50 checks in Core Web Vitals & Performance. Automated Its subsection has a live automated checker in the engine.
| ID | Check | Passes when |
|---|---|---|
| 4.1.01 | Extract field CWV metrics (LCP, CLS, INP) | Data present |
| 4.1.02 | Extract lab CWV metrics (Lighthouse scores) | Data present |
| 4.1.03 | Validate LCP < 2.5s (field) | Pass |
| 4.1.04 | Validate LCP element type (image, block) | Correct |
| 4.1.05 | Validate LCP is not a video thumbnail unless intended | Correct choice |
| 4.1.06 | Validate LCP served in next-gen format | WEBP/AVIF |
| 4.1.07 | Validate preloading of LCP image | <link rel="preload"> |
| 4.1.08 | Validate LCP image not delayed by JS | Not delayed |
| 4.1.09 | Validate LCP optimization triggers early (top of HTML) | Early |
| 4.1.10 | Validate INP < 200ms | Good responsiveness |
| 4.1.11 | Validate blocking event handlers reduced | Minimal block |
| 4.1.12 | Validate third-party JS does not increase INP | Minimal impact |
| 4.1.13 | Validate CLS < 0.1 | Stable layout |
| 4.1.14 | Identify unstable images without set width/height | Fixed dimensions |
| 4.1.15 | Identify ads shifting layout | Stabilized |
| 4.1.16 | Validate fonts loaded with font-display: swap | Yes |
| 4.1.17 | Detect flash of invisible text (FOIT) | None |
| 4.1.18 | Detect flash of unstyled content (FOUT) | Minimal |
| 4.1.19 | Validate first-contentful paint (FCP) < 1.8s | Fast |
| 4.1.20 | Validate time to first byte (TTFB) < 200ms | Optimal |
| 4.1.21 | Validate total blocking time (TBT) < 200ms | Good interaction |
| 4.1.22 | Validate main-thread blocking < 250ms | Good |
| 4.1.23 | Validate hydration time for JS frameworks | Fast |
| 4.1.24 | Validate minimized render-delay scripts | Yes |
| 4.1.25 | Validate usage of async/defer on scripts | Best practice |
| 4.1.26 | Validate unused JS < 30% | Low waste |
| 4.1.27 | Validate unused CSS < 30% | Low waste |
| 4.1.28 | Validate critical CSS extracted | Yes |
| 4.1.29 | Validate CSS does not block rendering | Non-blocking |
| 4.1.30 | Validate <style> injected early for above-the-fold | Yes |
| 4.1.31 | Validate server caching enabled | Strong caching |
| 4.1.32 | Validate CDN caching present | Present |
| 4.1.33 | Validate browser caching headers set | Good caching |
| 4.1.34 | Validate compression enabled (GZIP/Brotli) | Yes |
| 4.1.35 | Validate HTML minified | Yes |
| 4.1.36 | Validate JS bundles minified | Yes |
| 4.1.37 | Validate CSS minified | Yes |
| 4.1.38 | Validate HTTP/2 or HTTP/3 usage | Enabled |
| 4.1.39 | Validate preconnect for fonts & APIs | Present |
| 4.1.40 | Validate DNS-prefetch for third parties | Present |
| 4.1.41 | Validate no long-running tasks (>200ms) | Minimal |
| 4.1.42 | Validate minimal layout thrashing | Low |
| 4.1.43 | Validate low JS heap usage | Low |
| 4.1.44 | Detect memory leaks | None |
| 4.1.45 | Validate smooth scroll performance | Stable |
| 4.1.46 | Validate responsive images not delaying TTI | Optimized |
| 4.1.47 | Validate LCP element loaded in <2 resource hops | Optimized |
| 4.1.48 | Validate CLS stabilizers (aspect-ratio, width/height) | Present |
| 4.1.49 | Validate INP not inflated by JS listeners | Minimal impact |
| 4.1.50 | Compute Core Web Vitals composite score | >= 90% |
4.2 JavaScript Optimization & Bundling Suite →
A Deep Audit scores every check here that applies to your page, then an AI pass of up to 150 checks. Included on Pro and Ultra, or $9 for one audit.
See plansMachine-readable: catalog totals and the full catalog as JSON (IDs, section, weight, status).