bjornmelin/gsap-performance

GSAP Performance

When to Use This Skill

Apply when optimizing GSAP animations for smooth 60fps, reducing layout/paint cost, or when the user asks about performance, jank, or best practices for fast animations.

Related skills: Build animations with gsap-core (transforms, autoAlpha) and gsap-timeline; for ScrollTrigger performance see gsap-scrolltrigger.

Prefer Transform and Opacity

Animating transform (x, y, scaleX, scaleY, rotation, rotationX, rotationY, skewX, skewY) and opacity keeps work on the compositor and avoids layout and most paint. Avoid animating layout-heavy properties when a transform can achieve the same effect.

• ✅ Prefer: x, y, scale, rotation, opacity.
• ❌ Avoid when possible: width, height, top, left, margin, padding (they trigger layout and can cause jank).

GSAP’s x and y use transforms (translate) by default; use them instead of left/top for movement.

will-change

Use will-change in CSS on elements that will animate. It hints the browser to promote the layer.

will-change: transform;

Batch Reads and Writes

GSAP batches updates internally. When mixing GSAP with direct DOM reads/writes or layout-dependent code, avoid interleaving reads and writes in a way that causes repeated layout thrashing. Prefer doing all reads first, then all writes (or let GSAP handle the writes in one go).

Many Elements (Stagger, Lists)

• Use stagger instead of many separate tweens with manual delays when the animation is the same; it’s more efficient.
• For long lists, consider virtualization or animating only visible items; avoid creating hundreds of simultaneous tweens if it causes jank.
• Reuse timelines where possible; avoid creating new timelines every frame.

Frequently updated properties (e.g. mouse followers)

Prefer gsap.quickTo() for properties that are updated often (e.g. mouse-follower x/y). It reuses a single tween instead of creating new tweens on each update.

let xTo = gsap.quickTo("#id", "x", { duration: 0.4, ease: "power3" }),
    yTo = gsap.quickTo("#id", "y", { duration: 0.4, ease: "power3" });

document.querySelector("#container").addEventListener("mousemove", (e) => {
  xTo(e.pageX);
  yTo(e.pageY);
});

ScrollTrigger and Performance

• pin: true promotes the pinned element; pin only what’s needed.
• scrub with a small value (e.g. scrub: 1) can reduce work during scroll; test on low-end devices.
• Call ScrollTrigger.refresh() only when layout actually changes (e.g. after content load), not on every resize; debounce when possible.

Reduce Simultaneous Work

• Pause or kill off-screen or inactive animations when they’re not visible (e.g. when the user navigates away).
• Avoid animating huge numbers of properties on many elements at once; simplify or sequence if needed.

Best practices

• ✅ Animate transform and opacity; use will-change in CSS only on elements that animate.
• ✅ Use stagger instead of many separate tweens with manual delays when the animation is the same.
• ✅ Use gsap.quickTo() for frequently updated properties (e.g. mouse followers).
• ✅ Clean up or kill off-screen animations; call ScrollTrigger.refresh() when layout changes, debounced when possible.

Do Not

• ❌ Animate width/ height/ top/ left for movement when x/ y/ scale can achieve the same look.
• ❌ Set will-change or force3D on every element “just in case”; use for elements that are actually animating.
• ❌ Create hundreds of overlapping tweens or ScrollTriggers without testing on low-end devices.
• ❌ Ignore cleanup; stray tweens and ScrollTriggers keep running and can hurt performance and correctness.

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Codex Web Motion Overlay

The upstream GreenSock official skill content above is the primary GSAP guidance. This local overlay adds Codex-specific progressive-disclosure resources, static audit scripts, evals, and portable source metadata. Keep GSAP API behavior aligned with GreenSock's official skill and docs; use this overlay for validation, local boundaries, and report shape.

Local Boundaries

• Use web-three-r3f or typegpu for GPU/canvas rendering performance.
• Use web-css-animations for CSS-only transition audits.
• Use gsap-scrolltrigger for scroll scene semantics.

Local Workflow

1. Find hot paths and animated properties.
2. Classify layout, paint, composite, and JavaScript costs.
3. Run audit scan and inspect high-confidence findings.
4. Recommend transform/opacity, batching, throttling, or engine changes only with evidence.

Local Gotchas

• will-change is a scoped hint, not a global optimization.
• ScrollTrigger refresh calls after layout changes need ordering, not random timeouts.
• Infinite tweens need reduced-motion and cleanup behavior.

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Bundled Resources

• references/official-source.md - Official GreenSock performance skill source. Use this to verify upstream performance guidance.
• references/property-cost-matrix.md - Property cost and rendering matrix. Use this when classifying transform, opacity, layout, paint, filter, shadow, and text animation risk.
• references/scroll-performance.md - ScrollTrigger and scroll workload review. Use this for pinned scenes, scrubbed timelines, refresh timing, and scroll callback costs.
• references/profiling-playbook.md - GSAP profiling and evidence playbook. Read when a GSAP issue is described as jank, dropped frames, layout thrash, or slow scroll.
• references/layer-budget-and-will-change.md - Layer budget and will-change discipline. Read before adding transform hacks, force3D, will-change, or GPU promotion advice.
• references/index.md - Complete reference inventory and routing summary.
• references/source-ledger.md - Portable source list and copy policy.
• references/provenance.json - Machine-readable provenance and local-resource metadata.
• scripts/audit.mjs - Self-contained Codex audit CLI with domain-specific GSAP rules.
• assets/templates/gsap-performance-audit-report.md - GSAP audit response template.
• assets/templates/gsap-performance-review-checklist.md - GSAP manual review checklist.
• assets/examples/gsap-performance-starter.md - Minimal starter fixture/example.
• evals/trigger-queries.json - Trigger/near-miss eval set.
• evals/evals.json - Task-quality evals with assertions.

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Audit CLI

node scripts/audit.mjs doctor --root . --format json
node scripts/audit.mjs scan --root . --format markdown
node scripts/audit.mjs scan --root . --format json --output gsap-performance-audit.json

Treat script findings as leads. Verify every finding against current code before changing behavior or reporting it as valid.