-repositories: https://awesome-repositories.com/repository/flackr-scroll-timeline.md

## Description

Scroll-timeline is a JavaScript library and standards-based browser polyfill that implements scroll-driven animations and scroll timelines for environments lacking native platform support. It links web animations and CSS animations directly to the user's scroll position or element visibility instead of time, enabling fluid visual effects tied to page movement.

The library supports scroll-driven page effects such as scaling image dimensions, panning background positions across large visual elements, and revealing transitions between visual states progressively as the user scrolls. It also triggers dynamic element animations whenever an item enters or intersects the visible viewport.

Underlying architectural mechanisms handle document structure changes, schedule animation frame updates with the rendering pipeline, and map container scroll dimensions and bounding rectangles into a normalized timeline progress percentage. Standard style declarations and CSS variables are intercepted to evaluate scroll progress manually and attach calculated values directly to target element keyframe animations.

## Tags

### User Interface & Experience

- [Scroll Animations](https://awesome-repositories.com/f/user-interface-experience/scroll-animations.md) — Links web animations directly to the user's scroll position to create fluid, interactive visual effects tied to page movement.
- [Scroll-Based Property Interpolation](https://awesome-repositories.com/f/user-interface-experience/linear-interpolation-rendering/scroll-based-property-interpolation.md) — Performs mathematical mapping of container scroll dimensions and bounding rectangles into a normalized timeline progress percentage.
- [Scroll-Driven Animation Tools](https://awesome-repositories.com/f/user-interface-experience/scroll-driven-animation-tools.md) — Links element animations directly to the scroll offset so visual progress tracks page movement accurately. ([source](https://github.com/flackr/scroll-timeline#readme))
- [Dynamic Element Animation](https://awesome-repositories.com/f/user-interface-experience/component-utilities/animation-engines/dynamic-animation-controllers/dynamic-element-animation.md) — Triggers and controls dynamic animations whenever an item enters or intersects the visible viewport area. ([source](https://github.com/flackr/scroll-timeline#readme))

### Part of an Awesome List

- [Scroll Timeline Polyfills](https://awesome-repositories.com/f/awesome-lists/devtools/css-polyfills/css-polyfill-engines/scroll-timeline-polyfills.md) — Implements scroll-driven animations and scroll timelines for web browsers lacking native platform support.
- [Scroll Animation Polyfills](https://awesome-repositories.com/f/awesome-lists/devtools/css-polyfills/scroll-animation-polyfills.md) — Provides a standards-based polyfill that enables CSS animations to be driven by scroll position instead of time.

### Graphics & Multimedia

- [Scroll-Driven Transition Effects](https://awesome-repositories.com/f/graphics-multimedia/custom-animation-effects/ui-transition-effects/scroll-driven-transition-effects.md) — Scales images, reveals content, and creates panoramic transitions that progress naturally as the user scrolls.