Image Size Analyzer
Identifies uncompressed images, missing intrinsic dimensions, and assets scaled down via CSS that degrade mobile performance.
What This Metric Means for Your Site
Images are the heaviest part of most websites. Uncompressed images slow down mobile loading, while missing dimensions make the screen jump around while loading.
How to Improve Your Score (Actionable Fixes)
- Always serve images in modern next-gen formats like WebP or AVIF.
- Provide responsive srcset attributes to serve scaled dimensions to mobile viewports.
- Specify explicit width and height attributes on every img tag to lock layout geometry.
Deep-Dive Editorial Guides
Empirical benchmarks and implementationZero CLS Web Design: How to Diagnose and Prevent Layout Shifts
Cumulative Layout Shift degrades user experience and lowers Core Web Vitals pass rates. Learn how aspect ratio containers, font fallback overrides, and fluid clamp typography prevent sudden visual jumps on mobile devices.
WebP vs AVIF vs JPEG: We Tested Real Website Images
Modern image formats promise dramatic bandwidth savings, but browser decode overhead on mobile CPUs is rarely discussed. We tested 100 real website hero images to find the true winner.
Website Teardown #029: Why This High-Growth Shopify Brand Has a 5.1s Mobile LCP
Target: Direct-to-Consumer Beauty Brand (Shopify Plus) (March 2026)
Page Weight Checker
Break down total transfer bytes across JavaScript, CSS, images, and fonts.
Official Performance Standard Documentation
Read the official technical guidelines and documentation governing this metric.
VitalsSniper PRO In-Tab Forensics
Isolate exact DOM elements, generate white label PDF audit summaries, and export outreach lead lists in 50ms from any live Chromium tab.