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 58 rules across 8 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
• Expressing any of the above with Tailwind CSS v4 utilities (see the tw- category)

Rule Categories by Priority

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-spring-config - Configure springs with duration and bounce
• 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
• transform-starting-style - Animate enter states with @starting-style

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
• interact-multitouch - Ignore extra touch points during drag
• interact-touch-hover - Gate hover animations behind a pointer media query

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
• strategy-cohesion - Match motion to the component's personality
• strategy-review-fresh-eyes - Review animations in slow motion and the next day

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 - Keep gentle 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

8. Tailwind v4 Utilities (MEDIUM)

Express the principles above with proper Tailwind CSS v4 utilities. Applies only to Tailwind v4 projects; the raw-CSS and Framer Motion rules above remain the source of truth.

• tw-ease-duration-defaults - Set ease-out and a sub-300ms duration explicitly
• tw-custom-easing-theme - Register custom easing curves as @theme tokens
• tw-press-scale - Use active:scale-[0.97] for button press feedback
• tw-asymmetric-timing - Split press and release timing with active:duration
• tw-starting-enter - Animate enter states with the starting: variant
• tw-reduced-motion - Gate movement behind motion-safe / motion-reduce
• tw-origin-aware - Set transform-origin with origin-* utilities
• tw-will-change - Scope will-change-transform to the active gesture

Key Values Reference

Duration by Element

Pick duration by how often the element is seen and how much it moves. Keep UI animations under 300ms.

Reference Files