1.5 Performance & Core Web VitalsLowInferred
Images not next-gen format
Serving JPEG or PNG where WebP or AVIF would do means shipping far more bytes than necessary. Modern formats cut image weight substantially with no visible quality loss.
What it is
JPEG/PNG where WebP/AVIF would be lighter.
Why it matters
Larger images slow LCP.
How to fix it
Serve WebP/AVIF with fallbacks.
How to find it on your site
- Audit the page images and note their formats.
- Convert large JPEG and PNG images to WebP or AVIF.
- Serve modern formats with a fallback using the picture element.
- Re-measure image weight after converting.
Cross-reference to ranking and citation factors
Images are usually the heaviest part of a page, so format matters for LCP and total weight. Lighter images load sooner.
Impact
Low. Inferred.
Evidence
Efficient image formats aid LCP. web.dev, Core Web Vitals (Google); Google Search Central, Image SEO best practices
Sources