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

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