At a glance the headline numbers for ETag present
Whether responses carry ETag validators.
83.4% of sites serve ETag validators.
ETag present sites that have it vs sites that don't
83.4% of sites send ETag headers (158,388 of 189,915). With send: INP 87ms, 94.9% pass. Without: INP 83ms, 93.7% pass. computed
Why this matters for the Core Web Vitals, and where to start fixing it
An ETag is a validator. When a cached file expires, the browser can ask the server whether it changed and get a tiny 304 Not Modified back instead of the whole file. Without a validator, an expired file is downloaded again in full.
Validators matter most for the in-between caching strategies: short TTLs with frequent revisits. For hashed, immutable assets they are redundant because the file never changes under its name. One thing to watch on multi-server setups: default ETags can differ per server, and a mismatched ETag silently turns every revalidation into a full download.
How does this affect the Core Web Vitals?
Having it makes no measurable difference to the LCP: 82% pass with it, 84% without.
Chrome field data from 189,915 sites, representing millions of real page loads. How we measured.