Modern Image Formats
Checks images are served as WebP or AVIF — 30-50% smaller than JPEG/PNG.
What this check measures
We fetch page images and check their Content-Type. Flag JPEG/PNG images larger than ~30KB that would benefit from WebP or AVIF conversion.
Why it matters
A 2MB hero JPEG becomes a 500KB WebP with no visible quality loss — ~1.5s faster LCP on mobile. Universal browser support for WebP in 2026.
How our audit detects it
Fetch images, check Content-Type header. Flag large PNG/JPEG with % savings estimate.
Typical findings
- error_outlineHero image as 3MB JPEG — could be 500KB WebP.
- error_outlinePNG used for photo (use JPEG or WebP instead).
- error_outlineNothing served in WebP or AVIF.
How to fix
Convert images to WebP (universal) or AVIF (smaller, needs fallback). Use <picture> with type variants for safety. Next.js Image component handles this automatically.
Copy-paste fix prompt for your stack
Lovable · Cursor · Bolt · v0 · Replit · Windsurf · Claude Code · Base44
Frequently asked questions
WebP or AVIF?expand_more
Want this checked on your site?
Pantra runs the full audit (SEO, Security, GEO, Performance, Schema, Technical, Images) in 10 seconds and generates stack-specific fix prompts.
Scan my siteRelated checks
LCP (Largest Contentful Paint)
Checks Largest Contentful Paint — how fast the main content appears. Target under 2.5s.
PerformanceCLS (Cumulative Layout Shift)
Checks Cumulative Layout Shift — how much the page jumps during load. Target under 0.1.
PerformanceINP (Interaction to Next Paint)
Checks Interaction to Next Paint — responsiveness to clicks/taps. Target under 200ms.
PerformanceFCP (First Contentful Paint)
Checks First Contentful Paint — when the first text or image appears. Target under 1.8s.