GreenSock's official agent skills for GSAP. The timeline skill teaches sequencing with the position parameter, labels, defaults and nesting, so agent-written web motion is choreographed rather than chained.
By GreenSock @greensock Mar 4, 2026
## 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:
```javascript
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
```
[…]
## 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. From GreenSock's repo, under the MIT license.
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