dot-skills — Airbnb iOS SwiftUI Animations Best Practices

Opinionated, strict animation craft guide for SwiftUI iOS 26 / Swift 6.2 apps. Contains 50 rules across 8 categories, prioritized by impact. Derived from Airbnb Engineering motion patterns, Apple WWDC sessions, and Apple Human Interface Guidelines. Mandates @Equatable on every animated view, motion tokens for all spring/timing values, and design system tokens for layout.

Mandated Architecture Alignment

This skill is designed to work alongside

swift-ui-architect

and

ios-design-system

. All code examples follow the same non-negotiable constraints:

```
@Equatable
```
macro on every view (Airbnb measured 15% scroll hitch reduction)
```
@Observable
```
for complex animation state that involves business logic triggers
```
@State
```
for view-owned animation state (toggle booleans, drag offsets)
Design system tokens:
```
Spacing.xs/sm/md/lg
```
,
```
Radius.sm/md/lg
```
— zero hardcoded layout numbers
Motion tokens:
```
Motion.standard/responsive/playful
```
— zero scattered spring literals
Semantic colors:
```
.backgroundSurface
```
,
```
.accentPrimary
```
— no raw Color literals in views
Feature animations remain presentation-only; data/network concerns stay in Data package

Scope & Relationship to Sibling Skills

This skill is the motion layer — it teaches how to BUILD fluid, performant animations. When loaded alongside sibling skills:

Sibling Skill	Its Focus	This Skill's Focus
`swift-ui-architect`	Architecture (modular MVVM-C, route shells, protocol boundaries)	Animation architecture (motion tokens, spring selection, orchestration)
`ios-design-system`	Design system infrastructure (tokens, styles, governance)	Motion tokens and animated component patterns
`ios-hig`	HIG compliance patterns	Motion-specific HIG (reduce motion, spatial continuity)

Out of scope: Designer-authored vector animations (use Lottie for After Effects exports). Complex UIKit transition controllers (see Airbnb's declarative transition framework). This skill covers programmatic SwiftUI animations only.

Clinic Architecture Contract (iOS 26 / Swift 6.2)

All guidance in this skill assumes the clinic modular MVVM-C architecture:

Feature modules import
```
Domain
```
+
```
DesignSystem
```
only (never
```
Data
```
, never sibling features)
App target is the convergence point and owns
```
DependencyContainer
```
, concrete coordinators, and Route Shell wiring
```
Domain
```
stays pure Swift and defines models plus repository,
```
*Coordinating
```
,
```
ErrorRouting
```
, and
```
AppError
```
contracts
```
Data
```
owns SwiftData/network/sync/retry/background I/O and implements Domain protocols
Read/write flow defaults to stale-while-revalidate reads and optimistic queued writes
ViewModels call repository protocols directly (no default use-case/interactor layer)

When to Apply

Reference these guidelines when:

Adding animations to SwiftUI views or transitions
Building gesture-driven interactions (drag, swipe, pan)
Connecting views with spatial transitions (expand/collapse, navigation morphs)
Designing micro-interactions (button press, toggle, loading states)
Making content changes feel physical (number rolls, symbol replacements)
Choreographing multi-element animation sequences (KeyframeAnimator, PhaseAnimator)
Defining motion tokens for a design system
Reviewing animation code for performance, accessibility, and architecture compliance

Rule Categories by Priority


spring-
feel-
gesture-
spatial-
micro-
orch-
craft-
content-

Priority	Category	Impact	Prefix	Rules
1	Spring Physics	CRITICAL	`spring-`	8
2	Timing & Feel	CRITICAL	`feel-`	6
3	Gesture Continuity	HIGH	`gesture-`	7
4	Spatial Transitions	HIGH	`spatial-`	6
5	Micro-interactions	HIGH	`micro-`	6
6	Orchestration	HIGH	`orch-`	5
7	Craft & Polish	HIGH	`craft-`	5
8	Content Motion	MEDIUM-HIGH	`content-`	5

Quick Reference

1. Spring Physics (CRITICAL)

```
spring-motion-tokens
```
— Define motion tokens as a caseless enum for all spring presets
```
spring-smooth-default
```
— Default to .smooth spring for all UI transitions
```
spring-snappy-responsive
```
— Use .snappy spring for responsive interactions
```
spring-bouncy-celebration
```
— Use .bouncy spring for playful and celebratory moments
```
spring-custom-parameters
```
— Tune custom springs with response and dampingFraction
```
spring-velocity-preservation
```
— Springs preserve velocity on interruption
```
spring-never-linear
```
— Never use linear or easeInOut for interactive UI
```
spring-completion-chaining
```
— Use withAnimation completion for chained sequences

2. Timing & Feel (CRITICAL)

```
feel-250ms-max
```
— Keep UI animations under 250ms
```
feel-faster-better
```
— Faster animations almost always feel better
```
feel-asymmetric-enter-exit
```
— Use asymmetric timing for enter and exit
```
feel-distance-proportional
```
— Match duration to distance traveled
```
feel-haptic-sync
```
— Sync haptic feedback to visual animation keyframes
```
feel-stagger-timing
```
— Stagger reveals at 30-50ms intervals

3. Gesture Continuity (HIGH)

```
gesture-rubber-band
```
— Rubber band at drag boundaries
```
gesture-momentum-dismiss
```
— Dismiss on velocity OR distance threshold
```
gesture-snap-points
```
— Use velocity-aware snap points
```
gesture-interruptible
```
— Make all gesture animations interruptible
```
gesture-scroll-drag-conflict
```
— Resolve scroll and drag gesture conflicts
```
gesture-state-transient
```
— Use GestureState for transient drag state
```
gesture-projected-landing
```
— Project gesture velocity for natural landing position

4. Spatial Transitions (HIGH)

```
spatial-matched-geometry
```
— Use matchedGeometryEffect for expand/collapse morphs
```
spatial-zoom-navigation
```
— Use zoom navigation transition for collection detail (iOS 18)
```
spatial-transition-origin
```
— Anchor transitions to their trigger location
```
spatial-hero-shared-element
```
— Share multiple element IDs for rich hero animations
```
spatial-sheet-morph
```
— Use matchedGeometryEffect for sheet presentations
```
spatial-tab-continuity
```
— Maintain spatial direction in tab transitions

5. Micro-interactions (HIGH)

```
micro-button-press-scale
```
— Scale buttons to 0.97 on press for tactile feedback
```
micro-haptic-pairing
```
— Pair every visual state change with haptic feedback
```
micro-symbol-effect
```
— Use symbolEffect for SF Symbol animations
```
micro-toggle-bounce
```
— Add bounce to toggle state changes
```
micro-long-press-fill
```
— Animate progressive fill for long press actions
```
micro-loading-phase
```
— Use repeating spring for organic loading states

6. Orchestration (HIGH)

```
orch-phase-animator
```
— Use PhaseAnimator for multi-step sequences
```
orch-keyframe-animator
```
— Use KeyframeAnimator for timeline-precise motion
```
orch-stagger-children
```
— Stagger child elements for orchestrated reveals
```
orch-coordinated-entrance
```
— Coordinate multi-element entrances with shared trigger
```
orch-timeline-view
```
— Use TimelineView for continuous repeating animations

7. Craft & Polish (HIGH)

```
craft-reduce-motion
```
— Respect accessibilityReduceMotion with crossfade fallback
```
craft-blur-bridge
```
— Use blur to bridge imperfect transition states
```
craft-drawing-group
```
— Use drawingGroup() for Metal-backed complex animations
```
craft-geometry-group
```
— Use geometryGroup() to isolate layout animation propagation
```
craft-transaction-debug
```
— Use Transaction to debug and override animation behavior

8. Content Motion (MEDIUM-HIGH)

```
content-numeric-text
```
— Use contentTransition(.numericText) for number changes
```
content-scroll-transition
```
— Use scrollTransition for scroll-position effects
```
content-visual-effect
```
— Use visualEffect for position-aware animations
```
content-symbol-replace
```
— Animate symbol replacement with contentTransition
```
content-text-renderer
```
— Use Text Renderer for character-level animation (iOS 18)

How to Use

Read individual reference files for detailed explanations with incorrect/correct code examples:

Section definitions — Category structure and impact levels
Rule template — Template for adding new rules

Reference Files

File	Description
references/_sections.md	Category definitions and ordering
assets/templates/_template.md	Template for new rules
metadata.json	Version and reference information

ios-animations

NPX Install

Tags

SKILL.md Content