Emil Kowalski Animation Best Practices

Comprehensive animation guide for web interfaces based on Emil Kowalski's teachings, open-source libraries (Sonner, Vaul), and his animations.dev course. Contains 43 rules across 7 categories, prioritized by impact.

When to Apply

Reference these guidelines when:

• Adding animations to React components

• Choosing easing curves or timing values

• Implementing gesture-based interactions (swipe, drag)

• Building toast notifications or drawer components

• Optimizing animation performance

• Ensuring animation accessibility

Rule Categories by Priority

Priority Category Impact Prefix

1 Easing Selection CRITICAL ease-

2 Timing & Duration CRITICAL timing-

3 Property Selection HIGH props-

4 Transform Techniques HIGH transform-

5 Interaction Patterns MEDIUM-HIGH interact-

6 Strategic Animation MEDIUM strategy-

7 Accessibility & Polish MEDIUM polish-

Quick Reference

1. Easing Selection (CRITICAL)

• ease-out-default

• Use ease-out as your default easing

• ease-custom-curves

• Use custom cubic-bezier over built-in CSS

• ease-in-out-onscreen

• Use ease-in-out for on-screen movement

• ease-spring-natural

• Use spring animations for natural motion

• ease-ios-drawer

• Use iOS-style easing for drawer components

• ease-context-matters

• Match easing to animation context

2. Timing & Duration (CRITICAL)

• timing-300ms-max

• Keep UI animations under 300ms

• timing-faster-better

• Faster animations improve perceived performance

• timing-asymmetric

• Use asymmetric timing for press and release

• timing-tooltip-delay

• Delay initial tooltips, instant subsequent ones

• timing-drawer-500ms

• Use 500ms duration for drawer animations

3. Property Selection (HIGH)

• props-transform-opacity

• Animate only transform and opacity

• props-hardware-accelerated

• Use hardware-accelerated animations when main thread is busy

• props-will-change

• Use will-change to prevent 1px shift

• props-avoid-css-variables

• Avoid CSS variables for drag animations

• props-clip-path-performant

• Use clip-path for layout-free reveals

4. Transform Techniques (HIGH)

• transform-scale-097

• Scale buttons to 0.97 on press

• transform-never-scale-zero

• Never animate from scale(0)

• transform-percentage-translate

• Use percentage values for translateY

• transform-origin-aware

• Make animations origin-aware

• transform-scale-children

• Scale transforms affect children

• transform-3d-preserve

• Use preserve-3d for 3D transform effects

5. Interaction Patterns (MEDIUM-HIGH)

• interact-interruptible

• Make animations interruptible

• interact-momentum-dismiss

• Use momentum-based dismissal

• interact-damping

• Damp drag at boundaries

• interact-scroll-drag-conflict

• Resolve scroll and drag conflicts

• interact-snap-points

• Implement velocity-aware snap points

• interact-friction-upward

• Allow upward drag with friction

• interact-pointer-capture

• Use pointer capture for drag operations

6. Strategic Animation (MEDIUM)

• strategy-keyboard-no-animate

• Never animate keyboard-initiated actions

• strategy-frequency-matters

• Consider interaction frequency before animating

• strategy-purpose-required

• Every animation must have a purpose

• strategy-feedback-immediate

• Provide immediate feedback on all actions

• strategy-marketing-exception

• Marketing sites are the exception

7. Accessibility & Polish (MEDIUM)

• polish-reduced-motion

• Respect prefers-reduced-motion

• polish-opacity-fallback

• Use opacity as reduced motion fallback

• polish-framer-hook

• Use useReducedMotion hook in Framer Motion

• polish-dont-remove-all

• Don't remove all animation for reduced motion

• polish-blur-bridge

• Use blur to bridge animation states

• polish-clip-path-tabs

• Use clip-path for tab transitions

• polish-toast-stacking

• Implement toast stacking with scale and offset

• polish-scroll-reveal

• Trigger scroll animations at appropriate threshold

• polish-hover-gap-fill

• Fill gaps between hoverable elements

• polish-stagger-children

• Stagger child animations for orchestration

Key Values Reference

Value Usage

cubic-bezier(0.32, 0.72, 0, 1)

iOS-style drawer/sheet animation

scale(0.97)

Button press feedback

scale(0.95)

Minimum enter scale (never scale(0))

200ms ease-out

Standard UI transition

300ms

Maximum duration for UI animations

500ms

Drawer animation duration

0.11 px/ms

Velocity threshold for momentum dismiss

100px

Scroll-reveal viewport threshold

14px

Toast stack offset

Reference Files

Category Example References

Easing ease-context-matters, ease-ios-drawer

Timing timing-300ms-max, timing-drawer-500ms

Props & Transform props-transform-opacity, transform-scale-097

Interaction & Polish interact-interruptible, polish-reduced-motion