ui-optimize

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name: ui-optimize description: Diagnose and fix UI performance: loading, rendering, animations

UI Optimize

/ui-optimize [target] - Diagnose and fix UI performance: loading speed, rendering, animations, images, bundle size.

Flow

1. Measure current state: Core Web Vitals (LCP, FID/INP, CLS), load time, bundle size, runtime perf
2. Identify bottlenecks: slowest part → root cause → severity → affected users
3. Optimize systematically by biggest impact first
4. Verify: measure before/after, test on real devices and slow connections

Optimization Areas

Loading Performance

• Images: WebP/AVIF, proper sizing, lazy loading, responsive srcset, CDN
• JS Bundle: code splitting, tree shaking, remove unused deps, dynamic imports
• CSS: remove unused, critical CSS inline, minimize
• Fonts: font-display: swap, subset, preload, limit weights
• Strategy: async/defer, preload, prefetch, service worker

Rendering Performance

• Avoid layout thrashing (batch reads then writes)
• CSS contain for independent regions
• content-visibility: auto for long lists
• Virtual scrolling for large lists
• Minimize DOM depth and size

Animation Performance

• GPU-accelerated only: transform and opacity
• Never animate layout properties (width, height, top, left)
• will-change sparingly for known expensive ops
• requestAnimationFrame for JS animations
• Target 16ms per frame (60fps)

Core Web Vitals

• LCP < 2.5s: optimize hero images, inline critical CSS, preload key resources, CDN, SSR
• INP < 200ms: break up long tasks, defer non-critical JS, web workers for heavy computation
• CLS < 0.1: set image dimensions, aspect-ratio, reserve space for dynamic content

Network

• Reduce request count (combine, SVG sprites, inline critical)
• Optimize APIs (pagination, GraphQL, compression, caching)
• Adaptive loading for slow connections
• Optimistic UI updates

NEVER

• Optimize without measuring
• Sacrifice accessibility for performance
• Break functionality while optimizing
• Use will-change everywhere
• Lazy load above-fold content
• Forget mobile (slower devices, slower connections)