LCP image size
The LCP element: transfer size and natural / rendered pixel size.
At a glance the headline numbers for LCP image size
The LCP element: transfer size and natural / rendered pixel size.
Distribution & median CLS site count and median CLS at each level of LCP image size — rendered mp
Passing CLS by LCP image size — rendered mp which level passes the CLS most often
LCP image size — rendered mp 0.1 MP. p75 0.2 MP. p99 1.0 MP. At the low end (0–0): CLS 0.00. At the high end (1+): CLS 0.00. computed
Why this matters for the Core Web Vitals, and where to start fixing it
Three numbers describe the LCP image: the bytes over the wire, the pixels in the file, and the pixels actually shown. The gap between the last two is pure waste. An image with far more natural pixels than rendered pixels shipped resolution nobody saw, and the extra bytes stretched the load time.
Right-size first, then compress, then pick the format. Resizing the image to what is displayed saves more than recompressing a wrong-sized original ever will.
Chrome field data from 189,915 sites, representing millions of real page loads. How we measured.