At a glance the headline numbers for LCP image format
The image format of the LCP resource.
49.6% of LCP images are JPEG. 26.8% are WebP, 6.2% AVIF.
LCP image format who uses what, and how fast each group loads
Little daylight between the groups: every variant sits near 46ms median INP. computed
Passing INP per LCP image format which group passes the INP most often
No variant stands out: pass rates sit between 97% and 99%. computed
Why this matters for the Core Web Vitals, and where to start fixing it
The format sets the bytes per pixel, and the LCP's load time scales with the bytes. The same hero photo is far smaller as AVIF or WebP than as JPEG, and PNG for photos is the classic mistake: a lossless format doing a lossy job. SVG is its own case, tiny and sharp at any size for logos and illustrations.
Nobody should convert images by hand. An image CDN or a build step serves the best format each browser supports from one source file. The format mix is mostly a measure of which sites have that step.
How does this affect the Core Web Vitals?
LCP image format correlates with the LCP. With GIF, 92% of sites pass the LCP. With Svg+xml, 83% do.
Chrome field data from 94,910 sites, representing millions of real page loads. How we measured.