Core Web Vitals still matter in 2026 — here's what changed
INP replaced FID two years ago and most agency sites still don't measure it. Here's a five-minute read that catches you up.
Google's three Core Web Vitals — LCP, INP, CLS — are still the bar your site is held against. Two years on from INP replacing FID, a surprising number of agencies still ship sites that fail it. Here's the short version.
LCP — Largest Contentful Paint
How fast the biggest above-the-fold thing appears. Target: under 2.5 seconds. Usually killed by un-optimised hero images. Fix: serve AVIF, set explicit width/height, preload the LCP image.
INP — Interaction to Next Paint
How responsive the page feels when you tap or click. Target: under 200ms. Killed by long JavaScript tasks blocking the main thread. Fix: ship less JS, lazy-load below-the-fold widgets, audit your tag manager.
CLS — Cumulative Layout Shift
How much things jump around as the page loads. Target: under 0.1. Killed by images and ads without reserved space. Fix: width/height on every image, font-display swap with size-adjust, no late-injected banners.
“If your agency can't tell you their last project's LCP, INP, and CLS off the top of their head, performance isn't really part of the build.”
How to actually measure
- PageSpeed Insights for a one-shot lab + field score.
- Chrome's Web Vitals extension for live numbers as you click around.
- GA4's Web Vitals report or your host's speed-insights dashboard for the field truth.
Lab scores lie. Field data — what real users on real devices actually experience — is the only number that affects your search rankings. Track it.