40 checks in Core Web Vitals & Performance. Automated Its subsection has a live automated checker in the engine.
| ID | Check | Passes when |
|---|---|---|
| 4.5.01 | Identify Largest Contentful Paint (LCP) image | Correctly detected |
| 4.5.02 | Validate LCP image loads < 2.5s | Pass |
| 4.5.03 | Validate LCP image preload tag exists | <link rel="preload"> present |
| 4.5.04 | Validate LCP image size matches display size | Within 10% |
| 4.5.05 | Validate responsive image usage (srcset) | Full coverage |
| 4.5.06 | Validate sizes attribute present | Correct |
| 4.5.07 | Validate modern formats (WEBP/AVIF) used | Yes |
| 4.5.08 | Validate fallback images exist | Present |
| 4.5.09 | Validate compression ratio optimal | 60–85% |
| 4.5.10 | Validate images served from CDN | Yes |
| 4.5.11 | Validate correct caching headers | Long TTL |
| 4.5.12 | Validate lazy-loading for below-fold images | Yes |
| 4.5.13 | Validate no lazy-loading on LCP image | Correct |
| 4.5.14 | Identify oversized images (filesize >> displayed) | None |
| 4.5.15 | Validate aspect-ratio attributes included | Yes |
| 4.5.16 | Validate width/height attributes prevent CLS | Present |
| 4.5.17 | Validate images do not block rendering | Async/non-blocking |
| 4.5.18 | Detect duplicate image downloads | None |
| 4.5.19 | Validate Next.js or Supabase auto-optimization | Enabled |
| 4.5.20 | Validate Cloudflare Polish, Image Resizing, or similar | Enabled |
| 4.5.21 | Validate caching works across mobile/desktop variants | Yes |
| 4.5.22 | Validate ETag/Last-Modified headers | Present |
| 4.5.23 | Validate WebP/AVIF browser compatibility fallback | Correct |
| 4.5.24 | Validate large hero images not too heavy (>300KB) | Optimized |
| 4.5.25 | Validate fast load on mid-tier mobile | <1s for hero |
| 4.5.26 | Validate correct image CDN routing | Low latency |
| 4.5.27 | Identify incorrect DPI images (4K images on mobile) | Avoid |
| 4.5.28 | Identify images with color profile issues (CMYK) | Corrected |
| 4.5.29 | Validate background images optimized (CSS background-image) | Efficient |
| 4.5.30 | Validate icons use SVG | Yes |
| 4.5.31 | Validate SVGs optimized (<5KB ideally) | Minified |
| 4.5.32 | Validate emoji used as Unicode, not PNGs | Yes |
| 4.5.33 | Validate Base64 inline images minimized | Limited use |
| 4.5.34 | Validate <picture> element for art direction | Present where needed |
| 4.5.35 | Identify uncompressed PNGs that should be JPG/WebP | Correct formats |
| 4.5.36 | Validate error handling for failed image loads | Graceful fallback |
| 4.5.37 | Validate OG image optimized and <200KB | Good |
| 4.5.38 | Validate image sitemap generation | Present |
| 4.5.39 | Validate images include semantic meaning (ALT + captions) | Strong |
| 4.5.40 | Compute image performance composite score | >= 90% |
← 4.4 Server-Speed, CDN & Caching Suite4.6 Mobile Performance & Device Adaptation 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).