GSAP Easing

Easing functions control how animations progress over time. GSAP provides extensive built-in eases plus plugins for custom curves, elastic effects, and bounce animations.

Basic Eases

Power Eases

// Power0 - Linear (no easing)
gsap.to('.box', {
  x: 200,
  duration: 1,
  ease: 'none'  // Same as 'power0'
})

// Power1 - Default
gsap.to('.box', {
  x: 200,
  duration: 1,
  ease: 'power1.out'  // GSAP default
})

// Power2
gsap.to('.box', {
  x: 200,
  duration: 1,
  ease: 'power2.out'
})

// Power3
gsap.to('.box', {
  x: 200,
  duration: 1,
  ease: 'power3.out'
})

// Power4 - Strongest curve
gsap.to('.box', {
  x: 200,
  duration: 1,
  ease: 'power4.out'
})

Ease Modifiers

// In - Slow start, fast end
gsap.to('.box', {
  x: 200,
  duration: 1,
  ease: 'power2.in'
})

// Out - Fast start, slow end
gsap.to('.box', {
  x: 200,
  duration: 1,
  ease: 'power2.out'
})

// InOut - Slow both ends, fast middle
gsap.to('.box', {
  x: 200,
  duration: 1,
  ease: 'power2.inOut'
})

Back Ease

// Back.out - Overshoots target then settles
gsap.to('.box', {
  x: 200,
  duration: 1,
  ease: 'back.out(1.7)  // 1.7 is overshoot amount
})

// Back.in - Pulls back first
gsap.to('.box', {
  x: 200,
  duration: 1,
  ease: 'back.in(1.7)'
})

// Back.inOut - Both directions
gsap.to('.box', {
  x: 200,
  duration: 1,
  ease: 'back.inOut(1.7)'
})

Elastic Ease

// Elastic.out - Springy overshoot
gsap.to('.box', {
  x: 200,
  duration: 1,
  ease: 'elastic.out(1, 0.3)'
  // First param: amplitude (1 = no overshoot)
  // Second param: period (lower = more wiggles)
})

// Elastic.in - Elastic start
gsap.to('.box', {
  x: 200,
  duration: 1,
  ease: 'elastic.in(1, 0.3)'
})

// Elastic.inOut - Both directions
gsap.to('.box', {
  x: 200,
  duration: 1,
  ease: 'elastic.inOut(1, 0.3)'
})

Bounce Ease

// Bounce.out - Ball-like bounce at end
gsap.to('.box', {
  y: -200,
  duration: 1,
  ease: 'bounce.out'
})

// Bounce.in - Bounce at start
gsap.to('.box', {
  y: -200,
  duration: 1,
  ease: 'bounce.in'
})

// Bounce.inOut - Bounce both ends
gsap.to('.box', {
  y: -200,
  duration: 1,
  ease: 'bounce.inOut'
})

Expo Ease

// Expo.out - Very strong ease out
gsap.to('.box', {
  x: 200,
  duration: 1,
  ease: 'expo.out'
})

// Expo.in - Very strong ease in
gsap.to('.box', {
  x: 200,
  duration: 1,
  ease: 'expo.in'
})

// Expo.inOut - Both very strong
gsap.to('.box', {
  x: 200,
  duration: 1,
  ease: 'expo.inOut'
})

Circ and Sine

// Circ - Circular easing
gsap.to('.box', {
  x: 200,
  duration: 1,
  ease: 'circ.out'
})

// Sine - Gentle sine wave
gsap.to('.box', {
  x: 200,
  duration: 1,
  ease: 'sine.out'
})

Steps Ease

Basic Steps

// 5 discrete steps
gsap.to('.box', {
  x: 200,
  duration: 1,
  ease: 'steps(5)'
})

Steps with Direction

// Start at top of step
gsap.to('.box', {
  x: 200,
  duration: 1,
  ease: 'steps(5, start)'
})

// End at top of step
gsap.to('.box', {
  x: 200,
  duration: 1,
  ease: 'steps(5, end)'
})

// Both
gsap.to('.box', {
  x: 200,
  duration: 1,
  ease: 'steps(5, both)'
})

Steps for Sprite Animation

gsap.to('.sprite', {
  backgroundPosition: `-${frameWidth * 7}px 0`,
  duration: 0.8,
  ease: 'steps(7)',  // 7 frames
  repeat: -1
})

EasePack Plugin

SlowMo

npm install gsap

import { EasePack } from 'gsap/EasePack'
gsap.registerPlugin(EasePack)

// SlowMo - Decelerates, holds, accelerates
gsap.to('.box', {
  x: 200,
  duration: 2,
  ease: 'slow(0.7, 0.7, false)'
  // First: ease portion
  // Second: hold portion
  // Third: ease out portion (true/false)
})

RoughEase

// RoughEase - Jagged, organic feel
gsap.to('.box', {
  x: 200,
  duration: 2,
  ease: 'rough({
    template: 'power1.out',
    strength: 1,
    points: 20,
    taper: 'both',
    randomize: true,
    clamp: false
  })
})

// Pre-configured rough eases
gsap.to('.box', {
  x: 200,
  duration: 2,
  ease: 'rough.ease'  // Simplified
})

ExpoScale

// ExpoScale - For scaling animations
gsap.to('.box', {
  scale: 5,
  duration: 2,
  ease: 'expoScale(0.5, 3, 'power2.inOut)'
  // From scale, to scale, ease function
})

CustomEase (formerly members-only; now included)

Create Custom Ease

npm install gsap

import { CustomEase } from 'gsap/CustomEase'
gsap.registerPlugin(CustomEase)

// Create from SVG path
CustomEase.create('myEase', 'M0,0 C0.5,0 0.5,1 1,1')

gsap.to('.box', {
  x: 200,
  duration: 1,
  ease: 'myEase'
})

Create from Points

CustomEase.create('myEase', [
  { x: 0, y: 0 },
  { x: 0.3, y: 0.2, controlPoint: { x: 0.15, y: 0 } },
  { x: 0.7, y: 0.8, controlPoint: { x: 0.85, y: 1 } },
  { x: 1, y: 1 }
])

Get SVG Path

// Visual method - get path from UI
CustomEase.create('visualEase', 'M0,100 C50,0 100,100 100,100')

CustomWiggle (formerly members-only; now included)

import { CustomWiggle } from 'gsap/CustomWiggle'
gsap.registerPlugin(CustomWiggle)

// Create wiggle ease
CustomWiggle.create('myWiggle', {
  wiggles: 2,
  amplitude: 1
})

gsap.to('.box', {
  x: 200,
  rotation: 20,
  duration: 2,
  ease: 'myWiggle'
})

CustomBounce (formerly members-only; now included)

import { CustomBounce } from 'gsap/CustomBounce'
gsap.registerPlugin(CustomBounce)

// Create custom bounce
CustomBounce.create('myBounce', {
  squash: 2,
  bounce: 5
})

gsap.to('.ball', {
  y: -200,
  duration: 1,
  ease: 'myBounce'
})

Ease Selection Guide

By Use Case

Effect	Recommended Ease
Default UI	power2.out
Entrance	back.out(1.7) or power3.out
Exit	power2.in
Attention	elastic.out(1, 0.3)
Playful	bounce.out
Smooth	sine.inOut
Punchy	power4.out
Organic	rough.ease
Subtle	power1.inOut
Natural	expo.inOut
Step	steps(5)

By Property

Property	Recommended Ease
Position (x,y)	power2.out, back.out
Scale	back.out(1.7), elastic.out
Rotation	elastic.out, back.out
Opacity	power2.out, sine.out
Color	power1.out
Filter	power1.out

Timeline Ease Control

Per-Tween Ease

const tl = gsap.timeline()

tl.to('.box1', {
    x: 100,
    duration: 1,
    ease: 'power2.out'  // Individual ease
  })
  .to('.box2', {
    x: 100,
    duration: 1,
    ease: 'back.out'  // Different ease
  })

Timeline Defaults

const tl = gsap.timeline({
  defaults: {
    ease: 'power2.out',  // Default for all tweens
    duration: 1
  }
})

tl.to('.box1', { x: 100 })  // Uses default ease
  .to('.box2', {
    x: 100,
    ease: 'back.out'  // Overrides default
  })

Ease Each

// Keyframes with per-keyframe ease
gsap.to('.box', {
  keyframes: [
    { x: 100, ease: 'power2.out' },
    { y: 100, ease: 'back.out' },
    { x: 0, y: 0, ease: 'power2.out' }
  ],
  easeEach: 'power1.out'  // If individual ease not specified
})

Ease Testing

Visual Comparison

const eases = [
  'none',
  'power1.out',
  'power2.out',
  'power3.out',
  'power4.out',
  'back.out(1.7)',
  'elastic.out(1, 0.3)',
  'bounce.out'
]

eases.forEach((ease, i) => {
  gsap.to(`.box-${i}`, {
    x: 200,
    duration: 1,
    ease: ease,
    delay: i * 1.2
  })
})

Ease Visualization

function visualizeEase(easeName) {
  const path = []
  for (let i = 0; i <= 100; i++) {
    const progress = i / 100
    const easedValue = gsap.parseEase(easeName)(progress)
    path.push({ x: progress * 100, y: (1 - easedValue) * 100 })
  }

  // Draw SVG path
  const d = 'M' + path.map(p => `${p.x},${p.y}`).join(' L')
  console.log(d)
}

visualizeEase('power2.out')

Performance Considerations

Use Power Eases

// ❌ Complex eases on many elements
gsap.to('.many-boxes', {
  x: 200,
  ease: 'elastic.out(1, 0.3)',  // Computationally expensive
  stagger: 0.05
})

// ✅ Simpler eases for performance
gsap.to('.many-boxes', {
  x: 200,
  ease: 'power2.out',  // Faster
  stagger: 0.05
})

Ease Caching

// Parse and cache ease
const myEase = gsap.parseEase('power2.out')

// Use cached ease
gsap.to('.box', {
  x: 200,
  ease: myEase
})

Common Patterns

Elastic Entrance

gsap.from('.modal', {
  scale: 0,
  opacity: 0,
  duration: 0.8,
  ease: 'back.out(1.7)'
})

Bouncy Button

const btn = document.querySelector('.button')

btn.addEventListener('mouseenter', () => {
  gsap.to(btn, {
    scale: 1.1,
    duration: 0.3,
    ease: 'elastic.out(1, 0.5)'
  })
})

btn.addEventListener('mouseleave', () => {
  gsap.to(btn, {
    scale: 1,
    duration: 0.3,
    ease: 'power2.out'
  })
})

Smooth Scroll

gsap.to(window, {
  scrollTo: { y: target },
  duration: 1,
  ease: 'power2.inOut'
})

Natural Motion

gsap.to('.ball', {
  y: 500,
  duration: 1.5,
  ease: 'bounce.out'
})

Common Mistakes

1. Wrong Ease for Context

// ❌ Elastic for subtle hover
gsap.to('.link', {
  color: '#ff0000',
  ease: 'elastic.out(1, 0.3)',
  duration: 0.3
})

// ✅ Use appropriate ease
gsap.to('.link', {
  color: '#ff0000',
  ease: 'power2.out',
  duration: 0.3
})

2. Using Wrong Ease Direction

// ❌ Using in for entrance
gsap.from('.box', {
  opacity: 0,
  ease: 'power2.in'  // Wrong direction!
})

// ✅ Use out for entrance
gsap.from('.box', {
  opacity: 0,
  ease: 'power2.out'
})

3. Overpowering Overshoot

// ❌ Too much overshoot
gsap.to('.box', {
  x: 200,
  ease: 'back.out(5)'  // Too aggressive!
})

// ✅ Reasonable overshoot
gsap.to('.box', {
  x: 200,
  ease: 'back.out(1.7)'  // Sweet spot
})

Best Practices

1. Match ease to use case - UI, playful, natural
2. Consider property type - Different properties benefit from different eases
3. Test different eases - Try multiple options
4. Use power eases for performance - Simpler = faster
5. Reserve complex eases for attention - Don't overuse elastic/bounce
6. Set timeline defaults - Consistent feel across animations
7. Visualize eases - Understand curve behavior
8. Consider user experience - Don't make users wait

Quick Reference

Ease	Description
none	Linear (no easing)
power1.out	Default GSAP ease
power2.out	Standard UI ease
back.out(1.7)	Overshoots target
elastic.out(1, 0.3)	Springy oscillation
bounce.out	Ball-like bounce
expo.out	Very strong ease
sine.out	Gentle sine wave
steps(5)	Discrete steps
circ.out	Circular easing
rough.ease	Organic, jagged
slow(0.7)	Decelerate-hold-accelerate