45 checks in Core Web Vitals & Performance. Automated Its subsection has a live automated checker in the engine.
| ID | Check | Passes when |
|---|---|---|
| 4.2.01 | Extract total JS payload | < 200KB compressed |
| 4.2.02 | Extract uncompressed JS size | < 1MB |
| 4.2.03 | Validate JS bundles are split | Code-splitting enabled |
| 4.2.04 | Validate lazy-loading for non-critical components | Enabled |
| 4.2.05 | Validate tree-shaking effectiveness | No dead code |
| 4.2.06 | Validate module-level imports (no wildcard imports) | Optimized |
| 4.2.07 | Validate vendor bundle separation | Yes |
| 4.2.08 | Validate frameworks use production mode builds | Production mode |
| 4.2.09 | Identify unused JS ≥ 30% | Minimized |
| 4.2.10 | Validate number of <script> tags | Minimal critical scripts |
| 4.2.11 | Validate async/defer usage | Correct |
| 4.2.12 | Validate inline JS is minimized | Minimal inline JS |
| 4.2.13 | Validate JS doesn’t block rendering | Non-blocking |
| 4.2.14 | Validate hydration < 2s on mid-tier device | Good |
| 4.2.15 | Validate hydration chunks optimized | Balanced |
| 4.2.16 | Detect excessive client-side routing cost | Minimal |
| 4.2.17 | Validate use of Partial Hydration (Astro / Qwik / React Server Components where possible) | Modern hydration |
| 4.2.18 | Validate React Server Components usage (for React/Next) | Implemented |
| 4.2.19 | Validate minimal hydration for static UI | Correct hydration |
| 4.2.20 | Validate reduced JS for static sections | Low JS |
| 4.2.21 | Validate bundler (Vite/ESBuild/Turbopack) configured optimally | Optimized |
| 4.2.22 | Validate rollup chunks named logically | Clean structure |
| 4.2.23 | Validate code splitting for heavy dependencies | Done |
| 4.2.24 | Detect heavy dependencies (>50KB each) | Avoid or optimize |
| 4.2.25 | Validate removal of unused polyfills | Clean |
| 4.2.26 | Validate polyfill size < 20KB | Light |
| 4.2.27 | Validate JS compression (Brotli preferred) | Yes |
| 4.2.28 | Validate HTTP/2 multiplexing used | Yes |
| 4.2.29 | Validate JS execution time < 300ms | Fast |
| 4.2.30 | Detect long-running tasks > 200ms | None |
| 4.2.31 | Validate Web Workers usage where applicable | Optimized |
| 4.2.32 | Validate Service Worker not overloading main thread | Efficient |
| 4.2.33 | Validate prefetching for dynamic routes | Present |
| 4.2.34 | Validate Module Federation (micro-frontends) not bloating payload | Light |
| 4.2.35 | Validate global state libraries minimized (Redux/MobX/etc.) | Lightweight |
| 4.2.36 | Validate caching for JS assets at CDN | Present |
| 4.2.37 | Validate preconnects to JS CDNs | Present |
| 4.2.38 | Validate hot path JS functions optimized | Efficient |
| 4.2.39 | Detect excessive DOM manipulations | Minimal |
| 4.2.40 | Validate low event listener overhead | Minimal |
| 4.2.41 | Identify memory leaks from JS | None |
| 4.2.42 | Validate correct usage of requestIdleCallback | Yes |
| 4.2.43 | Validate correct usage of requestAnimationFrame | Yes |
| 4.2.44 | Validate JS doesn’t block user input | Responsive |
| 4.2.45 | Compute JS Optimization composite score | >= 90% |
← 4.1 Core Web Vitals Suite4.3 CSS Optimization & Render-Path Suite →
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