gsap

name	gsap
description	GSAP animation engine sub-skill - core, timeline, ScrollTrigger, plugins.

GSAP — Animation Engine

When to use GSAP

Criteria	CSS Transitions	Framer Motion	GSAP
Hover / simple toggle	Yes	Yes	Overkill
Sequenced timeline	No	Limited	Yes
Scroll-driven	scroll-timeline	Limited	ScrollTrigger
Complex stagger	No	Basic	Distribution
Mobile perf (60fps)	Good	Average	Excellent
Text splitting	No	No	SplitText
SVG morph / draw	No	No	MorphSVG
Bundle size concern	0kb	~30kb	~25kb + plugins

Rule: if the animation needs timeline, scroll-link, or distributed stagger, use GSAP. Otherwise CSS first.

Setup

// Always register plugins at the top level
import gsap from "gsap";
import { ScrollTrigger } from "gsap/ScrollTrigger";
import { SplitText } from "gsap/SplitText";

gsap.registerPlugin(ScrollTrigger, SplitText);

React: use useGSAP() from the @gsap/react package instead of useEffect + manual cleanup.

import { useGSAP } from "@gsap/react";

useGSAP(() => {
  gsap.to(".box", { x: 200 });
}, { scope: containerRef }); // auto-cleanup, auto-revert

Core Patterns

defaults{} to avoid repetition

const tl = gsap.timeline({
  defaults: { duration: 0.8, ease: "power2.out" },
});
tl.to(".a", { y: -20 })
  .to(".b", { y: -20 }, "<0.1")
  .to(".c", { y: -20 }, "<0.1");

fromTo for full control

gsap.fromTo(".card", { y: 40, opacity: 0 }, { y: 0, opacity: 1, stagger: 0.15 });

Stagger with distribution

gsap.to(".grid-item", {
  scale: 0,
  stagger: {
    each: 0.05,
    from: "center",   // "start" | "end" | "center" | "edges" | "random" | index
    grid: "auto",      // auto-detects the grid
    axis: "x",         // "x" | "y" | null (both)
  },
});

ScrollTrigger Patterns

Basic Pin + Scrub

gsap.to(".panel", {
  x: "-300%",
  ease: "none",
  scrollTrigger: {
    trigger: ".container",
    pin: true,
    scrub: 1,
    end: () => "+=" + document.querySelector(".container").scrollWidth,
  },
});

Batch for mass reveal

ScrollTrigger.batch(".card", {
  onEnter: (elements) => gsap.to(elements, { opacity: 1, y: 0, stagger: 0.1 }),
  start: "top 85%",
});

Horizontal scroll with containerAnimation

const scrollTween = gsap.to(".panels", {
  x: () => -(document.querySelector(".panels").scrollWidth - window.innerWidth),
  ease: "none",
  scrollTrigger: { trigger: ".wrapper", pin: true, scrub: 1 },
});

// Animate elements INSIDE the horizontal scroll
gsap.to(".panel-content", {
  scale: 1.2,
  scrollTrigger: {
    trigger: ".panel-content",
    containerAnimation: scrollTween, // linked to horizontal scroll
    start: "left center",
    end: "right center",
    scrub: true,
  },
});

DO NOT — Critical mistakes

1. Ease on containerAnimation

// BAD — ease breaks the scroll mapping
scrollTrigger: { containerAnimation: scrollTween, scrub: 1, ease: "power2.out" }

// GOOD — always ease: "none" on the parent tween
const scrollTween = gsap.to(".panels", { x: ..., ease: "none", scrollTrigger: { scrub: 1 } });

2. ScrollTrigger on a child tween in a timeline

// BAD — ScrollTrigger ignores child tweens of a timeline that has its own ScrollTrigger
const tl = gsap.timeline({ scrollTrigger: { trigger: ".section" } });
tl.to(".box", { x: 100, scrollTrigger: { trigger: ".box" } }); // IGNORE

// GOOD — one ScrollTrigger per timeline OR standalone tweens
gsap.to(".box", { x: 100, scrollTrigger: { trigger: ".box" } }); // tween standalone

3. setState in onUpdate

// BAD — setState 60x/s = re-render hell
scrollTrigger: { onUpdate: (self) => setProgress(self.progress) }

// GOOD — mutate a ref or DOM element directly
const progressRef = useRef(0);
scrollTrigger: { onUpdate: (self) => { progressRef.current = self.progress; } }
// Or better: gsap.quickSetter to mutate the DOM without React

4. immediateRender on from() in a timeline

// BAD — from() has immediateRender: true by default, breaks sequencing
tl.to(".box", { x: 100 });
tl.from(".box", { y: 50 }); // visually jumps to the start

// GOOD — disable immediateRender when from() follows another tween
tl.to(".box", { x: 100 });
tl.from(".box", { y: 50, immediateRender: false });

5. Animating non-transform properties

// BAD — width/height/top/left trigger layout reflow
gsap.to(".box", { width: 200, height: 200 });

// GOOD — use transforms (GPU-accelerated, composited)
gsap.to(".box", { scaleX: 1.5, scaleY: 1.5 });
// If actual size needed: use Flip plugin for layout transition

Refs

• references/core.md — Complete gsap.to/from/fromTo/set API, options
• references/timeline.md — Timeline, position parameter, nesting
• references/scrolltrigger.md — Full ScrollTrigger reference
• references/plugins.md — SplitText, Flip, MorphSVG, DrawSVG, MotionPath, Observer