Gsap Timeline Agent Skill

GSAP Timeline

> Curated from GreenSock's official GSAP skills: https://github.com/greensock/gsap-skills

When to Use This Skill

Apply when building multi-step animations, coordinating several tweens in sequence or parallel, or when the user asks about timelines, sequencing, or keyframe-style animation in GSAP.

Related skills: For single tweens and eases use gsap-core; for scroll-driven timelines use gsap-scrolltrigger; for React use gsap-react.

Creating a Timeline

const tl = gsap.timeline();
tl.to(".a", { x: 100, duration: 1 })
  .to(".b", { y: 50, duration: 0.5 })
  .to(".c", { opacity: 0, duration: 0.3 });

By default, tweens are appended one after another. Use the position parameter to place tweens at specific times or relative to other tweens.

Position Parameter

Third argument (or position property in vars) controls placement:

• Absolute: 1 — start at 1 second.
• Relative (default): "+=0.5" — 0.5s after end; "-=0.2" — 0.2s before end.
• Label: "labelName" — at that label; "labelName+=0.3" — 0.3s after label.
• Placement: "<" — start when recently-added animation starts; ">" — start when recently-added animation ends (default); "<0.2" — 0.2s after recently-added animation start.

Examples:

tl.to(".a", { x: 100 }, 0);           // at 0
tl.to(".b", { y: 50 }, "+=0.5");      // 0.5s after last end
tl.to(".c", { opacity: 0 }, "<");     // same start as previous
tl.to(".d", { scale: 2 }, "<0.2");    // 0.2s after previous start

Timeline Defaults

Pass defaults into the timeline so all child tweens inherit:

const tl = gsap.timeline({ defaults: { duration: 0.5, ease: "power2.out" } });
tl.to(".a", { x: 100 }).to(".b", { y: 50 }); // both use 0.5s and power2.out

Timeline Options (constructor)

• paused: true — create paused; call .play() to start.
• repeat, yoyo — same as tweens; apply to whole timeline.
• onComplete, onStart, onUpdate — timeline-level callbacks.
• defaults — vars merged into every child tween.

Labels

Add and use labels for readable, maintainable sequencing:

tl.addLabel("intro", 0);
tl.to(".a", { x: 100 }, "intro");
tl.addLabel("outro", "+=0.5");
tl.to(".b", { opacity: 0 }, "outro");
tl.play("outro");  // start from "outro"
tl.tweenFromTo("intro", "outro"); // pauses the timeline and returns a new Tween that animates the timeline's playhead from intro to outro with no ease.

Nesting Timelines

Timelines can contain other timelines.

const master = gsap.timeline();
const child = gsap.timeline();
child.to(".a", { x: 100 }).to(".b", { y: 50 });
master.add(child, 0);
master.to(".c", { opacity: 0 }, "+=0.2");

Controlling Playback

• tl.play() / tl.pause()
• tl.reverse() / tl.progress(1) then tl.reverse()
• tl.restart() — from start.
• tl.time(2) — seek to 2 seconds.
• tl.progress(0.5) — seek to 50%.
• tl.kill() — kill timeline and (by default) its children.

Official GSAP Best practices

• ✅ Prefer timelines for sequencing
• ✅ Use the position parameter (third argument) to place tweens at specific times or relative to labels.
• ✅ Add labels with addLabel() for readable, maintainable sequencing.
• ✅ Pass defaults into the timeline constructor so child tweens inherit duration, ease, etc.
• ✅ Put ScrollTrigger on the timeline (or top-level tween), not on tweens inside a timeline.

Do Not

• ❌ Chain animations with delay when a timeline can sequence them; prefer gsap.timeline() and the position parameter for multi-step animation.
• ❌ Forget to pass defaults (e.g. defaults: { duration: 0.5, ease: "power2.out" }) when many child tweens share the same duration or ease.
• ❌ Forget that duration on the timeline constructor is not the same as tween duration; timeline “duration” is determined by its children.
• ❌ Nest animations that contain a ScrollTrigger; ScrollTriggers should only be on top-level Tweens/Timelines.