At a glance the headline numbers for Preloaded fonts
How many fonts the page preloads.
The typical site preloads 0 fonts.
Distribution & median LCP site count and median LCP at each level of preloaded fonts
Passing LCP by preloaded fonts which level passes the LCP most often
Preloaded fonts 0. p75 0. p99 7. Spearman with LCP r = +0.33. At the low end (0): LCP 1.5s. At the high end (>p98): LCP 1.9s. computed
Why this matters for the Core Web Vitals, and where to start fixing it
Fonts are discovered late by design. The browser must download the CSS, parse it, and find rendered text that actually uses an @font-face before it requests the font file. A preload skips that whole chain and starts the download with the HTML.
Preload the one or two fonts that render above-the-fold text, and stop there. Every preloaded font competes with the LCP image for early bandwidth. A preloaded font that is not used above the fold made the page slower for nothing.
How does this affect the Core Web Vitals?
Preloaded fonts correlate with the LCP. With few preloaded fonts, 82% of sites pass the LCP. With many, 71% do. The decline is gradual. There is no point where sites suddenly start failing.
Chrome field data from 189,915 sites, representing millions of real page loads. How we measured.